Effects of sex steroids on muscarinic sties in the rat brain

The level of binding sites for [3H]scopolamine in the rat hypothalamus and amygdala (but not elsewhere in the brain) is modified by hormonal status. In females, there is an inverse relation between the level of sites and estrogen (E2) and progesterone (P) concentration. Binding is high in metoestrous (Met) and in ovariectomized (Ovx) animals but low in proestrous (Pro). Hormone replacement in ovariectomized animals lowers the level of the sites. Castration (Cast) of males reduces the level of sites but subsequent testosterone (T) treatment restores normal levels. The results support a role of hormones in sexual behavior via alteration in levels of muscarinic receptors: male hormone increases and female hormones decrease receptor levels