Estrogen in experimental tardive dyskinesia.

Postmenopausal women have the highest incidence of tardive dyskinesia, suggesting that loss of ovarian function may predispose to this condition. Moreover, reports have indicated that estrogens could reduce abnormal movements in tardive dyskinesia. To test the effects of estrogen in tardive dyskinesia, ovariectomized rats were treated daily for 16 days with haloperidol alone (0.5 mg per kilogram) or haloperidol plus estradiol benzoate (EB; 8 microgram per kilogram). Rats were then challenged with apomorphine (0.25 mg per kilogram) 4 and 10 days after cessation of the chronic treatments. Chronic treatment with haloperidol alone enhanced the response to apomorphine, whereas the combined treatment produced a synergistic response. Rats treated chronically with haloperidol and then treated daily with EB after the haloperidol treatment showed an attenuation of drug-induced stereotypy. These data indicate that estrogen may mask development of tardive dyskinesia.