Mechanisms of GABA-mediated inhibition of the angiotensin II-induced cytosolic Ca2+ increase in rat subfornical organ neurons
Mechanisms of GABA-mediated inhibition of the angiotensin II-induced cytosolic Ca2+ increase in rat subfornical organ neurons
复制标题
GABA介导的抑制血管紧张素II诱导的大鼠穹窿下器官神经元胞质Ca2+增加的机制
DOI：
10.1016/j.brainres.2021.147451
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发表时间：
2021
期刊：
影响因子：
2.9
通讯作者：
Izumi Shibuya
中科院分区：
文献类型：
--
作者：
Yu Izumisawa ;Kenji Ito ;Keisuke Sugita ;Tazuyo Arai ;Hina Kokudo ;Naoki Kitamura ;Izumi Shibuya
穹窿下器官（SFO）中的神经元感知神经递质和循环体液因子如血管紧张素II（AII）和心钠素（ANP），并调节包括饮酒行为在内的多种生理功能。我们最近报道，在纳摩尔浓度的AII诱导急性分离的SFO神经元的持续[Ca ~（2+）] i增加，这种效果的AII是可逆的GABA抑制。本研究采用钙离子成像和膜片钳技术研究GABA的抑制机制。GABA在90%以上的AII反应神经元中抑制AII诱导的持续性[Ca ~（2+）] i增加，而另外两种SFO抑制性配体ANP和甘丙肽分别在约60%和30%的神经元中抑制AII诱导的持续性[Ca ~（2+）] i增加。GABA和GABA B受体激动剂蝇蕈醇和巴氯芬模拟GABA的抑制作用。GABA受体亚型的参与证实了逆转GABA介导的抑制只有当GABA和GABA受体拮抗剂甲碘荷包牡丹碱和CGP 55845都存在。GABA受体激动剂巴氯芬可快速可逆地抑制电压钳电生理学中以Ba 2+为电荷载体（IBa）记录的电压门控Ca 2+通道（VGCC）电流。巴氯芬对IBA的抑制作用被CGP 55845拮抗，证实GABA B受体参与;被N-乙基马来酰亚胺减少，表明下游Gi介导的作用;并被大的前脉冲部分消除，表明电压依赖性。通过应用N-、P/Q-和L-型VGCC的选择性阻断剂（分别为ω-芋螺毒素GVIA、ω-蛇曲霉毒素IVA和硝苯地平），巴氯芬对IBainlavin的影响程度降低。总之，我们的研究表明，GABA抑制AII诱导的[Ca 2 +] i增加是由GABAA和GABAB受体介导的，并且与Gi蛋白相关的GABAB受体抑制SFO神经元中通过VGCC的Ca 2+内流。
Neurons in the subfornical organ (SFO) sense both neurotransmitters and circulating humoral factors such as angiotensin II (AII) and atrial natriuretic peptide (ANP), and regulate multiple physiological functions including drinking behavior. We recently reported that AII at nanomolar concentrations induced a persistent [Ca2+]iincrease in acutely dissociated SFO neurons and that this effect of AII was reversibly inhibited by GABA. In the present study, we studied the inhibitory mechanism of GABA using Ca2+imaging and patch-clamp electrophysiology. The AII-induced persistent [Ca2+]iincrease was inhibited by GABA in more than 90% of AII-responsive neurons and by other two SFO inhibitory ligands, ANP and galanin, in about 60 and 30% of neurons respectively. The inhibition by GABA was mimicked by the GABAAand GABABreceptor agonists muscimol and baclofen. The involvement of both GABA receptor subtypes was confirmed by reversal of the GABA-mediated inhibition only when the GABAAand GABABreceptors antagonists bicuculline methiodide and CGP55845 were both present. The GABABagonist baclofen rapidly and reversibly inhibited voltage-gated Ca2+channel (VGCC) currents recorded in response to depolarizing pulses in voltage-clamp electrophysiology using Ba2+as a charge carrier (IBa). Baclofen inhibition of IBawas antagonized by CGP55845, confirming GABABreceptor involvement; was reduced by N-ethylmaleimide, suggesting downstream Gi-mediated actions; and was partially removed by a large prepulse, indicating voltage-dependency. The magnitude of IBainhibition by baclofen was reduced by the application of selective blockers for N-, P/Q-, and L-type VGCCs (ω-conotoxin GVIA, ω-agatoxin IVA, and nifedipine respectively). Overall, our study indicates that GABA inhibition of the AII-induced [Ca2+]iincrease is mediated by both GABAAand GABABreceptors, and that GABABreceptors associated with Gi proteins suppress Ca2+entry through VGCCs in SFO neurons.