Hammond J R, MacDonald W F, White T D
Department of Pharmacology, Dalhousie University, Halifax, N.S., Canada.
Can J Physiol Pharmacol. 1988 Apr;66(4):369-75. doi: 10.1139/y88-062.
Neuronal varicosities, isolated from the myenteric plexus of guinea pig ileum longitudinal muscle, were incubated with [3H]noradrenaline to label the contents of the noradrenergic secretory vesicles. Exposure of these varicosities to KCl, nicotine, or acetylcholine resulted in the Ca2+ -dependent release of [3H]noradrenaline. Veratridine also evoked a large efflux of [3H] from this preparation, but this release was only partially Ca2+ dependent. The alpha 2-adrenoceptor agonist, clonidine, inhibited the K+-, nicotine-, and acetylcholine-induced release of [3H]noradrenaline. Similarly, exogenously administered (-)noradrenaline was an effective inhibitor of the K+ -evoked release of [3H]noradrenaline. The alpha 2-adrenoceptor antagonist, yohimbine, antagonized the inhibitory actions of both clonidine and (-)noradrenaline on the K+ -evoked release of [3H]noradrenaline from myenteric varicosities. Nicotine, acetylcholine, KCl, and veratridine also released ATP from these guinea pig ileal myenteric varicosities. However, the evoked release of ATP was unaffected by clonidine. These results indicate that myenteric varicosities can take up and release [3H]noradrenaline and that they possess presynaptic alpha 2-adrenoceptors which, when activated, inhibit the release of [3H]noradrenaline. These receptors may play a role in modulating the release of noradrenaline in the myenteric plexus in vivo. In addition, the present results suggest that ATP and [3H]noradrenaline may not be released from the same population of secretory vesicles in neuronal varicosities isolated from guinea pig ileum longitudinal muscle.
从豚鼠回肠纵肌肌间神经丛分离出的神经元膨体，与[3H]去甲肾上腺素一起孵育，以标记去甲肾上腺素能分泌囊泡的内容物。将这些膨体暴露于氯化钾、尼古丁或乙酰胆碱会导致[3H]去甲肾上腺素的钙依赖性释放。藜芦碱也能引起该制剂中大量的[3H]外流，但这种释放仅部分依赖于钙。α2-肾上腺素能受体激动剂可乐定可抑制钾离子、尼古丁和乙酰胆碱诱导的[3H]去甲肾上腺素释放。同样，外源性给予的（-）去甲肾上腺素是钾离子诱发的[3H]去甲肾上腺素释放的有效抑制剂。α2-肾上腺素能受体拮抗剂育亨宾可拮抗可乐定和（-）去甲肾上腺素对肌间膨体中钾离子诱发的[3H]去甲肾上腺素释放的抑制作用。尼古丁、乙酰胆碱、氯化钾和藜芦碱也能从这些豚鼠回肠肌间膨体中释放ATP。然而，诱发的ATP释放不受可乐定的影响。这些结果表明，肌间膨体能够摄取和释放[3H]去甲肾上腺素，并且它们具有突触前α2-肾上腺素能受体，该受体激活后可抑制[3H]去甲肾上腺素的释放。这些受体可能在体内调节肌间神经丛中去甲肾上腺素的释放中发挥作用。此外，目前的结果表明，ATP和[3H]去甲肾上腺素可能并非从豚鼠回肠纵肌分离出的神经元膨体中的同一群分泌囊泡中释放。
