Expression of kisspeptin protein in hypothalamus and LH profile of growing female lambs

Mating-induced increase in Kiss1 mRNA expression in the anteroventral periventricular nucleus prior to an increase in LH and testosterone release in male rats

Kisspeptin has an indispensable role in gonadotropin-releasing hormone/gonadotropin secretion in mammals. In rodents, kisspeptin neurons are located in distinct brain regions, namely the anteroventral periventricular nucleus-periventricular nucleus continuum (AVPV/PeN), arcuate nucleus (ARC), and medial amygdala (MeA). Among them, the physiological role of AVPV/PeN kisspeptin neurons in males has not been clarified yet. The present study aims to investigate the acute effects of the olfactory and/or mating stimulus with a female rat on hypothalamic and MeA Kiss1 mRNA expression, plasma luteinizing hormone (LH) and testosterone levels in male rats. Intact male rats were exposed to the following stimuli: exposure to clean bedding; exposure to female-soiled bedding as a female-olfactory stimulus; exposure to female-soiled bedding and mating stimulus with a female rat. The mating stimulus significantly increased the number of the AVPV/PeN Kiss1 mRNA-expressing cells in males within 5 minutes after the exposure, and significantly increased LH and testosterone levels, followed by an increase in male sexual behavior. Whereas, the males exposed to female-soiled bedding showed a moderate increase in LH levels and no significant change in testosterone levels and the number of the AVPV/PeN Kiss1 mRNA-expressing cells. Importantly, none of the stimuli affected the number of Kiss1 mRNA-expressing cells in the ARC and MeA. These results suggest that the mating-induced increase in AVPV/PeN Kiss1 mRNA expression may be, at least partly, involved in stimulating LH and testosterone release, and might consequently ensure male mating behavior. This study would be the first report suggesting that the AVPV/PeN kisspeptin neurons in males may play a physiological role in ensuring male reproductive performance.

Collagen, glycosaminoglycans and matrix metalloproteinase-2 and metalloproteinase-9 in the cervix of the ewe during prepubertal development

The tortuous nature of the ovine cervix restricts the transcervical passage of the cannula, and many studies have aimed to understand the endocrine mechanism of the remodelling of cervical tissue in adult ewe. However, little is known about the remodelling of the cervical tissue during the prepubertal development of the lambs. To obtain histochemical and biochemical evidence about the nature of the prepubertal development of the cervix of the ewe, cervices of Corriedale lambs obtained at 0, 1, 2, 4, 6 and 8 months of age (n = 5 to 6 in each) were processed. Neutral and acidic glycosaminoglycans (by PAS-Alcian stain) were weakly in the cervical stroma and not shown change during the development, whereas the percentage volume of fibrillar collagen (by van Gieson stain) increases throughout the experimental period in the superficial fold stroma and deep wall stroma (p < 0.05). The relative cervical weight (g/kg of body weight) and the collagen concentration (by spectrophotometry, mg/mg wet tissue) showed an early decreasing phase from months 0 to 4 and a later increasing phase from months 4 to 8 (p < 0.05). The latent form of matrix metalloproteinase-2 (MMP-2) detected by gelatin zymography (ng/mg protein) decreased from months 0 to 2 and increased from months 4 to 8, whereas the activated form decreased from months 0 to 2, remained low until month 6 and then recovered on month 8 (p < 0.0001). Data suggest that the relative cervical weight biphasic pattern during the development is related to MMP-2-dependent changes in the collagen content.

Regulation of GnRH pulsatility in ewes

Early work in ewes provided a wealth of information on the physiological regulation of pulsatile gonadotropin-releasing hormone (GnRH) secretion by internal and external inputs. Identification of the neural systems involved, however, was limited by the lack of information on neural mechanisms underlying generation of GnRH pulses. Over the last decade, considerable evidence supported the hypothesis that a group of neurons in the arcuate nucleus that contain kisspeptin, neurokinin B and dynorphin (KNDy neurons) are responsible for synchronizing secretion of GnRH during each pulse in ewes. In this review, we describe our current understanding of the neural systems mediating the actions of ovarian steroids and three external inputs on GnRH pulsatility in light of the hypothesis that KNDy neurons play a key role in GnRH pulse generation. In breeding season adults, estradiol (E₂) and progesterone decrease GnRH pulse amplitude and frequency, respectively, by actions on KNDy neurons, with E₂ decreasing kisspeptin and progesterone increasing dynorphin release onto GnRH neurons. In pre-pubertal lambs, E₂ inhibits GnRH pulse frequency by decreasing kisspeptin and increasing dynorphin release, actions that wane as the lamb matures to allow increased pulsatile GnRH secretion at puberty. Less is known about mediators of undernutrition and stress, although some evidence implicates kisspeptin and dynorphin, respectively, in the inhibition of GnRH pulse frequency by these factors. During the anoestrus, inhibitory photoperiod acting via melatonin activates A15 dopaminergic neurons that innervate KNDy neurons; E₂ increases dopamine release from these neurons to inhibit KNDy neurons and suppress the frequency of kisspeptin and GnRH release.