Contents lists available at ScienceDirect Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet Research article Facilitatory and inhibitory role of central amylin administration in the regulation of the gonadotropin-releasing hormone pulse generator activity in goats Yuri Kitagawa, Takuya Sasaki, Reika Suzumura, Ai Morishima, Ryoki Tatebayashi, Assadullah, Nahoko Ieda, Yasuhiro Morita, Shuichi Matsuyama, Naoko Inoue, Yoshihisa Uenoyama, Hiroko Tsukamura, Satoshi Ohkura* Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan ARTICLE INFO Keywords: Amylin Calcitonin receptor GnRH pulse generator KNDy neurons Multiple unit activity Ruminants ABSTRACT Pulsatile gonadotropin-releasing hormone (GnRH) secretion is essential for regulating reproductive functions in mammals. GnRH pulses are governed by a neural mechanism that is termed the GnRH pulse generator. In the present study, we investigated the role of central calcitonin receptor (CTR) signaling in the regulation of the GnRH pulse generator activity in ovariectomized goats by administering amylin, an endogenous ligand for CTR, into the lateral ventricle. GnRH pulse generator activity was measured using multiple unit activity (MUA) re- cordings in the mediobasal hypothalamus. We analyzed changes in the interval of characteristic increases in MUA (MUA volleys). The MUA volley interval shortened immediately after amylin administration, followed by prolonged intervals. Double in situ hybridization for KISS1 (kisspeptin gene) and CALCR (CTR gene) revealed that low expression levels of CALCR were found in the arcuate kisspeptin neurons, which is suggested as the main population of neurons, involved in GnRH pulse generator activity. These results suggest that central amylin-CTR signaling has a biphasic role in the regulation of GnRH pulse generator activity by acting on cells other than the arcuate kisspeptin neurons in goats. 1. Introduction The frequency of pulsatility of gonadotropin-releasing hormone (GnRH) secretion with physiological frequency is important in main- taining normal reproduction in mammals, as evidenced by the sup- pression of gonadotropin release in rhesus monkeys following chronic GnRH administration [1]. Alterations in the frequency of pulsatile GnRH secretion are dependent on reproductive status: a higher fre- quency of pulsatile GnRH secretion is observed in the follicular phase, which includes the accelerated development of ovarian follicles, compared with the luteal phase in ewes [2]. Furthermore, pulsatile GnRH administration at a higher frequency results in a higher baseline of pulsatile luteinizing hormone (LH) secretion in ovariectomized (OVX) ewes with hypothalamo-pituitary disconnection [3]. Taken to- gether, these studies show that the frequency of pulsatile GnRH secre- tion is a key determinant for gonadotropin release, which in turn sti- mulates folliculogenesis. Pulsatile GnRH secretion is governed by a neural mechanism called the GnRH pulse generator. Accumulating evidence has indicated that kisspeptin neurons in the hypothalamic arcuate nucleus (ARC) are the https://doi.org/10.1016/j.neulet.2020.135276 Received 31 December 2019; Received in revised form 30 June 2020; Accepted 22 July 2020 Abbreviations: ARC, arcuate nucleus; BST, bed nucleus stria terminalis; CTR, calcitonin receptor; DIG, digoxigenin isothiocyanate; DMH, dorsomedial hypothalamic nucleus; FITC, fluorescein isothiocyanate; GnRH, gonadotropin-releasing hormone; LH, luteinizing hormone; LV, lateral ventricle; MBH, mediobasal hypothalamus; MPOA, medial preoptic area; MUA, multiple unit activity; OVX, ovariectomized; POA, preoptic area; PVN, paraventricular hypothalamic nucleus; SCN, su- prachiasmatic nucleus; SD, standard deviation; VMH, ventromedial hypothalamic nucleus ⁎ Corresponding author at: Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan. E-mail addresses: kitagawa.yuri@c.mbox.nagoya-u.ac.jp (Y. Kitagawa), sasaki.takuya.1991@gmail.com (T. Sasaki), suzumura.reika@f.mbox.nagoya-u.ac.jp (R. Suzumura), a.m.uv_wo.15over4@icloud.com (A. Morishima), tatebayashi.ryoki@d.mbox.nagoya-u.ac.jp (R. Tatebayashi), assadullahdost@yahoo.com (Assadullah), nahoko.ieda@nagoya-u.jp (N. Ieda), ymorita@agr.nagoya-u.ac.jp (Y. Morita), shuichim@agr.nagoya-u.ac.jp (S. Matsuyama), ninoue@agr.nagoya-u.ac.jp (N. Inoue), uenoyama@nagoya-u.jp (Y. Uenoyama), htsukamura@nagoya-u.jp (H. Tsukamura), saohkura@agr.nagoya-u.ac.jp (S. Ohkura). Neuroscience Letters 736 (2020) 135276 0304-3940/ © 2020 Elsevier B.V. All rights reserved. T