Effect of estradiol and haloperidol on hypophysectomized rat brain dopamine receptors

The effect of chronic haloperidol and estradiol treatments on dopamine receptors independent from the pituitary has been studied in ovariectomized (ovx) and hypophysectomized (hypox) rats. The striatal dopamine receptor density (Bmax) of hypox rats as measured with [3H]spiperone binding was increased after chronic estradiol or haloperidol treatment, while receptor affinity was unchanged. In hypox rats, estradiol given during withdrawal from haloperidol decreased the characteristic increase in dopamine receptor density observed upon withdrawal from this neuroleptic, while the estrogen was ineffective when given concomitantly with haloperidol. These results in hypox rats are similar to those observed in ovx rats, suggesting that haloperidol and estradiol influence striatal dopamine function independently of the pituitary.