Operant Self‐Administration Models for Testing the Neuropharmacological Basis of Ethanol Consumption in Rats

Harry L. June1, Nicholas W. Gilpin2

1 University of Maryland School of Medicine, Baltimore, Maryland, 2 The Scripps Research Institute, La Jolla, California
Publication Name:  Current Protocols in Neuroscience
Unit Number:  Unit 9.12
DOI:  10.1002/0471142301.ns0912s51
Online Posting Date:  April, 2010
GO TO THE FULL TEXT: PDF or HTML at Wiley Online Library


Operant self‐administration procedures are used to assess the neural basis of ethanol‐seeking behavior under a wide range of experimental conditions. In general, rats do not spontaneously self‐administer ethanol in pharmacologically meaningful amounts. This unit provides a step‐by‐step guide for training rats to self‐administer quantities of ethanol that produce moderate to high blood‐alcohol content. Different protocols are used for rats that are genetically heterogeneous versus rats that are selectively bred for high alcohol preference. Also, these protocols have different sets of advantages and disadvantages in terms of the ability to control for caloric intake and taste of solutions in operant testing. Basic self‐administration protocols can also be altered to focus on different aspects of the motivational properties of ethanol (for example, those related to dependence). This unit provides multiple protocols that lead to alcohol intake in rats, which can be pharmacologically probed relative to a variety of control conditions. Curr. Protoc. Neurosci. 51:9.12.1‐9.12.26. © 2010 by John Wiley & Sons, Inc.

Keywords: ethanol; alcohol; self‐administration; neuropharmacology; operant learning

PDF or HTML at Wiley Online Library

Table of Contents

  • Introduction
  • Strategic Planning
  • Basic Protocol 1: Train Rats to Initiate Ethanol‐Maintained Responding on an FR‐4 Schedule
  • Support Protocol 1: Blood Alcohol Content (BAC)
  • Support Protocol 2: Training Rats to Respond for Ethanol on a Progressive‐Ratio Schedule
  • Support Protocol 3: Testing Ethanol Self‐Administration Behavior in Alcohol‐Dependent Rats
  • Basic Protocol 2: Train Rats to Initiate Saccharin‐Maintained Responding on an FR‐4 Schedule
  • Basic Protocol 3: Train Rats to Lever Press Concurrently for Ethanol and Saccharin Under an FR‐4 Schedule
  • Basic Protocol 4: Train Rats to Lever Press Concurrently for Alcohol and an Isocaloric Alternative Solution Under an FR‐4 Schedule
  • Basic Protocol 5: Train Rats to Initiate Binge‐Like Ethanol Responding in an Operant Situation
  • Commentary
  • Literature Cited
  • Figures
PDF or HTML at Wiley Online Library


Basic Protocol 1: Train Rats to Initiate Ethanol‐Maintained Responding on an FR‐4 Schedule

  • Ten 2‐ to 3‐month‐old naïve outbred rats or rats selectively bred for alcohol consumption (∼200 to 300 g, female or male)
  • Standard rodent diet
  • 0.10% (w/v) saccharin (Fisher Scientific) solution in distilled water
  • 2% (v/v) ethanol/0.075% (w/v) saccharin solution
  • 5% and 10% (v/v) ethanol solutions
  • Wire‐mesh stainless‐steel cages or plastic tubs
  • Personal computer with standard operant software packages (e.g., from Coulbourn Instruments or Med Associates) to record responses and control reinforcements
  • Stopwatch
  • Ten standard operant chambers (Coulbourn Instruments; Fig. A) equipped with two removable levers (Fig. B) and two dipper fluid delivery systems (Fig. C) enclosed in sound‐attenuated cubicles (Fig. D)
  • Animal balance for weighing rats
NOTE: Dipper presentations should provide 1.5‐sec access to a 0.10‐ml dipper solution, followed by a 3‐sec time‐out period; the amount of the earned reinforcer delivered following the various response requirements in Basic Protocols protocol 11 to protocol 74 is 0.10 ml. Above each lever, a stimulus light (red, green, or yellow) is present and is illuminated upon presentation of the stimulus delivery/reinforcer (Fig. B).

Support Protocol 1: Blood Alcohol Content (BAC)

  • Rats (see Basic Protocols protocol 11 to protocol 74)
  • Heparin‐coated microcentrifuge tubes
  • Microcentrifuge
  • Clinical analyzer (GL‐5 MicroStat, Analox Instruments)
  • Clark‐type amperometric oxygen electrode
  • Additional reagents and equipment for collecting blood from the rat's tail (Donovan and Brown, )
NOTE: Use alcohol reagent buffer solutions (pH 7.4) and alcohol oxidase enzymes provided by the manufacturer (Analox Instruments) in all samples tested.

