Neuroendocrine Control of the Ovarian Cycle of the Rat

Neuroendocrine Control of Gonadotropin Secretion

“…156,221 These ARC neurons also contain neurokinin B (NKB) and dynorphin and thus are referred to as KNDy cells. 177 The evidence in support of this hypothesis comes largely from reports that E 2 inhibits kisspeptin expression in this region, 155 an effect that has been consistently observed in rats and mice, 3 hamsters, 222 musk shrews, 223 sheep, 2 monkeys, 1 and humans. 224 Since kisspeptin stimulates GnRH release, these inhibitory effects of 5.…”

“…In rats, these actions generally correlate with the effects of progesterone on LH secretion, with acute exposure (for 3-8 h) enhancing the response to GnRH, and prolonged exposure (at least 48 h) inhibiting this response. 3 In women with deficient GnRH secretion, progesterone increased LH pulse amplitude in response to exogenous GnRH pulses, 142 an action that may contribute to the elevated response to GnRH observed during the normal luteal phase. 143 In monkeys, stimulatory effects of progesterone on the pituitary have been reported, 1 but these are not reflected in an increased response to GnRH in luteal phase animals.…”

“…However other ARC neurons containing NK3R would also be lesioned by the techniques used and this proposed role for ARC kisspeptin neurons in rodents remains controversial. 3 Finally, it is interesting to note that, at least in sheep, the same population of KNDy neurons may mediate the negative feedback actions of progesterone and estradiol, but do so via different transmitters (dynorphin and kisspeptin, respectively).…”

“…Also note that in some species (e.g., rodents and primates), the follicles also secrete progesterone, while in others (e.g., some primates, and rabbits) the corpus luteum also produces E 2 ; these steroid patterns have been omitted from this figure in the interests of simplicity. Hormonal patterns taken for panels A-D are based on data in women, 1 sheep, 2 rats, 3 and rabbits, 4 respectively. 5.…”

“…The third group of animals, which consists largely of rats, mice, and hamsters, has shortened both the follicular phase and luteal phase to 1 or 2 days and has estrous cycles that are 4 or 5 days in length. 3 The 4 days of the estrous cycle are usually referred to as estrus (ovulation and estrous behavior), metestrus (increasing progesterone), diestrus (falling progesterone and increasing E 2 ), and proestrus (peak E 2 ). There is also a peak in follicular progesterone secretion on the afternoon of proestrus (not shown in Figure 33.1) that induces estrous behavior early the next day.…”