Ligand-independent activation of progestin receptors: relevance for female sexual behaviour

Abstract

is, by ligand-or steroid-independent activation. More importantly, ligand-independent activation of steroid receptors (that is, progestin receptors) within the brain can influence reproductive behaviour in rodents. This review focuses on recent findings which indicate that some somatosensory cues normally experienced by females, such as those associated with sexual contact with males, can activate progestin receptors to influence both neuronal response and oestrous behaviour in a ligand-independent manner. Hormonal requirements for the induction of sexual behaviourDuring the oestrous cycle in rats, sexual behaviour is dependent upon an increase in serum oestradiol followed by an increase in progesterone concentrations. Sexual behaviour is abolished by ovariectomy, and reinstated by the injection of oestradiol followed 1 or 2 days later by progesterone. Treatment with oestradiol alone can induce some aspects of sexual behaviour, such as receptivity (for example, lordosis); however, oestradiol followed by progesterone administration induces the full complement of proceptive behaviours that occur during normal oestrus, such as ear wiggling, hopping and darting behaviour (Blaustein and Olster, 1989). This finding indicates that both oestradiol and progesterone are critical for the occurrence of normal oestrous behaviour. Oestradiol and progesterone are secreted from both the ovaries and the adrenal glands (Shaikh and Shaikh, 1975). Steroid hormone secretion from the adrenal glands appears to be important for the normal timing of sexual behaviour in rats, as stress resulting from sham ovariectomy advances, and stress resulting from adrenalectomy delays, the onset of oestrous behaviour. In addition, the small increase in solicitational behaviour induced by oestradiol treatment alone is blocked by adrenalectomy. Therefore, sexual behaviour is influenced by secretion of steroid hormones not only from the ovary, but also from the adrenal glands. Behavioural and physiological changes associated with mating stimulationWhen mating occurs, the female rat experiences a variety of somatosensory and olfactory stimuli from the male that further influences female sexual behaviour (Pfaff et al., 1994). For example, ovariectomized rats primed with low doses of oestradiol exhibit reduced lordosis in the presence of a sexually active male; however, repeated exposure of ovariectomized oestradiol-primed female rats to males will induce increased lordosis (Hardy and Debold, 1973). The increase in lordosis owing to repeated mating of oestradiolprimed female rats occurs within an hour, and this behavioural phenomenon is not dependent upon the adrenal glands (Foreman and Moss, 1977). Therefore, mating-related stimuli increase sexual receptivity in the absence of circulating progesterone. It is not clear which somatosensory and olfactory cues are important for mediat-

Sex Differences in Fos Protein Expression in the Neonatal Rat Brain

“…Although steroid hormones are the most likely candidates for steroid receptor activation, other factors may play a role as well. For example, steroid hormone receptors can also be activated in the absence of steroid hormones by the neurotransmitter dopamine (66) or through social interaction (67, 68). Therefore, it is possible to have other factors besides steroid hormones that act upon steroid receptors to influence Fos expression in a sexually dimorphic manner.…”

Methamphetamine facilitates female sexual behavior and enhances neuronal activation in the medial amygdala and ventromedial nucleus of the hypothalamus

“…The neurotransmitter dopamine is an important modulator of many motivated behaviors, including the motivation to seek out sexual partners (Auger, 2001; Becker et al, 2001). Recent evidence suggests that the mesolimbic dopamine system mediates the motivation or the ‘wanting’ of a natural and/or hedonic stimulus by attributing salience to it, as opposed to mediating the pleasure or ‘liking’ of a reward (Ikemoto and Panksepp, 1999; Berridge, 2007; Salamone et al, 2007).…”

Variations in maternal care alter corticosterone and 17beta-estradiol levels, estrous cycle and folliculogenesis and stimulate the expression of estrogen receptors alpha and beta in the ovaries of UCh rats

“…Ovarian steroid hormones, such as estradiol (E2), strongly influence neural circuits that regulate sexual behavior and estrous cycle [18]. The action of E2 and androgens is mediated through estrogen receptors (ER), composed of ER-α and ER-β subunits, and androgen receptors (AR), respectively.…”