Schaad N C, Vanecek J, Rodriguez I R, Klein D C, Holtzclaw L, Russell J T
Section on Neuroendocrinology, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
Mol Pharmacol. 1995 May;47(5):923-33.
Vasoactive intestinal peptide (VIP) receptor density is high in the pineal gland, which receives VIP innervation and responds to VIP with a relatively small increase in cAMP and cGMP levels. In the present study, we show that VIP (5-200 nM) treatment increased the intracellular calcium concentration ([Ca2+]i) in 64% of isolated individual pinealocytes; in comparison, norepinephrine (NE) elevated [Ca2+]i in 93% of the cells and produced more robust responses. Analysis of the role of second messengers indicated that [Ca2+]i was strongly elevated by cGMP analogs, but not by cAMP analogs. The nitric oxide-releasing agent S-nitro-N-acetylpenicillamine and 2,2-diethyl-1-nitroxyhydraxine also elevated [Ca2+]i. Investigation of the mechanisms revealed that responses to VIP or 8-bromo-cGMP involved Ca2+ influx, as did the plateau component of the response to NE; the large rapid component of the response to NE, however, appeared to reflect release from intracellular stores. Pharmacological studies indicated that the VIP-induced Ca2+ influx was mediated by a retinal rod-type cyclic nucleotidegated cation channel, expression of which was confirmed by reverse transcription-polymerase chain reaction analysis. These observations indicate that fundamentally different mechanisms generate the responses to NE and VIP. The dominant effect of VIP causing transient elevation of [Ca2+]i appears to be through cGMP gating aI-cis-diltiazem-sensitive rod-type cyclic nucleotide-gated cation channel. In contrast, the dominant effect of NE on [Ca2+]i is due to enhanced Ca2+ release from intracellular stores; the plateau component is due to influx through aI-cis-diltiazem-insensitive channel.
血管活性肠肽（VIP）受体在松果体中的密度很高，松果体接受VIP神经支配，并对VIP做出反应，使环磷酸腺苷（cAMP）和环磷酸鸟苷（cGMP）水平有相对较小的升高。在本研究中，我们发现，用VIP（5 - 200 nM）处理可使64%的分离单个松果体细胞内的钙浓度（[Ca2+]i）升高；相比之下，去甲肾上腺素（NE）可使93%的细胞内[Ca2+]i升高，并产生更强有力的反应。对第二信使作用的分析表明，cGMP类似物可使[Ca2+]i大幅升高，但cAMP类似物则无此作用。释放一氧化氮的试剂S - 硝基 - N - 乙酰青霉胺和2,2 - 二乙基 - 1 - 硝氧肼也可使[Ca2+]i升高。机制研究表明，对VIP或8 - 溴 - cGMP的反应涉及Ca2+内流，对NE反应的平台期成分也是如此；然而，对NE反应的快速大幅成分似乎反映的是细胞内储存钙的释放。药理学研究表明，VIP诱导的Ca2+内流是由视杆细胞型环核苷酸门控阳离子通道介导的，逆转录 - 聚合酶链反应分析证实了该通道的表达。这些观察结果表明，对NE和VIP的反应是由根本不同的机制产生的。VIP导致[Ca2+]i短暂升高的主要作用似乎是通过cGMP门控对1,4 - 二氢 - 2,6 - 二甲基 - 5 - 硝基 - 4 - (2 - 三氟甲基苯基) - 3,5 - 吡啶二甲酸异丁酯敏感的视杆细胞型环核苷酸门控阳离子通道。相比之下，NE对[Ca2+]i的主要作用是由于细胞内储存钙的释放增强；平台期成分是由于通过对1,4 - 二氢 - 2,6 - 二甲基 - 5 - 硝基 - 4 - (2 - 三氟甲基苯基) - 3,5 - 吡啶二甲酸异丁酯不敏感的通道内流所致。
