PAGE 1

University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Summer 2011 1 Effects of Nicotine on R esponding Maintained by Ethanol in Rats Chirag Kulahalli and Dr. Jesse Dallery College of Liberal Arts and Sciences, University of Florida Stimuli associated wit h drugs play an important role in drug consumption. Tobacco and alcohol are two commonly abused drugs that are often used concurrently. The purpose of this experiment was to investigate the effects nicotine might have on the behavio r of rats responding for alcohol and alcohol associated conditioned reinforcers and rats responding for sucrose and sucrose associated conditioned reinforcers. Nicotine produced higher rates of responding compared to vehicle administration for both sucrose and alcohol associated conditioned reinforcers, but not for sucrose or alcohol themselves. In addition, responding for alcohol associated conditioned reinforcers was higher than responding for sucrose associated conditioned reinforcers du ring both nicotine and vehicle administration, although responding for alcohol was higher than responding for sucrose only during vehicle administration and not during nicotine administration. The results extend the finding that nicotine enhances the value of food associated conditioned reinforcers to alcohol associated conditioned reinforcers as well. In addition, alcohol associated conditioned reinforcers may play a greater role in control over behavior than conditioned reinforcers associated with other p rimary reinforcers in a way that cannot be explained by primary reinforcer efficacy. INTRODUCTION Tobacco and alcohol are two widely used drugs in the United States. The social costs of alcohol and tobacco abuse include personal costs, in the form of disease and mortality, as well as significant economic costs (Harwood, Fountain, & Fountain, 1999; Warner, Hodgson, & Carroll, 1999). The importance of the intera ctions between tobacco and alcohol use in individuals has been noted, with alcoholism being 10 times more common in smokers than nonsmokers (DiFranza & Guerrera, 1990; Sharpe & Samson, 2002). The focus of the present experiment is on these interactions. St imuli associated with drugs play an important role in drug taking and addiction. For example, smoking a cigarette delivers not only the pharmacological effects of nicotine, but also the taste, smell, and sight of cigarette smoke. Specifically, drug associa ted stimuli have been shown to act as conditioned reinforcers; a neutral stimulus, after being paired with a primary reinforcer, becomes a conditioned reinforcer that maintains responding even in the absence of a primary reinforcer (Shahan, 2002; Skinner, 1965). In particular, rats will respond for stimuli that were previously associated with alcohol (Shahan & Jimenez Gomez, 2006). There is evidence to suggest that one of the principal functions of nicotine, in addition to being a primary reinforcer itself, is to enhance the reinforcing properties of other stimuli (Caggiula et al., 2002). Previous work has shown that nicotine increases responding maintained by food associated conditioned reinforcers (Raiff & Dallery, 2006). It is possible that such enhanceme nt will be even greater for drug associated stimuli. The so called observing response procedure has been used recently to study drug related conditioned reinforcers (Shahan, 2002; Wyckoff, 1952). This procedure is a novel, rigorous, and data rich approach to study the effect of nicotine on responding for alcohol associated stimuli. In the observing response procedure, a specific stimulus, known as the S+, is paired with periods when a primary reinforcer (e.g., alcohol) is available, while a second stimulus known as the S is paired with periods of extinction, when no reinforcer is available. Rats are housed in an operant chamber with two levers. Responses on one lever produce unsignaled reinforcement or extinction, i.e. a mixed schedule. Responses on the other lever (observing responses) briefly produce the stimulus associated with reinforcement (S+) or the stimulus associated with extinction (S ), depending on which schedule is in effect. The S+ is typically considered a conditioned reinforcer, since obse rving is primarily maintained by the S+ alone (Dinsmoor, 1983). The observing response procedure allows researchers to analyze three relevant responses: observing responses, responses for the primary reinforcer, and responses during extinction. The focus o f this experiment was to investigate the effect of nicotine on responding for alcohol as well as alcohol associated conditioned reinforcers. Based on previous research, we made the following predictions: (a) pretreatment with nicotine would increase respon ding by conditioned reinforcers, whether the stimuli were paired with sucrose or sucrose plus alcohol; (b) these increases

