MK-771 antagonizes the enhanced response to apomorphine in rats treated chronically with haloperidol - implications...

Rats that have been chronically exposed to neuroleptic drugs exhibit an enhanced stereotypic response to dopaminergic agonists, and it has been suggested that this phenomenon is a useful animal model of tardive dyskinesia. Administration of MK-771, a well characterized analog of thyrotropin releasing hormone (TRH), has been found to attenuate the enhanced response to apomorphine in rats chronically treated with haloperidol. This finding is discussed in light of similar observations with choline and physostigmine and the established cholinergic stimulating properties of MK-771 and TRH. It is suggested that peptides of this nature may represent novel and useful agents to ameliorate the symptoms of tardive dyskinesia.