A model for oral dyskinesia in rats.

Rats subjected to bifrontal cortical ablations developed vacuous chewing movements and jaw tremors that began 22 weeks after surgery, reached a peak rate of 4 to 8 per minute, and remained stable for an 8-week observation period. Chronic haloperidol administration to rats with bifrontal cortical ablations produced 15 to 20 movements per minute that persisted for 7 weeks after drug withdrawal. Drugs given to decrease dopaminergic, cholinergic, and gamma-aminobutyric acid (GABA)-ergic neurotransmission suppressed the movements, whereas cholinergic agonists increased them. This model of oral dyskinesia in rats may be useful in developing drugs for the treatment of facial dyskinesias in humans.