Effects of Brief Exposure of Male Pheromone on Multiple-Unit Activity at Close Proximity to Kisspeptin Neurons in the Goat Arcuate Nucleus

Abstract

Abstract. Exposure of females to the male pheromone induces pulsatile release of gonadotropin-releasing hormone (GnRH) in goats. Recently, kisspeptin neurons in the arcuate nucleus (ARC) have been suggested to represent the proximate source of the GnRH pulse generator. In this study, we examined the effects of the pheromone on multipleunit activity (MUA) in female goats fitted with recording electrodes aimed at the ARC kisspeptin neurons. In all eight goats, periodic bursts in MUA (MUA volleys), which were considered to be electrophysiological manifestations of the GnRH pulse generator, were observed. The mean intervolley interval (T) during the control period was calculated in each goat that was then exposed to the male pheromone for 1 sec at timings of 1/4 T, 1/2 T or 3/4 T after one regularly occurring MUA volley. An instantaneous rise in MUA was observed immediately after the exposure regardless of timing. Exposure at a timing of 3/4 T resulted in an MUA volley within 60 sec following the instantaneous rise in all goats. In contrast, an MUA volley was induced in only 2 goats by exposure at 1/2 T, while exposure at 1/4 T failed to induce an MUA volley in any goats. These results suggest that transmission of the pheromone signal to the ARC, represented by an instantaneous rise, activates the GnRH pulse generator. Moreover, the timing-dependent pheromone action in inducing an MUA volley indicates that the GnRH pulse generator has a refractory period for the pheromone signal after the burst. Key words: GnRH pulse generator, Goat, Kisspeptin, Male effect, Pheromone (J. Reprod. Dev. 57 : 197-202, 2011) n goats and sheep, exposure of seasonally anestrous females to the primer pheromone secreted by sexually mature males results in an out-of-seasonal ovulation [1][2][3][4]. Since the initial endocrine event following reception of the pheromone is the stimulation of pulsatile luteinizing hormone (LH) secretion, it has been thought that the central target of the pheromone signal is the GnRH pulse generator [1,[3][4][5], i.e., the neural substrate that generates intermittent GnRH discharges into the portal vessels, thereby regulating pulsatile LH secretion into the peripheral circulation [6,7].Although the neural identity of the GnRH pulse generator per se was unclear, it was possible to measure its activity by recording multiple-unit activity (MUA) at the mediobasal hypothalamus. It has been demonstrated that electrophysiological manifestations of the GnRH pulse generator are represented as characteristic increases in MUA (MUA volleys) that are exclusively associated with LH pulses in the monkey [8], rat [9] and goat [10,11]. It might be that observed MUA volleys reflect the pulsatile activation of GnRH nerve terminals as they traverse en passant to the ME. Using this technique, Hamada et al. [12] showed that exposure of the female goat to male hair used as a pheromone source promptly induced an MUA volley, demonstrating for the first time that the pheromone action is in fact intimately associated with the GnRH pul...

The Effects of Chronic Subcutaneous Administration of an Investigational Kisspeptin Analog, TAK-683, on Gonadotropin-Releasing Hormone Pulse Generator Activity in Goats

“…Hair collected from the head region of an intact adult male goat was used as a pheromone source [37,38,39]. A small hair sample (approx.…”

“…A small hair sample (approx. 1.0 g) was placed between two plastic cups, with the bottom of the inner cup replaced with a mesh [37]. Upon exposure, the goat's muzzle was inserted in the cup for 10 s. Senktide (Ana Spec, Inc., Fremont, Calif., USA) was dissolved in saline (50 nmol/2 ml), and the solution was sterilized by passing through a 0.22-µm filter.…”

“…We also examined the effects of male pheromones and senktide, a selective agonist of the neurokinin B (NKB) receptor, on GnRH pulse generator activity and LH secretion during chronic TAK-683 administration. In goats, male pheromones [37,38,39] and senktide [40] both stimulate pulsatile LH secretion via the activation of the GnRH pulse generator. …”

Desenvolvimento reprodutivo de cabritas Saanen submetidas ao efeito macho no período peri-púbere

“…Esse fenômeno, denominado "efeito macho", pode ser induzido por machos sexualmente ativos (FIOL; QUINTANS; UNGERFELD, 2010; DELGADILLO et al, 2011), fêmeas e machos castrados androgenizados (MELLADO e HERNANDEZ, 1996;KAKUMA et al, 2007) e pela exposição a odores masculinos da mesma espécie (OKAMURA et al, 2010;MURATA et al, 2011) ou de outra espécie ).…”

“…No hipotálamo, as kisspeptinas e seu receptor estão associados a regulação da ação dos estrógenos, da progesterona e do estímulo social na atividade dos neurônios do GnRH (D' ANGLEMONT DE TASSIGNY;MURATA et al, 2011;KITAHASHI;PARHAR, 2013;OKAMURA;YAMAMURA;WAKABAYASHI, 2013). Assim, a expressão do gene kiss1 e do receptor de kisspeptinas no hipotálamo em animais sexualmente ativos encontra-se aumentada quando comparada a expressão dessas moléculas em animais sexualmente imaturos (KAISER; KUOHUNG, 2005;NAVARRO et al, 2009).…”