PAGE 2

CHIRAG KULAHALLI & D R JESSE D ALLERY University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Summer 2011 2 would be greater for alcohol cues than for sucrose cues; (c) these increases would not be due to general increases in activity; that is, we did not expect to see increases in responding during periods of extinction ; and (d) nicotine would not increase responding maintained by sucrose, but it might increase responding maintained by alcohol. This last prediction was more tentative, since studies on the effect of nicotine on alcohol administration have produced mixed re sults (Sharpe & Samson, 2002). METHOD Subjects Twelve experimentally nave male rats, subjects 311 322, were used in the experiment (subjects 311, 313, 314, 318, 320, and 322 assigned alcohol as the primary reinforcer, and subjects 312, 315, 316, 317, 319, and 321 assigned sucrose as the primary reinforcer), but one rat from the sucrose group (subject 321) was euthanized owing to a cancerous growth it developed. Therefore, the results presented are only for the remaining eleven rats. The rats were housed in individual cages on a 12 hour light cycle. The rats were maintained at 90% of their free feeding body weights, fed with standard pelleted rat chow, and received free access to water except for four hours prior to each experimental session. Apparatus and Materials Experimental sessions were conducted in four MED (Model ENV 007; 30.48 cm long X 24.13 cm wide X 29.21 cm high) contained in separate sound attenuating cubicles. Back walls, ceilings, and doors of operant chambers were clear polycarbonate, and intelligence panels, sidewalls, grid were stainless steel. Intelligence panels were equipped with 2 response levers, which were separated by a food receptacle (5 cm x 5 cm x 3 cm ) in which a solenoid operated dipper delivered liquid solutions. The dipper allowed 3 s of access to 0.1 mL of liquid. Three LEDs (red, yellow, and green ; 0.8 cm in diameter) were positioned 7 cm above each lever and 0.7 cm apart. The chamber was also equ ipped with a houselight (28 V) 1.5 cm from the ceiling. MED PC software and hardware (MED Associates) w ere used to program experimental sessions and collect and analyze data. A 5% sucrose solution was used as the primary reinforcer for all rats within the sucrose group except subject 317, which received a 10% sucrose solution in order to maintain sufficient rates of responding. A 95% stock solution of ethanol was used to make a 10% ethanol/5% sucrose solution for all rats in the alcohol group. During nicot ine administration, nicotine (Sigma, St. Louis, MO) dissolved in potassium phosphate was used. Procedure Experimental sessions were conducted daily at approximately the same time. During lever training, a lever press on either lever would result in 3 s access to the dipper filled with 5% sucrose solution, accompanied by an audible click. In addition, the three LEDs above each lever, which were normally illuminated, were extinguished while the dipper remained accessible. Discrimination Training After all rats were reliably pressing levers for sucrose solution, discrimination training began. Each session lasted 30 min. In the discrimination training sessions, only the right lever was active. A multiple variable interval (VI) 30 s extinction schedule was in effect. During the VI component, a dipper delivery was available, on average, every 30 s. Rats in the sucrose group continued to receive 5% sucrose as the reinforcer, while rats in the alcohol group started with 5% sucrose and began to receive a 2% ethanol /5% sucrose solution on the fourteenth session. The concentration of ethanol was increased from 2% over several sessions in this order: 2%, 4%, 6%, and finally 10% by the seventeenth session. During extinction, lever presses never resulted in a dipper deli very. Stimuli corresponding to both components were present at all times during discrimination training : during the VI component, the houselight was continuously illuminated (S+), while during extinction, the houselight rapidly blinked (S ). The two compon ents alternated during each session, with each component lasting an average of 60 s. In order to prevent responding during the presence of the S a DRO (differential reinforcement of other behavior) was implemented; in order for the extinction component t o switch to the VI component, 5 s without a lever press was required. Each rat had 55 discrimination training sessions before beginning observing response sessions. Observing Response During the observing response sessions, the right lever functioned as it did during the discrimination training sessions. The left lever functioned as the observing response lever; that is, presses on the left lever produce d 10 s of either the S+ or S depending on which component was in effect. The S+ and S were not availab le unless the responses were made on the left lever, unlike the discrimination training sessions. For the first seven sessions, the stimulus presentations were available on a fixed ratio (FR) 1 schedule, in which every response resulted in a stimulus prese ntation; afterwards, they were available on a VI 15 s schedule. The DRO was removed for the observing response sessions. For the first 18 observing response sessions, no nicotine or vehicle was administered, and the last six sessions during this phase comp rise the baseline data for the experiment.

PAGE 3

E FFECTS OF NICOTINE ON R ESPONDING MAINTAINED BY E THANOL IN R ATS University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Summer 2011 3 Dru g Administration Following the baseline phase, drug administration began, with subcutaneous injections given immediately prior to experimental sessions. Doses were 0.3 mg/kg for both nicotine and vehicle. Six s ubjects received nicotine injections for their first six sessions and vehicle injections for their next six sessions, while five received vehicle injections for the first six sessions and nicotine for the next six; this order was counterbalanced across bot h sucrose and alcohol groups. Two subjects, 316 and 320, received pre session nicotine on only five days instead of six. RESULTS Data Analysis Data from drug administration sessions were used for analysis. The three types of responses analyzed were o bservi ng responses, primary reinforcer maintained responses, and extinction responses. In addition, response rates for vehicle administration and nicotine administration were compared. This resulted in six different categories of responses (observing responses with vehicle, observing responses with nicotine, primary reinforcer maintained responses with vehicle, etc.). Mean response rates for sucrose and alcohol groups were calculated for each category of response. Mean response rates for vehicle sessions and nicotine sessions for each category of response were also calculated. Independent t tests were used to compare mean response rates for each category of response between alcohol and sucrose groups. Paired t tests were used to compare the mean response rates of vehicle sessions and nicotine se ssions for each category of response. Alpha was also set at 0.05 for all statistical tests. Observing Responses Observing response rates were calculated using responses that occurred only when neither stimulus was present, i.e. during the mixed schedule. F igure 1 shows mean response rates for alcohol and sucrose groups for vehicle and nicotine administration. Observing response rates were significantly higher for the alcohol group compared to the sucrose group during vehicle administration, t (62) = 2.84, p = 0.003. In addition, these rates were significantly higher for the alcohol group during nicotine administration, t (62) = 3.35, p = 0.001. Nicotine administration resulted in a statistically significant increase compared to vehicle in observing response ra te for both sucrose, t (28) = 3.31, p = 0.001, and alcohol groups, t (34) = 4.56, p = 0.000. Figure 1 : Average response rates for both groups, during both vehicle and nicotine administration, are shown. Error bars represent standard deviation. Primary R einforcer M aintained Re sponses Only responses that occurred in the presence of the S+ were used in these calculations. Figure 2 shows mean response rates for the primary reinforcer for both sucrose and alcohol groups during both vehicle and nicotine administration. Response rate s during vehicle administration for the alcohol group were significantly higher than for the sucrose group, t (62) = 2.39, p = 0.010. The response rates for the alcohol group were not significantly higher than for the sucrose group during

