Kaku K, Tsuchiya M, Matsuda M, Inoue Y, Kaneko T, Yanaihara N
Endocrinology. 1985 Dec;117(6):2371-5. doi: 10.1210/endo-117-6-2371.
We examined the effects of environmental light and prior treatment with an agonist on vasoactive intestinal polypeptide (VIP) binding and VIP stimulation of cAMP accumulation in the rat pineal gland. VIP binding to pinealocytes and cAMP accumulation in response to VIP were significantly increased in animals kept exposed to constant light compared to those in animals experiencing a dark night before the experiments. Scatchard analysis of [125I]VIP binding indicated the presence of two classes of binding sites: high affinity, low capacity sites and low affinity, high capacity sites. The increased VIP binding to pinealocytes in rats maintained in constant light was attributed to an increase in the number of available VIP receptors at both high and low affinity sites. The affinity of VIP binding to cells was not affected by exposure of the animals to light. VIP stimulation of cAMP accumulation was not inhibited by d,l-propranolol. Prior treatment of pinealocytes with VIP decreased [125I]VIP binding by reducing the number of receptors and significantly inhibited subsequent VIP stimulation of cAMP accumulation. Prior treatment with norepinephrine did not alter the number of VIP receptors. Our results strongly suggest that VIP is a neuromodulator of pineal function.
我们研究了环境光以及用激动剂预先处理对大鼠松果体中血管活性肠肽（VIP）结合和VIP刺激的环磷酸腺苷（cAMP）积累的影响。与在实验前经历黑夜的动物相比，持续暴露于光照下的动物中，VIP与松果体细胞的结合以及对VIP的cAMP积累显著增加。对[125I]VIP结合的Scatchard分析表明存在两类结合位点：高亲和力、低容量位点和低亲和力、高容量位点。持续光照下的大鼠中VIP与松果体细胞结合增加，这归因于高亲和力和低亲和力位点上可用VIP受体数量的增加。VIP与细胞结合的亲和力不受动物光照暴露的影响。d，l-普萘洛尔不抑制VIP对cAMP积累的刺激。用VIP预先处理松果体细胞可通过减少受体数量降低[125I]VIP结合，并显著抑制随后VIP对cAMP积累的刺激。用去甲肾上腺素预先处理不会改变VIP受体的数量。我们的结果有力地表明VIP是松果体功能的神经调节剂。
