Lemos V S, Bucher B, Côrtes S F, Takeda K
Université Louis Pasteur de Strasbourg, Laboratoire de Pharmacologie et Physiopathologie Cellulaires-CNRS URA 600, Illkirch, France.
Eur J Neurosci. 1997 Jun;9(6):1144-52. doi: 10.1111/j.1460-9568.1997.tb01468.x.
The effects of neuropeptide Y on the intracellular level of Ca2+ ([Ca2+]i) were studied in cultured rat adrenal chromaffin cells loaded with fura-2. A proportion (16%) of cells exhibited spontaneous rhythmic [Ca2+]i oscillations. In silent cells, oscillations could be induced by forskolin and 1,9-dideoxyforskolin. This action of forskolin was not modified by H-89, an inhibitor of protein kinase A. Spontaneous [Ca2+]i fluctuations and [Ca2+]i fluctuations induced by forskolin- and 1,9-dideoxyforskolin were inhibited by neuropeptide Y. Increases in [Ca2+]i induced by 10 and 20 mM KCI but not by 50 mM KCI were diminished by neuropeptide Y. However, neuropeptide Y had no effect on [Ca2+]i increases evoked by (-)BAY K8644 and the inhibitory effect of neuropeptide Y on responses induced by 20 mM KCI was not modified by omega-conotoxin GVIA, consistent with neither L- nor N-type voltage-sensitive Ca2+ channels being affected by neuropeptide Y. Rises in [Ca2+]i provoked by 10 mM tetraethylammonium were not decreased by neuropeptide Y, suggesting that K+ channel blockade reduces the effect of neuropeptide Y. However, [Ca2+]i transients induced by 1 mM tetraethylammonium and charybdotoxin were still inhibited by neuropeptide Y, as were those to 20 mM KCI in the presence of apamin. The actions of neuropeptide Y on [Ca2+]i transients provoked by 20 and 50 mM KCI, 1 mM tetraethylammonium, (-)BAY K8644 and charybdotoxin were mimicked by 8-bromo-cGMP. In contrast, 8-bromo-cAMP did not modify responses to 20 mM KCI or 1 mM tetraethylammonium. The inhibitory effects of neuropeptide Y and 8-bromo-cGMP on increases in [Ca2+]i induced by 1 mM tetraethylammonium were abolished by the Rp-8-pCPT-cGMPS, an inhibitor of protein kinase G, but not by H-89. A rapid, transient increase in cGMP level was found in rat adrenal medullary tissues stimulated with 1 microM neuropeptide Y. Rises in [Ca2+]i produced by DMPP, a nicotinic agonist, but not by muscarine, were decreased by neuropeptide Y. Our data suggest that neuropeptide Y activates a K+ conductance via a protein kinase G-dependent pathway, thereby opposing the depolarizing action of K+ channel blocking agents and the associated rise in [Ca2+]i.
利用负载fura-2的培养大鼠肾上腺嗜铬细胞，研究了神经肽Y对细胞内钙离子水平（[Ca2+]i）的影响。一部分（16%）细胞呈现出自发性的[Ca2+]i节律性振荡。在静止细胞中，毛喉素和1,9 - 二脱氧毛喉素可诱导振荡。毛喉素的这一作用不受蛋白激酶A抑制剂H - 89的影响。神经肽Y可抑制自发性[Ca2+]i波动以及由毛喉素和1,9 - 二脱氧毛喉素诱导的[Ca2+]i波动。神经肽Y可减弱由10和20 mM氯化钾诱导的[Ca2+]i升高，但对50 mM氯化钾诱导的[Ca2+]i升高无影响。然而，神经肽Y对（ - ）BAY K8644诱发的[Ca2+]i升高无作用，且神经肽Y对20 mM氯化钾诱导反应的抑制作用不受ω - 芋螺毒素GVIA的影响，这表明L型和N型电压敏感性Ca2+通道均不受神经肽Y影响。神经肽Y未降低由10 mM四乙铵引发的[Ca2+]i升高，提示钾通道阻断可降低神经肽Y的作用。然而，由1 mM四乙铵和蝎毒素诱导的[Ca2+]i瞬变仍受神经肽Y抑制，在蜂毒存在下由20 mM氯化钾诱导的[Ca2+]i瞬变也受其抑制。神经肽Y对由20和50 mM氯化钾、1 mM四乙铵、（ - ）BAY K8644和蝎毒素引发的[Ca2+]i瞬变的作用可被8 - 溴 - cGMP模拟。相比之下，8 - 溴 - cAMP未改变对20 mM氯化钾或1 mM四乙铵的反应。神经肽Y和8 - 溴 - cGMP对1 mM四乙铵诱导的[Ca2+]i升高的抑制作用可被蛋白激酶G抑制剂Rp - 8 - pCPT - cGMPS消除，但不受H - 89影响。在用1 microM神经肽Y刺激的大鼠肾上腺髓质组织中发现cGMP水平迅速短暂升高。神经肽Y可降低由烟碱激动剂DMPP而非毒蕈碱产生的[Ca2+]i升高。我们的数据表明，神经肽Y通过蛋白激酶G依赖性途径激活钾电导，从而对抗钾通道阻断剂的去极化作用以及相关的[Ca2+]i升高。