PAGE 4

CHIRAG KULAHALLI & D R JESSE D ALLERY University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Summer 2011 4 nicotine administr ation, t (62) = 1.33, p = 0.095, however. Nicotine administration did not increase responding for either sucrose or alcohol; in fact, there was a small but statistically significant decrease in responding for alcohol during nicotine administration, t (34) = 2.15, p = 0.020. Extinction Responses Only responses that occurred in the presence of the S were used for these calculations. Figure 3 shows mean response rates during extinction for both groups, with vehicle and nicotine administration. During vehicle ad ministration, response rates during extinction were significantly higher for the alcohol group than for the sucrose group, t(62) = 2.50, p = 0.007. They were not significantly different during nicotine administration. Nicotine administration did not signif icantly increase response rates during extinction for either the sucrose group or the alcohol group. Figure 2. Average response rates for the primary reinforcer are shown. Error bars represent standard deviation. Figure 3. A verage response rates during extinction are shown. Error bars represent standard deviation

PAGE 5

E FFECTS OF NICOTINE ON R ESPONDING MAINTAINED BY E THANOL IN R ATS University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Summer 2011 5 DISCUSSION Both sucrose and alcohol groups showed statistically significant increases in observing response rates with nicotine administration, as predicted. This extends previous findings that nicotine increases responding maintained by sucrose pellet associated con ditioned reinforcers to conditioned reinforcers associated with liquid sucrose solution and alcohol (Raiff & Dallery, 2006). In addition, observing response rates were significantly higher for the alcohol group during both vehicle and nicotine administrati on, suggesting that alcohol associated stimuli may play an important role in alcohol consumption. Responding for alcohol itself was significantly higher than for sucrose during vehicle administration, but not during nicotine administration. Therefore, the higher observing response rates during nicotine administration cannot be explained by higher primary reinforcer efficacy. These findings support the idea that nicotine enhances the value of conditioned reinforcers. Thus, the results of this experiment supp ort the idea that nicotine serves to enhance the reinforcing properties of other stimuli (Caggiula et al., 2002). However, in this experiment, nicotine did not appear to enhance the reinforcing properties of either primary reinforcer. In addition, it did n ot increase responding during extinction for either group. Therefore, observed increases in observing response rate with nicotine do not appear to be due to general behavioral activation. Previous work in our laboratory has produced inconclusive findings o n the effect of nicotine on responding for primary reinforcers. Raiff and Dallery (2006) found that only chronic administration of nicotine produced increases in responding for sucrose pellets, while acute administration did not. Interestingly, nicotine ad ministration slightly decreased responding maintained by alcohol. Previous studies have produced mixed findings on this topic. Sharpe and Samson also found that nicotine decreased responding for alcohol (2002), while others found that nicotine administrati on increased responding for alcohol (Blomqvist, Ericson, Johnson, Engel, & Soderpalm, 1996). The strain of rat used may be a factor; we used Long Evans rats in the present experiment, as did Sharpe and Samson, but Blomqvist et al. used Wistar rats. It shou ld be noted that the lack of an increase in responding for either primary reinforcer during nicotine administration effect (Bellinger, Cepeda Benito, & Wellman, 2003). Studying the interactions betwee n nicotine and other non caloric drugs might shed more light on this issue. The results of this study have implications for individuals who consume both alcohol and tobacco products. By increasing the value of alcohol cues, nicotine may play a role in rela pse in alcoholics, for example. More research on the interaction of nicotine and other drugs, perhaps besides alcohol, should be conducted in order to further our understanding on the concurrent use of multiple drugs and its effects on behavior. In this ex periment, only one dose of nicotine and one concentration of alcohol were used; using multiple dosages and concentrations might produce more information on nicotine alcohol interactions. For example, different concentrations of alcohol might affect results by changing the overall consumption of alcohol by rats. Evidence for the interaction between nicotine and alcohol exists at the neurobiological level. The nicotinic acetylcholine receptor (nAChR), a ligand gated ionotropic receptor, is the focus of much research. The nAChR is opened by the neurotransmitter acetylcholine as well as by nicotine. This receptor is found on the mesolimbic dopamine neurons, which are involved in brain reward function and the reinforcing properties of alcohol, and alcohol may s erve as a co agonist to the receptor (Larsson & Engel, 2004). The centrally acting nAChR antagonist, mecamylamine, has been shown to decrease dopamine overflow initiated by alcohol in the nucleus accumbens as well as to decrease alcohol consumption in rats (Larsson & Engel, 2004; Steensland, Simms, Holgate, Richards, & Bartlett, 2007). In addition, varenicline, a partial agonist of the nAChR and a treatment for smoking cessation, has been suggested as a potential treatment for decreasing alcohol consumption since it was found to selectively decrease alcohol consumption (Kamens, Anderson, & Piccioto, 2010; Steensland et al., 2007). Although nicotine was not found to increase responding for alcohol in this experiment, the involvement of the nAChR in the neur onal pathways of both nicotine and alcohol suggests an avenue of further research in order to evaluate the interactions between the behavioral effects of both drugs. One such area to investigate is the potential role that nAChRs could play regarding the st imuli associated with nicotine and alcohol. For example, further research might investigate the effect of mecamylamine or associated cues. REFERENCES Bel linger, L., Cepeda Benito, A., & Wellman, P. J. (2003). Meal patterns in male rats during and after intermittent nicotine administration. Pharmacology, Biochemistry, and Behavior 74(2), 495 504. Blomqvist, O., Ericson, M., Johnson, D. H., Engel, J. A., & Soderpalm, B. (1996). Voluntary ethanol intake in the rat: Effects of nicotinic acetylcholine receptor blockade or subchronic nicotine treatment. European Journal of Pharmacology 314(3), 257 267. Caggiula, A. R., Donny, E. C., Chaudhri, N., Perkins, K. A., Evans Martin, F. F., & Sved, A. F. (2002). Importance of nonpharmacological factors in nicotine self administration. Physiology & Behavior 77(4 5), 683 687. DiFranza, J. R. and Guerrera, M. P. (1990). Alcoholism and smoking. J Stud Alcohol 51, 130 135.

