| Project/Area Number |
09470020
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental physiology (including Physical medicine and Nutritional physiology)
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| Research Institution | University of Occupational and Environmental Health |
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Principal Investigator |
SHIBUYA Izumi University of Occupational and Environmental Health Department of Physiology, Associate Professor, 医学部, 助教授 (50162649)
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| Co-Investigator(Kenkyū-buntansha) |
UEZONO Yasuhito University of Occupational and Environmental Health Department of Pharmacology,, 医学部, 講師 (20213340)
UETA Yoichi University of Occupational and Environmental Health Department of Physiology, Le, 医学部, 講師 (10232745)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥11,600,000 (Direct Cost: ¥11,600,000)
Fiscal Year 1998: ¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1997: ¥9,100,000 (Direct Cost: ¥9,100,000)
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| Keywords | GABA_B receptors / Patch clamp / supraoptic nucleus (SON) / Action Potentials / Excitatory Postsynaptic Currents / Inhibitory Postsynaptic Currents / Voltage-dependent Ca^<2+> currents / Xenopus oocytes / 神経内分泌ニューロン / baclofen / CFTR / GIRK / スライスパッチクランプ / シナプス電流 / 膜電位依存性Ca電流 |
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| Research Abstract |
1)To elicidate the role of GABA_B receptors in the regulation of the magnocellular neurosecretory cells in the supraoptic nucleus (SON) of the hypothalamus, we measured the membrane potential, the firing frequency, and spontaneous excitatory and inhibitory postsynaptic currents (sEPSCs and sIPSCs) in rat SON slice preparations, and also the voltage-gated Ca^<2+> currents (VGC) of acutely dissociated rat SON neurons by the whole-cell patch-clamp technique. The selective GABAGABA_B agonist, baclofen suppressed the action potential discharge of SON neurons, without causing marked hyperpolarization. Baclofen educed the frequency of both the sEPSCs and sIPSCs without affecting the amplitude. The time constant of the decay phase of both the sEPSCs and sIPS Cs remained unchanged after baclofen application. The reduction of the frequency of the synaptic currents by baclofen was dose-dependent. Baclofen inhibited VGC also in a dose-dependent manner. Only the inhibition of N- and P/Q-types was significant. These results indicate that GABAGABA_B receptors are present both at the pre- and post-synaptic sites of SON neurons and mediate inhibition of EPSCs and IPSCs, and of N- and P/Q-type Ca^<2+> channels. These multiple inhibitory mechanisms mediated by pre- and postsynaptic GABAGABA_B receptors may play important roles in the regulation of SON neurons by the GABA neurons.
2)To investigate the signal transduction mechanism of GABAGABA_B receptor-mediated cellular responses, poly (A)^+ RNA derived from rat brain cortex was coexpressed with CFTR CI channls or with GIRK channels. We found that upon GABAGABA_B activation, the Gbetagamma released from PTX-sensitive G-proteins activates the adenylate cyclase type II, and this process requires Gs activation by Gs-coupled receptors. We also found that GABAGABA_B receptors activated the cloned GIRKs composed GIRK1 and GIRK2 as heteromultimers.
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