The effects of estrogen on apomorphine-induced hypothermia and stereotypy in the rat.

ABSTRACT

The effects of various doses of estrogen on apomorphine (Apo)-induced hypothermia and stereotypy were investigated in ovariectomized rats. Daily administration of estradiol (5, 15 or 100 micrograms/kg) for 4 days or estradiol (100 micrograms/kg) for 3 days, followed by 4 and 72 hr withdrawal periods respectively, had no effect on apomorphine-induced hypothermia or stereotypy in a cold (4 degrees C) environment, although both effects were blocked by haloperidol. Large doses of estradiol (100 micrograms/kg) given for 3 days, followed by either 24 or 72 hr withdrawal, slightly attenuated apomorphine-induced stereotypy at 22 degrees C. Stereotypy observed at 22 degrees C was of greater magnitude than that seen at 4 degrees C. The results indicate that although high, non-physiological levels of estrogen may attenuate striatal-dependent stereotypies, this hormone has no detectable influence on dopaminergic mechanisms in the preoptic-anterior hypothalamic regions that are thought to mediate apomorphine-induced hypothermia.