PAGE 6

CHIRAG KULAHALLI & D R JESSE D ALLERY University of Florida | Journal of Undergraduate Research | Volume 12 Issue 3 | Summer 2011 6 Dinsmoor, J. A. (1983). Observing and conditioned reinforcement. Behavioral and Brain Sciences 6, 693 728. Harwood, H. J., Fountain, D., & Fountain, G. (1999). Economic cost of alcohol and drug abuse in the united states, 1992: A report. Addiction (Abingdon, England), 94(5), 631 635. Kamens, H. M., Andersen, J., & Picciotto, M. R. (2010). Modulation of ethanol consumption by genetic and pharmacological manipulation of nicotinic acetylcholine receptors in mice s Psychopharmacology 208(4), 613 26 Larsson, A., & Engel, J. A. (2004). Neurochemical and behavioral studies on ethanol and nicotine interactions. Neuroscience and Biobehavioral Reviews 27(8), 713 720. Raiff, B. R., & Dallery, J. (2006). Effects of acute and chronic nicotine on res ponses maintained by primary and conditioned reinforcers in rats. Experimental and Clinical Psychopharmacology 14(3), 296 305. Shahan, T. A. (2002). The observing response procedure: A novel method to study drug associated conditioned reinforcement. Expe rimental and Clinical Psychopharmacology 10(1), 3 9. Shahan, T. A., & Jimenez Gomez, C. (2006). Effects of self administered alcohol concentration on the frequency and persistence of rats' attending to alcohol cues. Behavioural Pharmacology 17(3), 201 2 11. Sharpe, A. L., & Samson, H. H. (2002). Repeated nicotine injections decrease operant ethanol self administration. Alcohol (Fayetteville, N.Y.), 28(1), 1 7. Skinner, B. F. (1965). Science and Human Behavior New York, NY: The Free Press. Steensland, P., Simms, J. A., Holgate, J., Richards, J. K., & Bartlett, S. E. (2007). Varenicline, an alpha4beta2 nicotinic acetylcholine receptor partial agonist, selectively decreases ethanol consumption and seeking. Proceedings of the National Academy of Sciences o f the United States of America 104(30), 12518 12523. Warner, K. E., Hodgson, T. A., & Carroll, C. E. (1999). Medical costs of smoking in the United States: Estimates, their validity, and their implications. Tobacco Control 8(3), 290 300. Wyckoff, L. B. (1952). The role of observing responses in discrimination learning. Psychological Review 59, 431 442.


Summer Focus on Medical Research : Effects of Nicotine on Responding Maintained by Ethanol in Rats
ALL VOLUMES CITATION THUMBNAILS PDF VIEWER PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00091523/00598
 Material Information
Title: Summer Focus on Medical Research : Effects of Nicotine on Responding Maintained by Ethanol in Rats
Series Title: Journal of Undergraduate Research
Physical Description: Serial
Language: English
Creator: Kulahalli, Chirag
Dallery, Jesse
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011
 Subjects
Genre: serial   ( sobekcm )
 Notes
Abstract: Stimuli associated with drugs play an important role in drug consumption. Tobacco and alcohol are two commonly abused drugs that are often used concurrently. The purpose of this experiment was to investigate the effects nicotine might have on the behavior of rats responding for alcohol and alcohol-associated conditioned reinforcers and rats responding for sucrose and sucrose-associated conditioned reinforcers. Nicotine produced higher rates of responding compared to vehicle administration for both sucrose- and alcohol-associated conditioned reinforcers, but not for sucrose or alcohol themselves. In addition, responding for alcohol-associated conditioned reinforcers was higher than responding for sucrose-associated conditioned reinforcers during both nicotine and vehicle administration, although responding for alcohol was higher than responding for sucrose only during vehicle administration and not during nicotine administration. The results extend the finding that nicotine enhances the value of food-associated conditioned reinforcers to alcohol-associated conditioned reinforcers as well. In addition, alcohol-associated conditioned reinforcers may play a greater role in control over behavior than conditioned reinforcers associated with other primary reinforcers in a way that cannot be explained by primary reinforcer efficacy.
 Record Information
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: sobekcm - UF00091523_00598
System ID: UF00091523:00598

Downloads

This item has the following downloads:

( PDF )


