Interactions between the Noradrenergic and Opioid Peptidergic Systems in Controlling the Electrical Activity of Luteinizing Hormone-Releasing Hormone Pulse Generator in Ovariectomized Rats

Nishihara, Masugi; Hiruma, Hiromi; Kimura, Fukuko

doi:10.1159/000125909

Cited by 61 publications

(33 citation statements)

References 29 publications

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“…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.…”

mentioning

confidence: 99%

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

Murata

Wakabayashi

Sakamoto

et al. 2011

Journal of Reproduction and Development

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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...

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confidence: 99%

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

Murata

Wakabayashi

Sakamoto

et al. 2011

Journal of Reproduction and Development

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“…Because SP did not modify GnRH release in animals with altered plasma gonadal steroids levels, we infer that gonadal steroids play an important role in the action of SP on GnRH release into the pituitary portal blood. One of the possible mechanisms explaining this steroid influence of SP action on hypothalamic GnRH neurons is that SP exerts its effect through the other inhibitory and/or stimulatory neurons controlling GnRH release into pituitary portal blood whose activity closely depends on the levels of circulating gonadal steroids [50, 51, 52, 53, 54, 55, 56]. …”

Section: Discussionmentioning

confidence: 99%

Increase of Gonadotropin-Releasing Hormone Concentration in Pituitary Portal Blood after Substance P Administration in Male Rats

Walczewska¹,

Szkudlarek²,

Jakubowska-Naziemblo³

et al. 1998

Neuroendocrinology

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Substance P (SP) affects gonadotropin release from the anterior pituitary gland. In the present study we tested whether SP exerts this effect through GnRH release into pituitary portal blood in intact male rats (INT), orchidectomized rats with s.c. chronically implanted empty Silastic capsule (ORCX), testosterone capsule (ORCX + T), and 17β-estradiol capsule (ORCX + E₂). The pituitary glands were exposed by the transpharyngeal approach under urethane-chloralose anesthesia. Then, the stalk portal vessels were cut and three 30-min portal blood samples were collected. Each first sample of blood was treated as a control before 0.2 ml injection of normal saline, 5 µg, or 25 µg of SP in 0.2 ml of normal saline into the internal carotid artery. GnRH concentration in the purified portal plasma were measured by RIA. Injection of SP into the internal carotid artery caused a significant increase in GnRH concentration in pituitary portal plasma only in INT rats. The higher dose of SP markedly increased GnRH concentration in the 1st blood sample (p < 0.001) and in the 2nd blood sample GnRH concentration was lower but still significant higher than prior SP injection (p < 0.05). The lower dose of SP increased GnRH concentration later, only in the 2nd portal blood sample after intracarotid SP injection (p < 0.001). Injection of normal saline had no effect on GnRH concentration in pituitary portal blood in INT rats. In ORCX, ORCX testosterone- and estrogen-implanted rats portal plasma GnRH concentrations were not changed significantly after injection of both doses of SP. These results indicate that SP stimulates GnRH release into pituitary portal blood and the influence of SP on GnRH neurons depends on the levels of circulating gonadal steroid hormones.

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“…The invariable association between these MUA volleys and the initiation of LH pulses (Fig. 1) observed under a variety of experimental circumstances in the rhesus monkey (5-12), rat (13)(14)(15)(16)(17)(18), and…”

mentioning

confidence: 91%

Estradiol and the inhibition of hypothalamic gonadotropin-releasing hormone pulse generator activity in the rhesus monkey.

Ördög

Knobil

1995

Proc. Natl. Acad. Sci. U.S.A.

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In mammals, gonadal function is controlled by a hypothalamic signal generator that directs the pulsatile release of gonadotropin-releasing hormone (GnRH) and the consequent pulsatile secretion of luteinizing hormone. In female rhesus monkeys, the electrophysiological correlates of GnRH pulse generator activity are abrupt, rhythmic increases in hypothalamic multiunit activity (MUA volleys), which represent the simultaneous increase in firing rate of individual neurons. MUA volleys are arrested by estradiol, either spontaneously at midcycle or after the administration of the steroid. Multiunit recordings, however, provide only a measure of total neuronal activity, leaving the behavior of the individual cells obscure. This study was conducted to determine the mode of action of estradiol at the level of single neurons associated with the GnRH pulse generator. Twentythree such single units were identified by cluster analysis of multiunit recordings obtained from a total of six electrodes implanted in the mediobasal hypothalamus of three ovariectomized rhesus monkeys, and their activity was monitored before and after estradiol administration. The bursting of all 23 units was arrested within 4 h of estradiol administration although their baseline activity was maintained. The bursts of most units reappeared at the same time as the MUA volleys, the recovery of some was delayed, and one remained inhibited for the duration of the study (43 days). The results indicate that estradiol does not desynchronize the bursting of single units associated with the GnRH pulse generator but that it inhibits this phenomenon. The site and mechanism of action of estradiol in this regard remain to be determined.

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Interactions between the Noradrenergic and Opioid Peptidergic Systems in Controlling the Electrical Activity of Luteinizing Hormone-Releasing Hormone Pulse Generator in Ovariectomized Rats

Cited by 61 publications

References 29 publications

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

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

Increase of Gonadotropin-Releasing Hormone Concentration in Pituitary Portal Blood after Substance P Administration in Male Rats

Estradiol and the inhibition of hypothalamic gonadotropin-releasing hormone pulse generator activity in the rhesus monkey.

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