Fayolle C, Fillion M P, Barone P, Oudar P, Rousselle J C, Fillion G
Unit of Neuroimmunoendocrinological Pharmacology (UA 1113 CNRS), Pasteur Institute, Paris, France.
Fundam Clin Pharmacol. 1988;2(3):195-214. doi: 10.1111/j.1472-8206.1988.tb00632.x.
5-HT binding sites of the 5-HT1 type are heterogeneous and appear to comprise several subtypes (5-HT1A, 5-HT1B and 5-HT1C); their physiological role is as yet unclear. The stimulation of adenylate cyclase induced by 5-HT has been investigated in membrane fractions prepared from rat brain cortex. Enzymatic activity was determined by measuring cAMP production with an HPLC technique. It was shown that 5-HT stimulates adenylate cyclase activity with 2 activation constants (Kact): one shows a high apparent affinity (Kact = 0.8 nM) and the other a lower apparent affinity (Kact = 0.30 microM). The latter activity, induced by micromolar concentrations of 5-HT, was inhibited by spiperone at concentrations that block 5-HT1A binding. 5-Methoxytryptamine, bufotenin, and LSD also had a stimulatory biphasic effect on adenylate cyclase activity, whereas trifluoromethylphenylpiperazine, 5-carboxyamidotryptamine, 8-hydroxy-(2-di-n-propylamino)tetralin, RU 24969 had a monophasic effect. Enzyme activation by drugs acting in the micromolar range was inhibited by spiperone (1 microM), suggesting a link between this activation and 5-HT1A sites. On the other hand, the high-affinity activation of the enzyme induced by 5-HT, 5-methoxytryptamine, bufotenin, LSD, and the activation induced by TFMPP were not inhibited by spiperone (1 microM), by propranolol (3 microM), or by mesulergine (0.1 microM), which selectively block 5-HT1A, 5-HT1B, and 5-HT1C sites. Inhibition was produced by dihydroergotamine, methysergide, cinanserin, and mianserin, but not by naloxone, phenoxybenzamine, and phentolamine. Therefore, these activations seem related to 5-HT1 receptors but not to 5-HT1A, 5-HT1B, or 5-HT1C sites. Accordingly, binding of [3H]5-HT to 5-HT1-like sites was examined in the presence of spiperone (1 microM) and propranolol (3 microM); in these conditions, a high-affinity site (KD = 3.4 nM) was indeed revealed. The relative potencies of a series of drugs that stimulate or inhibit the activation of the adenylate cyclase with a high affinity and their ability to inhibit this binding of [3H]5-HT showed a positive correlation, strongly suggesting a direct relation between this recognition site for 5-HT and the production of a second messenger (cAMP). Moreover, this potential receptor is shown to be heterogeneously distributed within the brain, and was localized postsynaptically at serotonergic synapses.
5-HT1型5-羟色胺结合位点具有异质性，似乎包含几种亚型（5-HT1A、5-HT1B和5-HT1C）；它们的生理作用尚不清楚。已在从大鼠脑皮质制备的膜组分中研究了5-羟色胺诱导的腺苷酸环化酶的刺激作用。通过用高效液相色谱技术测量环磷酸腺苷（cAMP）的产生来确定酶活性。结果表明，5-羟色胺以2个激活常数（Kact）刺激腺苷酸环化酶活性：一个显示出高表观亲和力（Kact = 0.8 nM），另一个显示出较低的表观亲和力（Kact = 0.30 microM）。由微摩尔浓度的5-羟色胺诱导的后一种活性，在阻断5-HT1A结合的浓度下被螺哌隆抑制。5-甲氧基色胺、蟾蜍色胺和麦角酸二乙胺对腺苷酸环化酶活性也有刺激的双相作用，而三氟甲基苯基哌嗪、5-羧酰胺色胺、8-羟基-（2-二正丙基氨基）四氢萘、RU 24969有单相作用。作用于微摩尔范围的药物引起的酶激活被螺哌隆（1 microM）抑制，提示这种激活与5-HT1A位点之间存在联系。另一方面，5-羟色胺、5-甲氧基色胺、蟾蜍色胺、麦角酸二乙胺诱导的酶的高亲和力激活以及三氟甲基苯基哌嗪诱导的激活，不受螺哌隆（1 microM）、普萘洛尔（3 microM）或美舒麦角（0.1 microM）的抑制，它们分别选择性阻断5-HT1A、5-HT1B和5-HT1C位点。二氢麦角胺、甲基麦角新碱、辛那色林和米安色林产生抑制作用，但纳洛酮、酚苄明和酚妥拉明则无此作用。因此，这些激活似乎与5-HT1受体有关，但与5-HT1A、5-HT1B或5-HT1C位点无关。相应地，在存在螺哌隆（1 microM）和普萘洛尔（3 microM）的情况下，检测了[3H]5-羟色胺与类5-HT1位点的结合；在这些条件下，确实揭示了一个高亲和力位点（KD = 3.4 nM）。一系列以高亲和力刺激或抑制腺苷酸环化酶激活的药物的相对效价及其抑制[3H]5-羟色胺这种结合的能力呈正相关，强烈提示5-羟色胺的这个识别位点与第二信使（cAMP）的产生之间存在直接关系。此外，这种潜在受体在脑内呈异质性分布，且位于5-羟色胺能突触的突触后部位。