Full Text



Effects of Nicotine on Responding Maintained by Ethanol in
Rats

Chirag Kulahalli and Dr. Jesse Dallery

College of Liberal Arts and Sciences, University of Florida

Stimuli associated with drugs play an important role in drug consumption. Tobacco and alcohol are two commonly abused drugs that
are often used concurrently. The purpose of this experiment was to investigate the effects nicotine might have on the behavior of rats
responding for alcohol and alcohol-associated conditioned reinforcers and rats responding for sucrose and sucrose-associated
conditioned reinforcers. Nicotine produced higher rates of responding compared to vehicle administration for both sucrose- and
alcohol-associated conditioned reinforcers, but not for sucrose or alcohol themselves. In addition, responding for alcohol-associated
conditioned reinforcers was higher than responding for sucrose-associated conditioned reinforcers during both nicotine and vehicle
administration, although responding for alcohol was higher than responding for sucrose only during vehicle administration and not
during nicotine administration. The results extend the finding that nicotine enhances the value of food-associated conditioned
reinforcers to alcohol-associated conditioned reinforcers as well. In addition, alcohol-associated conditioned reinforcers may play a
greater role in control over behavior than conditioned reinforcers associated with other primary reinforcers in a way that cannot be
explained by primary reinforcer efficacy.


INTRODUCTION

Tobacco and alcohol are two widely-used drugs in the
United States. The social costs of alcohol and tobacco
abuse include personal costs, in the form of disease and
mortality, as well as significant economic costs (Harwood,
Fountain, & Fountain, 1999; Warner, Hodgson, & Carroll,
1999). The importance of the interactions between tobacco
and alcohol use in individuals has been noted, with
alcoholism being 10 times more common in smokers than
nonsmokers (DiFranza & Guerrera, 1990; Sharpe &
Samson, 2002). The focus of the present experiment is on
these interactions.
Stimuli associated with drugs play an important role in
drug-taking and addiction. For example, smoking a
cigarette delivers not only the pharmacological effects of
nicotine, but also the taste, smell, and sight of cigarette
smoke. Specifically, drug-associated stimuli have been
shown to act as conditioned reinforcers; a neutral stimulus,
after being paired with a primary reinforcer, becomes a
conditioned reinforcer that maintains responding even in
the absence of a primary reinforcer (Shahan, 2002;
Skinner, 1965). In particular, rats will respond for stimuli
that were previously associated with alcohol (Shahan &
Jimenez-Gomez, 2006). There is evidence to suggest that
one of the principal functions of nicotine, in addition to
being a primary reinforcer itself, is to enhance the
reinforcing properties of other stimuli (Caggiula et al.,
2002). Previous work has shown that nicotine increases
responding maintained by food-associated conditioned
reinforcers (Raiff & Dallery, 2006). It is possible that such


enhancement will be even greater for drug-associated
stimuli.
The so-called observing response procedure has been
used recently to study drug-related conditioned reinforcers
(Shahan, 2002; Wyckoff, 1952). This procedure is a novel,
rigorous, and data-rich approach to study the effect of
nicotine on responding for alcohol-associated stimuli. In
the observing response procedure, a specific stimulus,
known as the S+, is paired with periods when a primary
reinforcer (e.g., alcohol) is available, while a second
stimulus, known as the S-, is paired with periods of
extinction, when no reinforcer is available. Rats are housed
in an operant chamber with two levers. Responses on one
lever produce unsignaled reinforcement or extinction, i.e. a
mixed schedule. Responses on the other lever (observing
responses) briefly produce the stimulus associated with
reinforcement (S+) or the stimulus associated with
extinction (S-), depending on which schedule is in effect.
The S+ is typically considered a conditioned reinforcer,
since observing is primarily maintained by the S+ alone
(Dinsmoor, 1983).
The observing response procedure allows researchers to
analyze three relevant responses: observing responses,
responses for the primary reinforcer, and responses during
extinction. The focus of this experiment was to investigate
the effect of nicotine on responding for alcohol as well as
alcohol-associated conditioned reinforcers. Based on
previous research, we made the following predictions: (a)
pretreatment with nicotine would increase responding by
conditioned reinforcers, whether the stimuli were paired
with sucrose or sucrose plus alcohol; (b) these increases


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 3 I Summer 2011
1





CHIRAG KULAHALLI & DR. JESSE DALLERY


would be greater for alcohol cues than for sucrose cues; (c)
these increases would not be due to general increases in
activity; that is, we did not expect to see increases in
responding during periods of extinction; and (d) nicotine
would not increase responding maintained by sucrose, but
it might increase responding maintained by alcohol. This
last prediction was more tentative, since studies on the
effect of nicotine on alcohol administration have produced
mixed results (Sharpe & Samson, 2002).


METHOD


Procedure

Experimental sessions were conducted daily at
approximately the same time. During lever training, a lever
press on either lever would result in 3 s access to the dipper
filled with 5% sucrose solution, accompanied by an audible
click. In addition, the three LEDs above each lever, which
were normally illuminated, were extinguished while the
dipper remained accessible.


Discrimination Training


Subjects

Twelve experimentally naive male rats, subjects 311-
322, were used in the experiment (subjects 311, 313, 314,
318, 320, and 322 assigned alcohol as the primary
reinforcer, and subjects 312, 315, 316, 317, 319, and 321
assigned sucrose as the primary reinforcer), but one rat
from the sucrose group (subject 321) was euthanized owing
to a cancerous growth it developed. Therefore, the results
presented are only for the remaining eleven rats. The rats
were housed in individual cages on a 12-hour light cycle.
The rats were maintained at 90% of their free-feeding body
weights, fed with standard pelleted rat chow, and received
free access to water except for four hours prior to each
experimental session.

