Pattern of gonadotropin secretion along the estrous cycle of C57BL/6 female mice

Abstract

The pattern of gonadotropin secretion along the estrous cycle was elegantly described in rats. Less information exists about the pattern of gonadotropin secretion in gonad‐intact mice, particularly regarding the follicle‐stimulating hormone (FSH). Using serial blood collections from the tail‐tip of gonad‐intact C57BL/6 mice on the first day of cornification (transition from diestrus to estrus; hereafter called proestrus), we observed that the luteinizing hormone (LH) and FSH surge cannot be consistently detected since only one out of eight females (12%) showed increased LH levels. In contrast, a high percentage of mice (15 out of 21 animals; 71%) exhibited LH and FSH surges on the proestrus when a single serum sample was collected. Mice that exhibited LH and FSH surges on the proestrus showed c‐Fos expression in gonadotropin‐releasing hormone‐ (GnRH; 83.4% of co‐localization) and kisspeptin‐expressing neurons (42.3% of co‐localization) of the anteroventral periventricular nucleus (AVPV). Noteworthy, mice perfused on proestrus, but that failed to exhibit LH surge, showed a smaller, but significant expression of c‐Fos in GnRH (32.7%) and AVPVKisspeptin (14.0%) neurons. Finally, 96 serial blood samples were collected hourly in eight regular cycling C57BL/6 females to describe the pattern of LH and FSH secretion along the estrous cycle. Small elevations in LH and FSH levels were detected at the time expected for the LH surge. In summary, the present study improves our understanding of the pattern of gonadotropin secretion and the activation of central components of the hypothalamic–pituitary‐gonadal axis along the estrous cycle of C57BL/6 female mice.

Optogenetic stimulation of Kiss1ARC terminals in the AVPV induces surge-like luteinizing hormone secretion via glutamate release in mice

“…Secondly, the Kiss1 AVPV neurons infected with EYFP virus occupy only a small proportion (<5%). It is unlikely that this number of Kiss1 AVPV neurons with ChR2-EYFP could evoke an LH surge, because it was previously shown that mice failed to exhibit an LH surge when 14% of Kiss1 AVPV neurons were activated ( 48 ). At the same time, the LH dynamics are also different with Kiss1 AVPV cell bodies stimulation ( 16 ).…”

Estrous Cycle and Egg Release Resets with Light Entrainment Inspired by Neurodynamics in the Circadian Pacemaker

“…Typically, P-2 and P-1 are metestrus or diestrus, and P+1 is estrus. P+2 is estrous and metestrus (see also 34 ). We did not identify signi cant differences between estrous stages or between intact and ovariectomized females (Figure 3E, see also Figure S3).…”

Collection and Analysis of Vaginal Smears to Assess Reproductive Stage in Mice

“…It is characterized by an increase in E2 followed by the GnRH/LH surge usually occurring at the light/dark transition (Gusmao et al., 2022; Miller & Takahashi, 2014; Walmer et al., 1992). Estrus: The LH surge triggers the release of oocytes from the ovary (ovulation); this estrous stage is the period of sexual receptivity lasting ∼1 day, by the end of which E2 and LH levels return to basal (Goldman et al., 2007; Gusmao et al., 2022; Walmer et al., 1992). Metestrus and diestrus: Metestrus is followed by the diestrus stage, both of which are characterized by low basal levels of E2 and LH, together generally lasting 2 to 3 days (Goldman et al., 2007; Gusmao et al., 2022; Walmer et al., 1992).…”

“… Proestrus: This is the pre‐ovulatory stage, which lasts <12 to 24 hr. It is characterized by an increase in E2 followed by the GnRH/LH surge usually occurring at the light/dark transition (Gusmao et al., 2022; Miller & Takahashi, 2014; Walmer et al., 1992). Estrus: The LH surge triggers the release of oocytes from the ovary (ovulation); this estrous stage is the period of sexual receptivity lasting ∼1 day, by the end of which E2 and LH levels return to basal (Goldman et al., 2007; Gusmao et al., 2022; Walmer et al., 1992).…”