Neuroleptic suppression of feeding and oral stereotypy following microinjections of carbachol into substantia nigra.

A large dose of carbachol (5 micrograms/0.5 microliters) unilaterally microinjected into the rostral substantia nigra of rats induced stereotypy characterized by biting, gnawing and licking. A lower dose (0.5 micrograms/0.5 microliter) of the cholinomimetic potentiated normal food intake in satiated animals. Both the cholinergically induced feeding and stereotypy were severely attenuated by subcutaneous administration of haloperidol 0.4 mg/kg. This particular dose of neuroleptic had no significant effect on locomotor activity. These data are consistent with the hypothesis that cholinergic neurotransmission in the rostral substantia nigra mediating oral responses is afferent to the dopamine systems arising from this area.