Infusion of gamma 2-MSH produce a conditioned taste aversion in morphine-dependent rats.
A two flavour, unbiased, taste preference conditioning procedure was used to test for possible motivating effects of gamma 2-MSH. Three training trials failed to produce any significant effect with doses ranging from 2.4 to 40 micrograms/ICV infusion in drug-naive, non-operated or placebo-implanted rats. However, in rats made dependent by SC implantation of a morphine pellet 4 days earlier 15 micrograms gamma 2-MSH/infusion produced a taste aversion that was comparable to that produced by infusion of a low dose of the competitive opioid receptor antagonist naloxone (0.32 micrograms). The findings confirm with a conditioning procedure and with opiate-dependent animals the naloxone-like effects of gamma 2-MSH. They also suggest that this endogenously-located peptide may acquire an aversive property as a result of chronic morphine treatment.
Mucha
R F
RF
Biobehavioral Research Department, Addiction Research Foundation, Toronto, Ontario, Canada.
van Ree
J M
JM
D000818:Animals; D003213:Conditioning, Psychological / Q000187:drug effects*; D005518:Food Preferences / Q000187:drug effects*; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D009021:Morphine Dependence / Q000523:psychology*; D009042:Motivation / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013649:Taste
D009270:Naloxone; D009074:Melanocyte-Stimulating Hormones