Kagstrom J, Olsson C, Axelsson M, Franklin C E
Department of Zoophysiology, Goteborg University, S-413 90 Goteborg, Sweden.
Am J Physiol. 1998 Jun;274(6):R1740-50. doi: 10.1152/ajpregu.1998.274.6.R1740.
Peptidergic mechanisms influencing the resistance of the gastrointestinal vascular bed of the estuarine crocodile, Crocodylus porosus, were investigated. The gut was perfused in situ via the mesenteric and the celiac arteries, and the effects of different neuropeptides were tested using bolus injections. Effects on vascular resistance were recorded as changes in inflow pressures. Peptides found in sensory neurons [substance P, neurokinin A, and calcitonin gene-related peptide (CGRP)] all caused significant relaxation of the celiac vascular bed, as did vasoactive intestinal polypeptide (VIP), another well-known vasodilator. Except for VIP, the peptides also induced transitory gut contractions. Somatostatin and neuropeptide Y (NPY), which coexist in adrenergic neurons of the C. porosus, induced vasoconstriction in the celiac vascular bed without affecting the gut motility. Galanin caused vasoconstriction and occasionally activated the gut wall. To elucidate direct effects on individual vessels, the different peptides were tested on isolated ring preparations of the mesenteric and celiac arteries. Only CGRP and VIP relaxed the epinephrine-precontracted celiac artery, whereas the effects on the mesenteric artery were variable. Somatostatin and NPY did not affect the resting tonus of these vessels, but somatostatin potentiated the epinephrine-induced contraction of the celiac artery. Immunohistochemistry revealed the existence and localization of the above-mentioned peptides in nerve fibers innervating vessels of different sizes in the gut region. These data support the hypothesis of an important role for neuropeptides in the control of the vascular bed of the gastrointestinal tract in C. porosus.
研究了影响河口鳄（湾鳄）胃肠道血管床阻力的肽能机制。通过肠系膜动脉和腹腔动脉对原位肠道进行灌注，并使用推注法测试不同神经肽的作用。血管阻力的变化通过流入压力的改变来记录。在感觉神经元中发现的肽（P物质、神经激肽A和降钙素基因相关肽（CGRP））均引起腹腔血管床显著舒张，著名的血管舒张剂血管活性肠肽（VIP）也有同样作用。除VIP外，这些肽还诱导短暂的肠道收缩。在湾鳄的肾上腺素能神经元中共存的生长抑素和神经肽Y（NPY），可引起腹腔血管床血管收缩，但不影响肠道运动。甘丙肽引起血管收缩，偶尔还会激活肠壁。为阐明对单个血管的直接作用，对肠系膜动脉和腹腔动脉的离体环行标本进行了不同肽的测试。只有CGRP和VIP能使肾上腺素预收缩的腹腔动脉舒张，而对肠系膜动脉的作用则各不相同。生长抑素和NPY不影响这些血管的静息张力，但生长抑素可增强肾上腺素诱导的腹腔动脉收缩。免疫组织化学揭示了上述肽在支配肠道区域不同大小血管的神经纤维中的存在和定位。这些数据支持了神经肽在控制湾鳄胃肠道血管床中起重要作用这一假说。
