Mechanisms of the Modulation of Pacemaker Activity by GnRH Peptides in the Terminal Nerve-GnRH Neurons(Endocrinology)
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概要
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According to our working hypothesis, the terminal nerve (TN)-gonadotropin releasing hormone (GnRH) system functions as a neuromodulatory system that regulates many long-lasting changes in animal behaviors. We have already shown by using in vitro whole brain preparations of a small fish (dwarf gourami) that the pacemaker activities of TN-GnRH neurons are modulated biphasically by salmon GnRH, which is the same molecular species of GnRH produced by TN-GnRH neurons themselves ; the modulation consists of initial transient decrease and late increase of firing frequency. In the preset study, we investigated the possible involvement of Ca^<2+> release from intracellular store and voltage dependent Ca^<2+> currents in the modulation of pacemaker activities. Pharmacological blockade of Ca^<2+> release from intracellular stores or apamin-sensitive Ca^<2+>-activated K^+ current inhibited the initial transient decrease of firing frequency by sGnRH. On the other hand, bath application of Ca^<2+> channel blockers Ni^<2+> or La^<3+> slowed down the pacemaker frequency and attenuated the rate of the late increase of pacemaker frequency by GnRH. Furthermore, voltage-clamp experiments suggested that low-voltage-activated (LVA) Ca^<2+> current and high-voltage-activated (HVA) Ca^<2+> current were present in the TN-GnRH neurons, and bath application of GnRH shifted the activation threshold of HVA Ca^<2+> current to more negative potentials. These results suggest that (1) sGnRH induces Ca^<2+> release from intracellular stores and activates apaminsensitive Ca^<2+>-activated K^+ current so that it decreases the frequency of pacemaker activity in the initial phase, (2) some kinds of Ca^<2+> currents contribute to the generation and modulation of pacemaker activities, and (3) HVA Ca^<2+> current is facilitated by sGnRH so that it increases the frequency of pacemaker activity in the late phase.
- 社団法人日本動物学会の論文
- 2002-01-25
著者
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Abe Hideki
Misaki Marine Biological Station Graduate School Of Science The University Of Tokyo:(present Address
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Oka Yoshitaka
Misaki Marine Biological Station Grad. Sch. Sci. Univ. Of Tokyo
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Oka Yoshitaka
Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo
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