[Neurophysiologic and pharmacologic evidence of autoregulationin the nigrostriatal system].

Repeated electrical stimulation of substantia nigra in cats produces a progressive relaxation of the poststimulation stereotyped behavior. This effect may be consequent on the development of autoinhibition in the nigro-striatal pathways since the rate of stereotypy inhibition increases in the presence of low doses of amphetamine and apomorphine but is reduced by little doses of haloperidol. A possible reason for autoinhibition is likely to involve an activation of the presynaptic dopaminergic receptors on nigro-striatal axons.