Estradiol suppresses then enhances intracaudate dopamine-induced contralateral deviation

The effects of estradiol on the amount of contralateral postural deviation elicited by unilateral intracaudate injection of dopamine (DA) were tested 2 days and 6 days after hormone treatment. DA (25 micrograms/0.25 microliter) or a control vehicle solution (VH, 0.25 microliter) was injected unilaterally into the dorsal anterior caudate-putamen of intact male rats and postural deviation was measured. Then, rats were given estradiol benzoate (EB, 50 micrograms/100 g body wt per 0.05 ml) or the vehicle, peanut oil (OIL, 0.05 ml/100 g body wt) once. At 2 days and 6 days after EB or OIL treatment, the rats were again administered DA or VH intrastriatally and the amount of contralateral postural deviation was measured. At 2 days after EB treatment the response to intrastriatal DA was significantly decreased, but by 6 days it was significantly increased; OIL had no effect. Thus, the behavioral effects of estrogen are time-dependent and may affect the postsynaptic response to DA in the striatum.