Montpetit C J, Perry S F
Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, Ontario K1N 6N5, Canada.
J Endocrinol. 2000 Sep;166(3):705-14. doi: 10.1677/joe.0.1660705.
The aim of the present investigation was to assess the relative contributions of cholinergic (acetylcholine) and non-cholinergic vasoactive intestinal polypeptide (VIP), and pituitary adenylate cyclase activating polypeptide (PACAP) neurotransmitters in the neuronal control of catecholamine secretion from the chromaffin tissue lining the posterior cardinal vein of the rainbow trout (Oncorhynchus mykiss). Using an in situ saline-perfused posterior cardinal vein preparation, it was demonstrated that exogenous administration of chicken VIP or human PACAP-27 caused a dose-dependent increase in adrenaline secretion; noradrenaline secretion was unaffected. Analysis of dose-response curves indicated that VIP and PACAP stimulated the secretion of adrenaline with a similar degree of potency (ED(50) for VIP=1.90x10(-11) mol/kg; ED(50) for PACAP=1.03x10(-11) mol/kg). The VIP/PACAP-elicited secretion was diminished in the presence of the VIP receptor antagonist, VIP 6-28, but was unaffected by the PACAP receptor antagonist, PACAP 6-27, or the cholinergic antagonists, hexamethonium and atropine. Thus, this is the first study to demonstrate a direct stimulatory role for VIP or PACAP in catecholamine secretion from piscine chromaffin cells. The relative contribution of cholinergic and non-cholinergic neurotransmitters in the neuronal control of catecholamine secretion from the chromaffin tissue was evaluated using an in situ nerve-stimulating technique previously validated by us in the rainbow trout. This was accomplished by comparing catecholamine secretion in the presence or absence of cholinergic and the VIP and PACAP receptor antagonists during different levels of electrical stimulation. The results demonstrated that cholinergic stimulation predominated during high frequency of electrical stimulation (20 Hz) while the non-cholinergic component prevailed at low frequency (1 Hz). Overall, the results of the present investigation demonstrate that VIP and/or PACAP may directly stimulate adrenaline secretion from trout chromaffin cells at low levels of neuronal activity. Therefore, the neuronal control of catecholamine secretion in teleosts may not be confined to cholinergic-evoked events.
本研究的目的是评估胆碱能（乙酰胆碱）和非胆碱能血管活性肠肽（VIP）以及垂体腺苷酸环化酶激活肽（PACAP）神经递质在虹鳟（Oncorhynchus mykiss）后主静脉内衬嗜铬组织儿茶酚胺分泌的神经控制中的相对贡献。使用原位生理盐水灌注后主静脉制备方法，结果表明，外源性给予鸡VIP或人PACAP - 27会导致肾上腺素分泌呈剂量依赖性增加；去甲肾上腺素分泌不受影响。剂量反应曲线分析表明，VIP和PACAP刺激肾上腺素分泌的效力相似（VIP的ED(50)=1.90×10(-11) mol/kg；PACAP的ED(50)=1.03×10(-11) mol/kg）。在存在VIP受体拮抗剂VIP 6 - 28的情况下，VIP/PACAP引发的分泌减少，但不受PACAP受体拮抗剂PACAP 6 - 27或胆碱能拮抗剂六甲铵和阿托品的影响。因此，这是第一项证明VIP或PACAP在鱼类嗜铬细胞儿茶酚胺分泌中具有直接刺激作用的研究。使用我们之前在虹鳟中验证过的原位神经刺激技术，评估了胆碱能和非胆碱能神经递质在嗜铬组织儿茶酚胺分泌的神经控制中的相对贡献。这是通过比较在不同电刺激水平下存在或不存在胆碱能、VIP和PACAP受体拮抗剂时的儿茶酚胺分泌来实现的。结果表明，在高频电刺激（20 Hz）时胆碱能刺激占主导，而在低频（1 Hz）时非胆碱能成分占优势。总体而言，本研究结果表明，在低水平神经元活动时，VIP和/或PACAP可能直接刺激鳟鱼嗜铬细胞分泌肾上腺素。因此，硬骨鱼中儿茶酚胺分泌的神经控制可能不限于胆碱能诱发的事件。