Apparatus and Materials

Experimental sessions were conducted in four MED
Associates (East Fairfield, VT) extra tall operant chambers
(Model ENV 007; 30.48 cm long X 24.13 cm wide X 29.21
cm high) contained in separate sound-attenuating cubicles.
Back walls, ceilings, and doors of operant chambers were
clear polycarbonate, and intelligence panels, sidewalls, grid
floors, and drop pans were stainless steel. Intelligence
panels were equipped with 2 response levers, which were
separated by a food receptacle (5 cm x 5 cm x 3 cm) in
which a solenoid operated dipper delivered liquid
solutions. The dipper allowed 3 s of access to 0.1 mL of
liquid. Three LEDs (red, yellow, and green; 0.8 cm in
diameter) were positioned 7 cm above each lever and 0.7
cm apart. The chamber was also equipped with a
houselight (28 V) 1.5 cm from the ceiling. MED-PC
software and hardware (MED Associates) were used to
program experimental sessions and collect and analyze
data.
A 5% sucrose solution was used as the primary
reinforcer for all rats within the sucrose group except
subject 317, which received a 10% sucrose solution in
order to maintain sufficient rates of responding. A 95%
stock solution of ethanol was used to make a 10%
ethanol/5% sucrose solution for all rats in the alcohol
group. During nicotine administration, nicotine (Sigma, St.
Louis, MO) dissolved in potassium phosphate was used.


After all rats were reliably pressing levers for sucrose
solution, discrimination training began. Each session lasted
30 min. In the discrimination training sessions, only the
right lever was active. A multiple variable interval (VI) 30
s-extinction schedule was in effect. During the VI
component, a dipper delivery was available, on average,
every 30 s. Rats in the sucrose group continued to receive
5% sucrose as the reinforcer, while rats in the alcohol
group started with 5% sucrose and began to receive a 2%
ethanol/5% sucrose solution on the fourteenth session. The
concentration of ethanol was increased from 2% over
several sessions in this order: 2%, 4%, 6%, and finally 10%
by the seventeenth session. During extinction, lever presses
never resulted in a dipper delivery. Stimuli corresponding
to both components were present at all times during
discrimination training: during the VI component, the
houselight was continuously illuminated (S+), while during
extinction, the houselight rapidly blinked (S-). The two
components alternated during each session, with each
component lasting an average of 60 s. In order to prevent
responding during the presence of the S-, a DRO
(differential reinforcement of other behavior) was
implemented; in order for the extinction component to
switch to the VI component, 5 s without a lever press was
required. Each rat had 55 discrimination training sessions
before beginning observing response sessions.

Observing Response

During the observing response sessions, the right lever
functioned as it did during the discrimination training
sessions. The left lever functioned as the observing
response lever; that is, presses on the left lever produced 10
s of either the S+ or S-, depending on which component
was in effect. The S+ and S- were not available unless the
responses were made on the left lever, unlike the
discrimination training sessions. For the first seven
sessions, the stimulus presentations were available on a
fixed ratio (FR) 1 schedule, in which every response
resulted in a stimulus presentation; afterwards, they were
available on a VI 15 s schedule. The DRO was removed for
the observing response sessions. For the first 18 observing
response sessions, no nicotine or vehicle was administered,
and the last six sessions during this phase comprise the
baseline data for the experiment.


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 3 1 Summer 2011
2





EFFECTS OF NICOTINE ON RESPONDING MAINTAINED BY ETHANOL IN RATS


Drug Administration

Following the baseline phase, drug administration began,
with subcutaneous injections given immediately prior to
experimental sessions. Doses were 0.3 mg/kg for both
nicotine and vehicle. Six subjects received nicotine
injections for their first six sessions and vehicle injections
for their next six sessions, while five received vehicle
injections for the first six sessions and nicotine for the next
six; this order was counterbalanced across both sucrose and
alcohol groups. Two subjects, 316 and 320, received pre-
session nicotine on only five days instead of six.

RESULTS

Data Analysis

Data from drug administration sessions were used for
analysis. The three types of responses analyzed were
observing responses, primary reinforcer-maintained
responses, and extinction responses. In addition, response
rates for vehicle administration and nicotine administration
were compared. This resulted in six different categories of
responses (observing responses with vehicle, observing
responses with nicotine, primary reinforcer-maintained
responses with vehicle, etc.). Mean response rates for
sucrose and alcohol groups were calculated for each


3.5-

3.0-




0
S2.5

o


S2.0-
I "*o


category of response. Mean response rates for vehicle
sessions and nicotine sessions for each category of
response were also calculated. Independent t-tests were
used to compare mean response rates for each category of
response between alcohol and sucrose groups. Paired t-tests
were used to compare the mean response rates of vehicle
sessions and nicotine sessions for each category of
response. Alpha was also set at 0.05 for all statistical tests.

