Effects of amphetamine on C-fos expression and calbindin-D(28K) expression in the rat dorsal striatum and associated amphetamine-induced behaviors: Sex differences and hormonal influences.

Abstract

There are sex differences and hormonal influences on amphetamine (AMPH)-induced striatal dopamine (DA) release and AMPH-induced behavior. There are also sex differences and hormonal effects on DA uptake, DA receptor binding sites and DA metabolism in the striatum. Thus, it is possible that there are sex differences in the underlying anatomical organization of the striatum. The present series of experiments were designed to: (1) characterize the distribution of Fos- and calbindin-positive neurons within circumscribed regions of the dorsal striatum of the intact male rat across different rostrocaudal levels using quantitative analysis of immunohistochemical material; (2) examine possible sex differences and hormonal influences on AMPH-induced Fos expression and calbindin expression across regions and rostrocaudal levels of the dorsal striatum of intact and gonadectomized male and female rats; and (3) characterize sex differences and hormonal influences on AMPH-induced behavior using newly developed quantitative measures of AMPH-induced behavior. In the male rat dorsal striatum, AMPH-induced Fos expression was heterogeneously and sparsely distributed within striatal subregions and across different rostrocaudal levels. Furthermore, there was an effect of sex and hormonal condition on AMPH-induced Fos expression in the dorsal striatum. Females in proestrus had a greater percent of Fos-expressing neurons in the middle and caudal dorsolateral striatal regions and in the caudal ventrolateral striatal region compared to diestrous, ovariectomized female, castrated male and intact male rats. There was no effect of sex, hormonal condition or a single injection of AMPH on the number of calbindin-immunoreactive neurons across different rostrocaudal levels of the dorsal striatum. There were, however, sex differences and hormonal influences on AMPH-induced behavior. Intact females showed a greater behavioral response to AMPH compared to intact males across all quantitative behavioral measures.