Responding for oral ethanol after naloxone treatment by alcohol-preferring AA rats.
The present study examined the effect of a relatively nonselective opioid antagonist, naloxone, on lever pressing for oral ethanol by the alcohol-preferring AA rats. The AAs, housed continually in operant chambers with free access to food and water, learned to respond for 10% oral ethanol during daily 60-min alcohol access periods indicated by a stimulus light. The rats developed stable ethanol responding, resulting in mean ethanol intakes of 1.2 g/kg/60 min and measurable blood alcohol levels. In the first experiment, single systemic injections of naloxone (0.05-2.5 mg/kg) had no effect on the initial rate of responding; dose-dependent decreases were observed later during the alcohol access. The second experiment examined the effects of repeated injections of 0.5 and 2.5 mg/kg naloxone on 5 consecutive days. Naloxone suppressed responding dose-relatedly over the treatment days. In contrast to the effects of single injections, repeated injections with 2.5 mg/kg naloxone produced progressive decreases within the first minutes of access. The results suggest that naloxone may attenuate the reinforcing actions of ethanol.
Hyytiä
P
P
Biomedical Research Center, Alko Ltd., Helsinki, Finland.
Sinclair
J D
JD
D000428:Alcohol Drinking / Q000503:physiopathology*; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000502:physiology*; D007031:Hypothalamus / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000187:drug effects / Q000502:physiology*
D004723:Endorphins; D011957:Receptors, Opioid; D009270:Naloxone