Cholinergic manipulation of perioral behaviour induced by chronic neuroleptic administration to rats

Rats treated continuously for 4 months with haloperidol (1.4-1.6 mg/kg/day), trifluoperazine (4.5-5.1 mg/kg/day), or sulpiride (102-110 mg/kg/day), but not clozapine (23-26 mg/kg/day), exhibited an increased frequency of chewing jaw movements. Chewing in both control and haloperidol-treated rats was increased by acute administration of the cholinergic agents pilocarpine or physostigmine. Physostigmine or pilocarpine also induced abnormal gaping jaw movements; physostigmine-induced gaping was more prevalent in haloperidol-treated rats than control rats receiving physostigmine alone. Acute administration of the anticholinergic agents scopolamine and atropine decreased chewing in control animals and reduced haloperidol-induced chewing to control values or below. The effects of these cholinergic manipulations suggest that neuroleptic-induced perioral responses in rats do not resemble tardive dyskinesia in man.