Dopamine-mediated behaviors: characteristics of modulation by estrogen

Several behaviors produced by intrastriatal injection of dopamine (DA) and amphetamine (AMPHET) in ovariectomized (OVX) rats were each modulated by estradiol benzoate (EB) in different ways. Contralateral postural deviation and rotation, induced by unilateral injections of DA and AMPHET into the dorsal striatum, were differentially suppressed with EB treatment. Postural deviation was suppressed by 1/2 hour after a single treatment with EB (2 micrograms). In contrast, suppression of contralateral rotation required two treatments with EB separated by an interval of 48 or 96 hours, and the suppression was observed at 24 hours after the last treatment with EB. However, treatment with the antiestrogen CI-628 blocked the suppressive effects of EB on either behavior. The enhanced locomotion produced by bilateral injections of AMPHET into the ventral striatum was not suppressed with EB. In fact, AMPHET-enhanced locomotor activity decreased after a 3-week absence of estradiol as a consequence of OVX, and was returned to early OVX levels by EB. Therefore, postural deviation, rotation, and locomotor activity are mediated by different underlying mechanisms in the striatum and are affected differently by estradiol.