Dopaminergic nature of amphetamine-induced pecking in pigeons.

d-Amphetamine was found to induce a pecking response in pigeons. The pecking response induced by d-amphetamine was antagonized by chlorpromazine, haloperidol or bulbocapnine indicating that this pecking response was caused by dopaminergic receptor stimulation. Pretreatment of pigeons with alpha-methyltyrosine (alpha-MT) reduced d-amphetamine-induced pecking, while the combined treatment of pigeons with alpha-MT and L-dihydroxyphenylalanine (L-DOPA, 100 mg/kg) partially restored the pecking response. d-Amphetamine-induced pecking was not reduced by a dopamine-beta-hydroxylase inhibitor, 1-phenyl-3-(2-thiazolyl)-2-thiourea (U-14,624). Alpha-MT reduced brain dopamine but not norepinephrine level, whereas U-14,624 decreased brain norepinephrine but not dopamine. Thus there is a correlation between brain dopamine level and d-amphetamine-induced pecking response. It is concluded that d-amphetamine-induced pecking is mediated indirectly by the release of dopamine.