Spontaneous orofacial dyskinesia and dopaminergic function in rats after 6 months of neuroleptic treatment.

A syndrome of spontaneous orofacial dyskinesia was identified in groups of rats treated for 6 months with a wide range of neuroleptic drugs. Phenothiazines, thioxanthenes, and substituted benzamides were particularly likely to induce the syndrome. It was observed in the presence of a functional blockade of dopamine receptors and endured for at least 2.5 months after drug withdrawal. There was no relation between the syndrome and changes in striatal dopamine receptors, as indexed by the binding of tritiated spiperone and tritiated cis(Z)-flupenthixol. The syndrome parallels several of the features of clinical tardive dyskinesia, whose pathophysiology thus may not involve changes in the characteristics of striatal dopamine receptors.