Support Protocol 2: Training Rats to Respond for Ethanol on a Progressive‐Ratio Schedule

  • 10% (w/v) sucrose solution

Support Protocol 3: Testing Ethanol Self‐Administration Behavior in Alcohol‐Dependent Rats

  • Glucose‐saccharin (“Supersac”) solution: 3% glucose + 0.0125% saccharin in water
  • Sweetened alcohol: 10%(w/v) ethanol + 3% glucose + 0.0125% saccharin in water
PDF or HTML at Wiley Online Library



Literature Cited

Literature Cited
   Bell, R.L., Rodd, Z.A., Lumeng, L., Murphy, J.M., and McBride, W.J. 2006. The alcohol‐preferring P rat and animal models of excessive alcohol drinking. Addiction Biol. 11:270‐288.
   Carroll, M.E., Carmona, G., and May, S.A. 1991. Modifying drug‐reinforced behavior by altering the economic conditions of the drug and a non‐drug reinforcer. J. Exp. Anal. Behav. 18:361‐376.
   Donovan, J. and Brown, P. 2006. Blood collection. Curr. Protoc. Immunol. 73:1.7.1‐1.7.9.
   Gilpin, N.W., Richardson, H.N., Lumeng, L., and Koob, G.F. 2008. Dependence‐induced alcohol drinking by alcohol‐preferring (P) rats and outbred Wistar rats. Alcohol. Clin. Exp. Res. 32:1688‐1696.
   Herz, A. 1997. Endogenous opioid systems and alcohol addiction. Psychopharmacology 129:99‐111.
   Heyman, G.M. and Oldfather, C.M. 1992. Inelastic preference for ethanol in rats: An analysis of ethanol's reinforcing effects. Psychol. Sci. 3:122‐130.
   Hubbell, C.L. and Reid, L.D. 1990. Opioids modulate rat's intake of alcoholic beverages. In Opioids, Bulimia and Alcohol Abuse and Alcoholism (L.D. Reid, ed.) pp. 145‐191. Springer‐Verlag, New York.
   Hyytia, P. and Kiianmaa, K. 2000. Suppression of ethanol responding by centrally administered CTOP and naltrindole in AA and Wistar rats. Alcohol. Clin. Exp. Res. 25:25‐33.
   Ji, D., Gilpin, N.W., Richardson, H.N., Rivier, C.L., and Koob, G.F. 2008. Effects of naltrexone, duloxetine, and a corticotrophin‐releasing factor type 1 receptor antagonist on binge‐like alcohol drinking in rats. Behav. Pharmacol. 19:1‐12.
   June, H.L., Hughes, R.W., Spurlock, K.R., Domangue, K.R., and Lewis, M.L. 1994. Ethanol self‐administration in freely‐feeding rats: Effects of Ro15‐4513 alone, and in combination with flumazenil (Ro15‐1788). Psychopharmacology 115:332‐339.
   June, H.L., Grey, C., Warren‐Reese, C., Lawrence, A., Thomas, A., Cummings, R., Williams, L., McCane, S.L., Durr, L.F., and Mason, D. 1998a. The opioid receptor antagonist nalmefene reduces alcohol motivated behaviors: Preclinical studies in alcohol preferring (P) and outbred Wistar rats. Alcohol. Clin. Exp. Res. 22:2174‐2185.
   June, H.L., Torres, L., Cason, C.R., Hwang, B.H., Braun, M.R., and Murphy, J.M. 1998b. The novel benzodiazepine inverse agonist RO19‐4603 antagonizes ethanol motivated behaviors: Neuropharmacological studies. Brain Res. 784:256‐275.
   June, H.L., McCane, S., Zink, R.W., Portoghese, P., Li, T.K., and Froehlich, J.C. 1999. The delta 2‐opioid receptor antagonist naltriben reduces motivated responding for ethanol. Psychopharmacology 147:81‐89.
   June, H.L., Harvey, S.C., Foster, K.L., McKay, P.F., Cummings, R.C., Garcia, M., Mason, D., Grey, C., McCane, S., Williams, L., Johnson, T.B., He, X., Rock, S., and Cook, J.M. 2001. GABAA‐receptors containing α5 subunits in the CA1 and CA3 hippocampal fields regulate ethanol‐motivated behaviors: An extended ethanol reward circuitry. J. Neurosci. 21:2166‐2177.
   Lumeng, L., Murphy, J.M., McBride, W.J., and Li, T.‐K. 1995. Genetic influences on alcohol preference in animals. In The Genetics of Alcoholism (H. Begleiter and B. Kissin, eds.) pp. 165‐201. Oxford University Press, New York.
