Kumakura K, Karoum F, Guidotti A, Costa E
Nature. 1980 Jan 31;283(5746):489-92. doi: 10.1038/283489a0.
Morphological, physiological and pharmacological evidence indicates that opioid peptides, which in the brain are located intraneurally, may function as neurotransmitters. Similar evidence is not yet available for the opioid peptides that are stored in chromaffin cells of adrenal medulla and in axon terminals located in adrenal medulla and sympathetic ganglia. The present report contributes evidence suggesting that the opioid peptides which are stored in the axon terminals of the splanchnic nerves located in adrenal medulla may function as neuromodulators of the acetylcholine receptors located on chromaffin cells that are involved in catecholamine release. We support this functional role of the opioid peptides by showing that primary cultures of chromaffin cells of bovine medulla contain opiate receptors. When these receptors are occupied by specific agonists, the number of nicotinic receptors and the amount of catecholamine released by maximal doses of nicotine are reduced. Thus, like in other neuronal systems also in adrenal medulla, the action of opioid peptides is inhibitory. The specificity of this action is in part supported by the inability of opiate receptor agonists to reduce the Ca2+-dependent release of catecholamines elicited by K+ ions.
形态学、生理学及药理学证据表明，在大脑中位于神经内的阿片肽可能发挥神经递质的作用。然而，对于储存在肾上腺髓质嗜铬细胞以及位于肾上腺髓质和交感神经节的轴突终末中的阿片肽，目前尚未有类似的证据。本报告提供的证据表明，储存在位于肾上腺髓质的内脏神经轴突终末中的阿片肽，可能作为参与儿茶酚胺释放的嗜铬细胞上乙酰胆碱受体的神经调质发挥作用。我们通过证明牛髓质嗜铬细胞的原代培养物含有阿片受体，来支持阿片肽的这一功能作用。当这些受体被特异性激动剂占据时，烟碱受体的数量以及最大剂量尼古丁释放的儿茶酚胺量会减少。因此，与其他神经系统一样，在肾上腺髓质中阿片肽的作用也是抑制性的。阿片受体激动剂无法降低由钾离子引发的儿茶酚胺的钙离子依赖性释放，这在一定程度上支持了这种作用的特异性。
