Oral dyskinesia in brain-damaged rats withdrawn from a neuroleptic: Implication for models of tardive dyskinesia

Rats with ablated frontal sensorimotor cortex and one with ablated sensorimotor connections to forebrain showed more vacuous chewing movements following 6-week chronic administration of a neuroleptic than did occipitally damaged rats or normal controls who were treated in the same way. The effect was still present 1 month after withdrawal. It was not clearly enhanced by subsequent treatments. Other behaviors (e.g., walking, rearing, or grooming) were not similarly affected by drug withdrawal. Additional results of terminal probes with amphetamine, apomorphine, and haloperidol are described, including movements labeled sham eating, observed only in frontal rats given apomorphine (AP). The results are interpreted in terms of a Jacksonian model of levels of brain organization; such a model may be applicable to tardive dyskinesia, seen in many schizophrenic patients who are maintained on neuroleptics for long periods.