   Linseman, M.A. 1987. Alcohol consumption in freely feeding rats: Procedural, genetic and pharmacokinetic factors. Psychopharmacology 92:254‐261.
   McBride, W.J. and Li, T.‐K. 1998. Animal models of alcoholism: Neurobiology of high alcohol‐drinking behavior in rodents. Crit. Rev. Neurobiol. 12:339‐369.
   McCullough, D.E., Mosemiller, A.K., Zhou, F.C., Portoghese, P.S., and Froehlich, J.C. 1998. Infusion of a delta opioid antagonist into the ventral tegmental area attenuates alcohol drinking in P rats. Alcohol. Clin. Exp. Res. 22:45.
   Nowak, K.L., McBride, W.J., Lumeng, L., Li, T.‐K., and Murphy, J.M. 1998. Blocking GABAA receptors in the anterior ventral tegmental area attenuates ethanol intake of the alcohol‐preferring P rat. Psychopharmacology 139:108‐116.
   O'Dell, L.E., Roberts, A.J., Smith, R.T., and Koob, G.F. 2004. Enhanced alcohol self‐administration after intermittent versus continuous alcohol vapor exposure. Alcohol. Clin. Exp. Res. 28:1676‐1682.
   Petry, N.M. 1997. Benzodiazepine‐GABA modulation of concurrent ethanol and sucrose reinforcement in the rat. Exp. Clin. Psychopharmacol. 5:183‐194.
   Petry, N.M. and Heyman, G.M. 1995. Behavioral economic analysis of concurrent ethanol/sucrose and sucrose reinforcement in the rat: Effects of altering variable‐ratio requirements. J. Exp. Anal. Behav. 64:331‐359.
   Ragnauth, A., Ruegg, H., and Bodnar, R.J. 1997. Evaluation of opioid receptor subtype antagonist effects in the ventral tegmental area upon food intake under deprivation, glucoprivic and palatable conditions. Brain Res. 767:8‐16.
   Rodefer, J.S., Campbell, U.C., Cosgrove, K.P., and Carroll, M.E. 1999. Naltrexone pretreatment decreases the reinforcing efficacy of ethanol and saccharin but not PCP or food under concurrent progressive‐ratio schedules in rhesus monkeys. Psychopharmacology 147:81‐89.
   Samson, H.H. 1986. Initiation of ethanol reinforcement using a sucrose‐substitution procedure in food‐ and water‐sated rats. Alcohol. Clin. Exp. Res. 10:436‐442.
   Samson, H.H. 1987. Initiation of ethanol‐maintained behavior: A comparison of animal models and their implication to human drinking. In Neurobehavioral Pharmacology: Advances in Behavioral Pharmacology, Vol. 6 (T. Thompson, P.B. Dews, and J. Barret, eds.) pp. 221‐248. Lawrence Erlbaum Associates, Philadelphia.
   Samson, H.H. and Grant, K.A. 1985. Chlordiazepoxide effects on ethanol self‐administration: Dependence on concurrent conditions. J. Exp. Anal. Behav. 43:353‐364.
   Samson, H.H. and Hodge, C.W. 1996. Neurobehavioral regulation of ethanol intake. In Pharmacological Effects of Ethanol on the Nervous Systems (R.A. Deitrich and V.G. Erwin, eds.). pp. 203‐226. CRC Press, New York.
   Samson, H.H., Haraguchi, M., Tolliver, G.A., and Sadeghi, K.G. 1989. Antagonism of ethanol‐reinforced behavior by the benzodiazepine inverse agonists RO15‐4513 and FG 7142: Relationship to sucrose reinforcement. Pharm. Biochem. Behav. 33:601‐608.
   Stratford, T.R. and Kelley, A.E. 1997. GABA in the nucleus accumbens shell participates in the central regulation of feeding. J. Neurosci. 17:4434‐4440.
   Walker, B.W. and Koob, G.F. 2007. The gamma‐aminobutyric acid‐B receptor agonist baclofen attenuates responding for ethanol in ethanol‐dependent rats. Alcohol Clin. Exp. Res. 31: 11‐18.
   Weiss, F. and Koob, G.F. 1991. The neuropharmacology of ethanol self‐administration. In Neuropharmacology of Ethanol (R.F. Meyer, G.F. Koob, M.J. Lewis, and S. Paul, eds.) pp. 125‐162. Birkhauser, Boston.
PDF or HTML at Wiley Online Library