Observing Responses

Observing response rates were calculated using
responses that occurred only when neither stimulus was
present, i.e. during the mixed schedule. Figure 1 shows
mean response rates for alcohol and sucrose groups for
vehicle and nicotine administration. Observing response
rates were significantly higher for the alcohol group
compared to the sucrose group during vehicle
administration, t(62)= 2.84, p = 0.003. In addition, these
rates were significantly higher for the alcohol group during
nicotine administration, t(62)= 3.35, p = 0.001. Nicotine
administration resulted in a statistically significant increase
compared to vehicle in observing response rate for both
sucrose, t(28) = 3.31, p = 0.001, and alcohol groups, t(34)
= 4.56, p = 0.000.


S vehicle e
I Nicotine
% vehicle
Cl rJicotine


Sucrose Group Alcohol Group


Figure 1: Average response rates for both groups, during both vehicle and nicotine
administration, are shown. Error bars represent standard deviation.


Primary Reinforcer-Maintained Responses

Only responses that occurred in the presence of the S+
were used in these calculations. Figure 2 shows mean
response rates for the primary reinforcer for both sucrose
and alcohol groups during both vehicle and nicotine


administration. Response rates during vehicle
administration for the alcohol group were significantly
higher than for the sucrose group, t(62) = 2.39, p = 0.010.
The response rates for the alcohol group were not
significantly higher than for the sucrose group during


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 3 1 Summer 2011
3





CHIRAG KULAHALLI & DR. JESSE DALLERY


nicotine administration, t(62) = 1.33, p = 0.095, however.
Nicotine administration did not increase responding for
either sucrose or alcohol; in fact, there was a small but
statistically significant decrease in responding for alcohol
during nicotine administration, t(34) = 2.15, p = 0.020.

Extinction Responses

Only responses that occurred in the presence of the S-
were used for these calculations. Figure 3 shows mean




35

30

S25-


0 20
0

G) 15

10


response rates during extinction for both groups, with
vehicle and nicotine administration. During vehicle
administration, response rates during extinction were
significantly higher for the alcohol group than for the
sucrose group, t(62) = 2.50, p = 0.007. They were not
significantly different during nicotine administration.
Nicotine administration did not significantly increase
response rates during extinction for either the sucrose
group or the alcohol group.



















SucroseNehicle
ii Sucrose/Nicotine
S AlcoholNehicle
/ 2 Alcohol/Nicotine


Sucrose Group


Alcohol Group


Figure 2. Average response rates for the primary reinforcer are shown. Error bars represent
standard deviation.


35

30

E 25
I)
U 20
C
020
U,
a) 15
a)
1 10


SucroseNehicle
SSucrose/Nicotine
Alcohol/Vehicle
Z771 Alcohol/Nicotine


Sucrose Group


Alcohol Group


Figure 3. Average response rates during extinction are shown. Error bars represent
standard deviation.

University of Florida I Journal of Undergraduate Research I Volume 12, Issue 3 I Summer 2011
4





EFFECTS OF NICOTINE ON RESPONDING MAINTAINED BY ETHANOL IN RATS


DISCUSSION

Both sucrose and alcohol groups showed statistically
significant increases in observing response rates with
nicotine administration, as predicted. This extends previous
findings that nicotine increases responding maintained by
sucrose pellet-associated conditioned reinforcers to
conditioned reinforcers associated with liquid sucrose
solution and alcohol (Raiff & Dallery, 2006). In addition,
observing response rates were significantly higher for the
alcohol group during both vehicle and nicotine
administration, suggesting that alcohol-associated stimuli
may play an important role in alcohol consumption.
Responding for alcohol itself was significantly higher than
for sucrose during vehicle administration, but not during
nicotine administration. Therefore, the higher observing
response rates during nicotine administration cannot be
explained by higher primary reinforcer efficacy.
These findings support the idea that nicotine enhances
the value of conditioned reinforcers. Thus, the results of
this experiment support the idea that nicotine serves to
enhance the reinforcing properties of other stimuli
(Caggiula et al., 2002). However, in this experiment,
nicotine did not appear to enhance the reinforcing
properties of either primary reinforcer. In addition, it did
not increase responding during extinction for either group.
Therefore, observed increases in observing response rate
with nicotine do not appear to be due to general behavioral
activation.
Previous work in our laboratory has produced
inconclusive findings on the effect of nicotine on
responding for primary reinforcers. Raiff and Dallery
(2006) found that only chronic administration of nicotine
produced increases in responding for sucrose pellets, while
acute administration did not. Interestingly, nicotine
administration slightly decreased responding maintained by
alcohol. Previous studies have produced mixed findings on
this topic. Sharpe and Samson also found that nicotine
decreased responding for alcohol (2002), while others
found that nicotine administration increased responding for
alcohol (Blomqvist, Ericson, Johnson, Engel, &
Soderpalm, 1996). The strain of rat used may be a factor;
we used Long-Evans rats in the present experiment, as did
Sharpe and Samson, but Blomqvist et al. used Wistar rats.
It should be noted that the lack of an increase in responding
for either primary reinforcer during nicotine administration
in this experiment might be due to nicotine's anorectic


