Effects of food deprivation on induction of neural progestin receptors by estradiol in Syrian hamsters

Abstract

-Food deprivation, as well as treatment with metabolic inhibitors, suppresses steroid hormone-induced estrous behavior in ovariectomized (OVX) Syrian hamsters. Previous work indicates that 48 h of food deprivation decreases the number of detectable estrogen-receptor immunoreactive (ERIR) cells in the ventromedial hypothalamus (VMH) and the area just lateral to it (VLH), increases the number of ERIR cells in the medial preoptic area (MPO), and has no effect on the number of ERIR cells in the nucleus of the solitary tract in OVX hamsters. The present study examined the effects of food deprivation on neural progestin receptor binding using an in vitro binding assay and on progestin receptor immunoreactivity (PRIR) in estradiol-primed, OVX hamsters. Parallel behavior tests for sexual behavior were also performed in both experiments. OVX hamsters received 2.5 µg estradiol benzoate (EB) and were fed ad libitum or food deprived at the same time. Forty-eight h later, animals were killed in preparation for the immunocytochemistry or progestin receptor assay. Binding assays indicated that 48 h food deprivation decreased progestin receptor levels in the preoptic area and had no effect in the mediobasal hypothalamus, an area which includes the VMH and the arcuate nucleus (ARH). Immunocytochemical analysis confirmed these findings. Food deprivation caused a decrease in sexual receptivity and in the number of detectable PRIR cells in the MPO and medial amygdala but had no effect on the number of detectable PRIR cells in the VMH/VLH, the ARH, or the anteroventral periventricular nucleus. These results suggest that food deprivation modulates progestin receptor binding and PRIR in a site-specific manner. In addition, the effects of food deprivation on neural ERIR and PRIR are significantly different. nutritional infertility, progestin receptor, estrogen receptor, estrous behavior, hamsters, ventromedial hypothalamus, preoptic area MANY ENVIRONMENTAL FACTORS, including food availability, photoperiod, temperature, and social cues, can influence the reproductive performance of mammals. Almost every component of reproduction including puberty, ovulation, reproductive behavior, and lactation demand energy. Therefore, it is not surprising that food availability is one of the most important factors regulating mammalian reproduction (8). In female mammals, undernutrition delays puberty, interrupts menstrual and estrous cycles (8,30) and prevents the occurrence of estrous behavior in a variety of species, including hamsters (11,17,20). The neural mechanisms underlying nutritional infertility have attracted a great deal of interest. Food restriction alters the secretion of pituitary gonadotropins and gonadal steroids. This response is thought to be primarily due to the suppression of GnRH release (8,16,23,30). The activity of GnRH neurons in forebrain of underfed hamsters appears to decrease, which is reflected by the suppression of Fos-like immunoreactivity (1). In addition to the influence of metabolic manipulations on reproductive phys...

Deficits in Progesterone-Facilitated Sexual Behaviors and Forebrain Estrogen and Progestin Receptors in Obese Female Zucker Rats

“…Food-restricted, OVX postpubertal lambs showing reduced LH secretion were found to have a similar ER profile to fasted hamsters: diminished ER-IR in the VMH with elevated ER-IR in the MPOA [13]. Our data on estradiol-induced PR-IR, in contrast, are similar to those obtained in food-deprived hamsters, showing a reduction in the number of cells containing estradiol-induced PR-IR in the MPOA [10]. These data also resemble those obtained in infertile, obese db/db mice, which show deficits in accumulation of radiolabeled progesterone in several hypothalamic and limbic brain regions [49].…”

“…In female hamsters, for example, food deprivation or inhibition of metabolic fuel oxidation retards estrous cyclicity, reduces the display of sexual receptivity and VMN populations of ERs, and increases the concentration of ERs in the MPOA [1]. Concentrations of estradiol-induced PRs in the MPOA and medial amygdala are also reduced in food-deprived, OVX hamsters [10]. In mice and sheep, food restriction delays puberty, inhibits LH release and reduces hypothalamic ER populations [11, 12, 13].…”

The medial preoptic area is necessary for sexual odor preference, but not sexual solicitation, in female Syrian hamsters

“…Neurons in MPOA express receptors for estradiol and progesterone (Du et al, 1996; Li et al, 1993), and gonadal steroids strongly regulate other precopulatory behaviors that are disrupted following MPOA lesions, such as ultrasonic vocalizations (Floody, 1989; Floody et al, 1979). Although there is evidence in rats to suggest that estrogen alone or estrogen plus progesterone treatment may enhance the preference for male stimuli in females (Clark et al, 2004; Xiao et al, 2005), this does not appear to be the case in either mice (Moncho-Bogani et al, 2004) or hamsters (Eidson et al, 2007).…”

Food Restriction During Lactation Results in Prolonged Hyposensitivity to the Positive‐Feedback Effects of Oestradiol

“…The anteroventral preoptic area (AVPV) is regarded as a major site of oestrogen positive‐feedback and, for oestrogen to stimulate an LH surge, it must activate oestrogen receptors (ER) within this area (21, 22). One effect of ER activation within the AVPV is the synthesis of PR which, when activated either by progesterone itself or through ligand‐independent activation, facilitates LH release (16, 22), and this process may be compromised in situations of negative energy balance (23, 24).…”