Stimulation of Female Sex Behavior in Adrenalectomized Rats with Estrogen Alone

Abstract

Apparently normal sex behavior was produced in spayed rats by daily injections of 0.8 or 3.2 /*g estradiol benzoate. Adrenalectomy had no deleterious effect on this behavior. Uterine weight data suggested that the lower dose produced circulating estrogen levels within or below those occurring in physiological conditions. Since, in the combined ovariectomized-adrenalectomized females, all known sources of steroid hormones were removed, it is concluded that the expression of sexual receptivity in female rats does not require the presence of progesterone or adrenal androgens. (Endocrinology 82: 193, 1968) I T IS generally assumed that the expression of sexual behavior in the female rat depends upon adequate secretion of both estrogenic and progestational hormones by the ovary (1). To produce experimentally the characteristic lordosis response denoting sexual receptivity, most investigators use a regimen of 1 or 2 injections of an estrogen, followed by a larger quantity of progesterone about 6 hr before testing. While it is known that administration of large doses of estrogen alone can elicit this response (2), it has been suggested that the behavior of these animals is not normal (2), or that under such circumstances progesterone was supplied by the adrenal cortex (3). The fact that estrogen stimulates adrenocortical activity in the rat (4-6) lends some credence to the latter notion. Since ovariectomy or menopause does not seem to reduce sexual desire in women, it has been proposed that the hormonal determinants of their sexual behavior are of adrenocortical rather than ovarian origin (7). It was, therefore, of interest to determine whether the induction of sexual behavior in ovariectomized female rats by relatively low doses of estrogen was affected by the presence of the adrenal glands. Materials and MethodsFifteen 60-day-old female Long-Evans rats were ovariectomized and 19 others were simultaneously ovariectomized and adrenalectomized. Seven others Received July 5, 1967. This work was supported by USPHS Grant HD 00778.1 USPHS postdoctoral fellow. 2 USPHS predoctoral fellow.of similar age were not operated. The adrenalectomized rats received 0.9 % NaCl in their drinking bottles, but no corticosteroid replacement. Three weeks postoperatively, approximately half of the animals in each operated group received either 0.8 or 3.2 ng of estradiol benzoate in daily subcutaneous injections. Behavioral tests were conducted on days 1, 2, 3, 4, 5, 8, 10 and 12 following the onset of injections. The unoperated rats were not injected but were tested behaviorally at different stages of the estrous cycle. Illumination was supplied from 12 PM to 12 AM and behavioral tests were commenced at approximately 2 PM. Females were placed in semicircular testing cages with sexually experienced males. Each female received a minimum of 10 mounts, and all mounts by the male and lordoses by the female were recorded. Two observers were present during all testing sessions. On the day of the last test, all animals were autopsied, the complete...

Rethinking progesterone regulation of female reproductive cyclicity

“…1), in the gonadally intact state, some females allowed males to mount, exhibiting enough elements of sexual receptivity to permit vaginal deposition of sperm by the male (Movie S2). Such observations are consistent with previous reports showing estrogen alone can facilitate sexual behavior in the rat (21,22). The mating never yielded a pregnancy or pseudopregnancy; instead, Pgr Δ136E1 null female rats continued to cycle.…”

Gonadal steroid hormone modulation of nociception, morphine antinociception and reproductive indices in male and female rats

“…As expected, E2, E2 + P4, and T, but not P4 alone, also increased reproductive behavior and uterine weight, although to varying extents. As shown previously in studies of reproductive behavior, E2 by itself almost fully restored lordosis behavior and uterine weight to that observed in sham-estrus females, and P4 by itself had no effect on lordosis (Davidson et al, 1968;Young, 1961). In contrast, T only partially restored lordosis, and slightly, but not significantly, increased uterine weight above that in GDX control females.…”

“…Surgery (gonadectomy or sham-gonadectomy) was performed in rats that were approximately 3 months old. In all rats except sham females, basal nociception and morphine antinociception were tested 28 days after surgery, when endogenous hormone levels and associated reproductive behaviors have been shown to be minimal in GDX rats (Young, 1961;Davidson, 1966;Davidson et al, 1968;Damassa et al, 1977). Sham females were tested between 21 and 35 days post-surgery so that females in diestrus, proestrus and estrus could be identified and tested in approximately equal numbers.…”

“…Thus, gonadectomy-nociceptive test interval and steroid replacement regimens were chosen based on their documented ability to modify endogenous steroid levels and associated reproductive behavior and physiology of adult male and female rats (Young, 1961;Davidson, 1966;Davidson et al, 1968;Damassa et al, 1977). Because gonadal steroids fluctuate in gonadally intact female rats, we employed two strategies for examining the modulatory effects of gonadal steroids in females.…”

Temporal Coincidence between the Excitation of Ventromedial Hypothalamic Efferents and the Induction of Lordosis Reflex in Ovariectomized Estrogen-Primed Rats.

“…In ovariectomized animals, however, estrogen alone elicits the lordosis reflex, a major receptive component of female rat sexual behavior, provided that estrogen is given in large doses for a prolonged period [2][3][4]. Although certain estrogen actions depend on cross-talk between estrogen-and progestin-receptor signaling pathways [5], experiments that employed progestinreceptor blocker [6], antisense oligonucleotides to progestin receptor [7] or progestin-receptor knockout mice [8] showed that progestin receptors are not involved in the estrogen-induced Lordosis reflex.…”