Effects of d-amphetamine and naloxone on brain stimulation reward.
Self-stimulation thresholds were determined in rats by means of a modification of the psychophysical method of limits. Reinforcement values were determined after the administration of d-amphetamine alone, naloxone alone, and naloxone administered concurrently with d-amphetamine. d-Amphetamine yielded dose-related decreases in the threshold (0.25--2.00 mg/kg IP), while naloxone alone (2.0--16 mg/kg IP) caused no consistent changes. For each animal, a dose of d-amphetamine that substantially lowered the threshold was then selected to be administered with varying doses of naloxone. The threshold-lowering effect of d-amphetamine was blocked by naloxone at doses as low as 2.0 or 4.0 mg/kg. This finding suggests the possible involvement of an opiate receptor in the mediation of the enhancement by d-amphetamine of brain stimulation reward.
D000818:Animals; D003913:Dextroamphetamine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004056:Differential Threshold; D004305:Dose-Response Relationship, Drug; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D051381:Rats; D012653:Self Stimulation / Q000187:drug effects*
D009270:Naloxone; D003913:Dextroamphetamine