Pharmacologic manipulations of brain catecholamines and the behavior of Callithrix jacchus (marmoset)

In experiment 1, groups of marmosets were injected with 50 - 200 mg/kg L-dopa, 0.5 - 2.0 mg/kg apomorphine (AP), or 0.5 - 5.0 mg/kg methamphetamine. The number of head movements, number of body movements, number of times the tongue was extended, and the time the animal remained in an upright posture were scored during a 90-min period after the injections. L-Dopa and AP induced large dose-dependent increases in body movements and time in upright posture. Furthermore, the smallest dose of AP induced self-destructive behavior. The main effect produced by methamphetamine was a constant turning of the head with the body remaining still. In experiment 2, the marmosets were treated with alpha-methyl-p-tyrosine (AMPT) or haloperidol prior to challenge with AP or methamphetamine. Haloperidol blocked most of the effects of both drugs, while AMPT blocked only methamphetamine effects. In experiment 3, marmosets were injected with increasing doses of haloperidol for 22 days. Upon withdrawal of the neuroleptic, methamphetamine and AP effects were not increased, suggesting absence of supersensitivity of dopaminergic receptors.