Effect of naloxone on appetitive and consummatory phases of ethanol self-administration.
BACKGROUND
The opioid system has been implicated in ethanol self-administration. Morphine, an opiate agonist, can sometimes increase the amount of ethanol consumed, and opiate antagonists such as naloxone and naltrexone decrease the amount of ethanol consumed in both animals and humans. The objective of this study was to examine the effect of naloxone on appetitive (or seeking) and consummatory behaviors by using an operant model developed to separate these two phases of self-administration.


METHODS
Intraperitoneal injections of naloxone (0.3-10 mg/kg) or vehicle were given before operant self-administration sessions to assess the effect on lever pressing (appetitive behavior) and subsequent consumption. Effects were measured in two groups of rats: one self-administered a 3% sucrose solution and the other a 10% ethanol solution.


RESULTS
Naloxone dose-dependently decreased ethanol and sucrose consumption by an earlier cessation of drinking in the session compared with vehicle injection days. There were some effects on appetitive responding after treatment with naloxone, but none was statistically significant.


CONCLUSIONS
Naloxone may decrease ethanol self-administration by decreasing the postingestive or pharmacological effects of alcohol. This model provides a new method for examining the effects of potential pharmacotherapeutics on alcohol self-administration behavior.
Sharpe
A L
AL
Department of Physiology and Pharmacology, Center for the Neurobehavioral Study of Alcohol, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1083, USA. asharpe@wfubmc.edu
Samson
H H
HH
D000428:Alcohol Drinking / Q000523:psychology*; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003259:Consummatory Behavior / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D051381:Rats; D020318:Rats, Long-Evans; D013395:Sucrose / Q000494:pharmacology
D009292:Narcotic Antagonists; D009270:Naloxone; D013395:Sucrose