Effects of neurohypophyseal hormones on food-reinforced classical conditioning in the rat.
The effects of different doses of lysine vasopressin (LVP) and oxytocin (OXT) were studied on the six-day acquisition or extinction of a food-reinforced classical conditioning reflex (conditional stimulus: light) when intraperitoneal (ip.) injections were carried out 20 min prior to the behavioural sessions. The highest (600 mU/kg) dose of LVP inhibited acquisition, and all LVP doses tested (150, 300 and 600 mU/kg) facilitated the extinction of conditioned behaviour. These same mU doses of OXT did not significantly affect the food-reinforced conditioning, although a consequent tendency towards increased performance (the opposite action to vasopressin) was observed. When 2.5 or 25 micrograms/kg doses of desglycinamide-arginine-vasopressin (DGAVP), a 500 micrograms/kg dose of prolyl-leucyl-glycinamide (PLG) or a 1200 mU/kg dose of OXT was injected during the extinction sessions, 2.5 micrograms/kg DGAVP and 1200 mU/kg OXT significantly facilitated extinction; the other treatments were without effect. LVP in a dose of 300 or 600 mU/kg and OXT in a dose of 300, 600 or 1200 mU/kg did not influence the food intake of 22 h food-deprived rats in a nonconditional situation. The present results indicate that the effects of LVP and OXT on memory display reinforcement-dependent characteristics, and are thus indirect or non-specific in nature.
D000818:Animals; D003214:Conditioning, Classical / Q000187:drug effects*; D004435:Eating / Q000187:drug effects*; D005508:Food Deprivation; D008236:Lypressin / Q000031:analogs & derivatives / Q000494:pharmacology*; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology; D008297:Male; D010121:Oxytocin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012054:Reinforcement, Psychology
C000879:vasopressin, 9-des-Gly-NH(2)-Lys-; D010121:Oxytocin; D008236:Lypressin; D009075:MSH Release-Inhibiting Hormone