Ordway G A, Boheler K R, Longhurst J C
Department of Physiology, University of Texas Health Science Center, Dallas 75235.
Am J Physiol. 1988 Feb;254(2 Pt 2):H354-60. doi: 10.1152/ajpheart.1988.254.2.H354.
Capsaicin and bradykinin stimulate afferents from certain viscera to reflexly activate the cardiovascular system; however, whether these agents evoke similar reflex responses when applied topically to the intestine is not known. Therefore, in cats anesthetized with methoxyflurane, we applied capsaicin (10 micrograms) or bradykinin (0.5 microgram) to the serosal surface of the jejunum. Additionally, we topically applied bethanechol chloride, a synthetic choline ester with little direct cardiovascular effects, to evoke marked contraction of the smooth muscle of the jejunum. Capsaicin evoked significant (P less than 0.05) increases in mean arterial pressure (105 +/- 4 to 119 +/- 4 mmHg, mean +/- SE), first derivative left ventricular pressure (dP/dt) at 40 mmHg (2,698 +/- 134 to 3,105 +/- 155 mmHg/s), systemic vascular resistance (0.63 +/- 0.15 to 0.68 +/- 0.15 peripheral resistance units), and heart rate (196 +/- 14 to 205 +/- 15 beats/min), whereas aortic flow did not change. In a dose-dependent fashion, bradykinin and bethanechol each caused cardiovascular activation as well as a marked contraction of the smooth muscle in the segment of jejunum to which they were applied. In contrast, capsaicin produced no detectable contraction of visceral smooth muscle. Removal of the celiac and superior mesenteric ganglia abolished the cardiovascular responses evoked by capsaicin and bradykinin. Thus, in cats, stimulating intestinal afferents by topically applying capsaicin or bradykinin reflexly activates the cardiovascular system. Furthermore, although mechanoreceptors may contribute to the responses evoked by bradykinin and bethanechol, the capsaicin-related responses likely are mediated exclusively by chemically sensitive receptors.
辣椒素和缓激肽可刺激某些内脏的传入神经，从而反射性地激活心血管系统；然而，当将这些药剂局部应用于肠道时，它们是否会引发类似的反射反应尚不清楚。因此，在用甲氧氟烷麻醉的猫中，我们将辣椒素（10微克）或缓激肽（0.5微克）应用于空肠的浆膜表面。此外，我们局部应用氯化贝胆碱，一种几乎没有直接心血管作用的合成胆碱酯，以引起空肠平滑肌的明显收缩。辣椒素使平均动脉压显著升高（P<0.05）（从105±4 mmHg升高至119±4 mmHg，平均值±标准误），左心室压力在40 mmHg时的一阶导数（dP/dt）（从2,698±134 mmHg/s升高至3,105±155 mmHg/s），全身血管阻力（从0.63±0.15外周阻力单位升高至0.68±0.15外周阻力单位），以及心率（从196±14次/分钟升高至205±15次/分钟），而主动脉血流量没有变化。缓激肽和氯化贝胆碱均以剂量依赖的方式引起心血管激活以及它们所应用的空肠段平滑肌的明显收缩。相比之下，辣椒素未引起内脏平滑肌的可检测到的收缩。切除腹腔神经节和肠系膜上神经节消除了辣椒素和缓激肽引起的心血管反应。因此，在猫中，通过局部应用辣椒素或缓激肽刺激肠道传入神经会反射性地激活心血管系统。此外，虽然机械感受器可能参与缓激肽和氯化贝胆碱引起的反应，但与辣椒素相关的反应可能仅由化学敏感感受器介导。
