Effects of Estrogen and Progesterone as Revealed by Neurophysiological Methods

Abstract

The dependence of reproductive behavior on sex steroids has been well documented and reviewed for several mammalian species (Beach 1948; Baum 1979; Pfaff 1980). Since behavior in general is a final product of integrative action of the central nervous system, the example of reproductive behavior signifies that sex steroids act on the neural tissue at some level. Also compelling is the evidence of the feedback action of sex steroids and glucocorticoids, which has been shown to be mediated by limbic and hypothalamic structures (Harris 1955; Mangili et al. 1966). Steroid hormones exert their effects on the central nervous system partly through a genomic mechanism which can be blocked by inhibitors of DNA-dependent RNA synthesis or protein synthesis (McEwen et al. 1979). New protein synthesis as a result of the genomic action of steroids has been clearly defined for peripheral target tissues, as, for example, in the action of estrogen in the uterus (O’Malley and Means 1974). Evidence that steroids are incorporated into central neurons includes early demonstration by autoradiography of estrogen, progesterone, and testosterone in the hypothalamus (Pfaff and Keiner 1973; Stumpf and Sar 1976; Sar and Stumpf 1973) and glucocorticoids in the hippocampus (Warembourg 1975). Biochemical studies have shown that these structures contain specific cytosolic and nuclear receptors for estrogen (Zigmond and McEwen 1970), progesterone (Kato and Onouchi 1977), and Cortisol (Chytil and Toft 1972). Estrogenic induction of various enzyme activities and of structural protein synthesis, as measured by incorporation of amino acids, is attributed to this type of receptor mechanism.