REFERENCES
Bellinger, L., Cepeda-Benito, A., & Wellman, P. J. (2003). Meal patterns in male
rats during and after intermittent nicotine administration.
Biochemistry, andBehavior, 74(2), 495-504.
Blomqvist,, Ericson, M., Johnson, D. H., Engel, J. A., & Soderpalm, B.
(1996). Voluntary ethanol intake in the rat: Effects of nicotinic acetylcholine


effect (Bellinger, Cepeda-Benito, & Wellman, 2003).
Studying the interactions between nicotine and other non-
caloric drugs might shed more light on this issue.
The results of this study have implications for
individuals who consume both alcohol and tobacco
products. By increasing the value of alcohol cues, nicotine
may play a role in relapse in alcoholics, for example. More
research on the interaction of nicotine and other drugs,
perhaps besides alcohol, should be conducted in order to
further our understanding on the concurrent use of multiple
drugs and its effects on behavior. In this experiment, only
one dose of nicotine and one concentration of alcohol were
used; using multiple dosages and concentrations might
produce more information on nicotine-alcohol interactions.
For example, different concentrations of alcohol might
affect results by changing the overall consumption of
alcohol by rats.
Evidence for the interaction between nicotine and
alcohol exists at the neurobiological level. The nicotinic
acetylcholine receptor (nAChR), a ligand-gated ionotropic
receptor, is the focus of much research. The nAChR is
opened by the neurotransmitter acetylcholine as well as by
nicotine. This receptor is found on the mesolimbic
dopamine neurons, which are involved in brain reward
function and the reinforcing properties of alcohol, and
alcohol may serve as a co-agonist to the receptor (Larsson
& Engel, 2004). The centrally acting nAChR antagonist,
mecamylamine, has been shown to decrease dopamine
overflow initiated by alcohol in the nucleus accumbens as
well as to decrease alcohol consumption in rats (Larsson &
Engel, 2004; Steensland, Simms, Holgate, Richards, &
Bartlett, 2007). In addition, varenicline, a partial agonist of
the nAChR and a treatment for smoking cessation, has
been suggested as a potential treatment for decreasing
alcohol consumption, since it was found to selectively
decrease alcohol consumption (Kamens, Anderson, &
Piccioto, 2010; Steensland et al., 2007).
Although nicotine was not found to increase responding
for alcohol in this experiment, the involvement of the
nAChR in the neuronal pathla\\ of both nicotine and
alcohol suggests an avenue of further research in order to
evaluate the interactions between the behavioral effects of
both drugs. One such area to investigate is the potential
role that nAChRs could play regarding the stimuli
associated with nicotine and alcohol. For example, further
research might investigate the effect of mecamylamine or
varenicline on rats' responding for alcohol-associated cues.


receptor blockade or subchronic nicotine treatment. European Journal of
S. 314(3), 257-267.
Caggiula, A. R., Donny, E. C., Chaudhri, N., Perkins, K. A., Evans-Martin, F. F.,
& Sved, A. F. (2002). Importance of nonpharmacological factors in nicotine
self-administration. 1 & Behavior, 77(4-5), 683-687.
DiFranza, J. R. and Guerrera, M. P. (1990). Alcoholism and smoking. J Stud
Alcohol, 51, 130-135.


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 3 I Summer 2011
5





CHIRAG KULAHALLI & DR. JESSE DALLERY


Dinsmoor, J. A. (1983). Observing and conditioned reinforcement. Behavioral
andBrain Sciences, 6, 693-728.

Harwood, H. J., Fountain, D., & Fountain, G. (1999). Economic cost of alcohol
and drug abuse in the united states, 1992: A report. Addiction (Abingdon,
England), 94(5), 631-635.

Kamens, H. M., Andersen, J., & Picciotto, M. R. (2010). Modulation of ethanol
consumption by genetic and pharmacological manipulation of nicotinic
acetylcholine receptors in mices. .. 2.'. -I 613-26

Larsson, A., & Engel, J. A. (2004). Neurochemical and behavioral studies on
ethanol and nicotine interactions. Neuroscience and Biobehavioral Reviews,
27(8), 713-720.

Raiff, B. R., & Dallery, J. (2006). Effects of acute and chronic nicotine on
responses maintained by primary and conditioned reinforcers in rats.
Experimental and Clinical 14(3), 296-305.

Shahan, T. A. (2002). The observing-response procedure: A novel method to
study drug-associated conditioned reinforcement. Experimental and Clinical
S. 10(1), 3-9.


Shahan, T. A., & Jimenez-Gomez, C. (2006). Effects of self-administered alcohol
concentration on the frequency and persistence of rats' attending to alcohol
cues. Behavioural ,. 17(3), 201-211.

Sharpe, A. L., & Samson, H. H. (2002). Repeated nicotine injections decrease
operant ethanol self-administration. Alcohol (Fayetteville, N.Y.), 28(1), 1-7.

Skinner, B. F. (1965). Science and Human Behavior. New York, NY: The Free
Press.

Steensland, P., Simms, J. A., Holgate, J., Richards, J. K., & Bartlett, S. E. (2007).
Varenicline, an alpha4beta2 nicotinic acetylcholine receptor partial agonist,
selectively decreases ethanol consumption and seeking. Proceedings of the
National Academy of Sciences of the United States of America, 1" -I-'i
12518-12523.

Warner, K. E., Hodgson, T. A., & Carroll, C. E. (1999). Medical costs of
smoking in the United States: Estimates, their validity, and their implications.
Tobacco Control, 8(3), 290-300.

Wyckoff, L. B. (1952). The role of observing-responses in discrimination
learning. .\ .',. '. .' Review, 59, 431-442.


University of Florida I Journal of Undergraduate Research I Volume 12, Issue 3 I Summer 2011
6




University of Florida Home Page
© 2004 - 2011 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated May 24, 2011 - Version 3.0.2 - mvs