Possible mechanisms involved in the stereotyped behavior elicited by amphetamine.

In a variety of animals, amphetamine administration produces an increase in locomotor behavior and an induction of repetitive, stereotyped behaviors. There is now considerable evidence to suggest that the induction of stereotyped behaviors is accomplished, in part, by alterations in catecholaminergic transmission in the central nervous system. By recording the spontaneous activity of neurons in the rat brain substantia nigra, reticular formation, basal ganglia, and elsewhere during systemic administration of amphetamine and related drugs, or during administration by means of microinfusions directly into these brain regions, relationships may be drawn between the biochemical and behavioral effects of these drugs and drug-induced changes in neuronal activity in the central nerovous system. Current evidence, for example, suggests that amphetamine produces an inhibition of neuronal activity in the neostriatum and pars compacta of the substantia nigra by means of dopamine released from dopaminergic terminals in the neostriatum and dopaminergic dendrites in the substantia nigra respectively. In addition, current evidence suggests the possibility of a GABA-mediated functional antagonism between excitatory cortical and/or thalamic input to the neostriatum and dopaminergic input from the substantia nigra which could be involved in the apparently mutually exclusive occurrence of amphetamine-induced locomotion and stereotyped behaviors that follow amphetamine administration. Such evidence may also have relevance to a variety of behavioral disorders involving the basal ganglia and catecholaminergic transmission in the central nervous system.