Jin J G, Takaki M, Nakayama S
Department of Physiology, Okayama University Medical School, Japan.
Eur J Pharmacol. 1990 May 3;180(1):13-9. doi: 10.1016/0014-2999(90)90587-v.
A segment of guinea-pig ileum, which was continuous with a strip of longitudinal muscle-myenteric plexus (LM-MP) at the anal end, was used to examine the effect of capsaicin on ascending excitatory pathways. Electrical field stimulation of the LM-MP caused an ascending contraction of the segment. After initially causing contraction capsaicin (3 microM) inhibited the ascending contraction. This inhibitory effect of capsaicin exhibited rapid desensitization and was abolished after extrinsic (mesenteric) denervation. Desensitization to calcitonin gene-related peptide (CGRP) prevented the capsaicin-induced inhibition without affecting the ascending contraction. Neither naloxone nor alpha- and beta-adrenoceptor antagonists affected the capsaicin-induced inhibition. CGRP (25 nM) also inhibited the ascending contraction, mimicking the inhibition induced by capsaicin. Ruthenium red (0.1-3 microM) antagonized the capsaicin-induced inhibition in a concentration-related manner, but did not affect the CGRP-induced inhibition. These findings suggest that the inhibitory effect of capsaicin on the ascending pathways might be mediated via the release of CGRP from extrinsic nerve terminals, and that the site of the antagonism of the action of capsaicin by ruthenium red is prejunctional.
一段豚鼠回肠，其在肛门端与一条纵行肌-肌间神经丛（LM-MP）相连，用于研究辣椒素对上行兴奋性通路的作用。对LM-MP进行电场刺激会引起该段回肠的上行收缩。在最初引起收缩后，辣椒素（3微摩尔）抑制了上行收缩。辣椒素的这种抑制作用表现出快速脱敏，并且在去交感神经（肠系膜）后被消除。对降钙素基因相关肽（CGRP）脱敏可防止辣椒素诱导的抑制，而不影响上行收缩。纳洛酮以及α和β肾上腺素能受体拮抗剂均不影响辣椒素诱导的抑制。CGRP（25纳摩尔）也抑制上行收缩，模拟了辣椒素诱导的抑制。钌红（0.1 - 3微摩尔）以浓度相关的方式拮抗辣椒素诱导的抑制，但不影响CGRP诱导的抑制。这些发现表明，辣椒素对上行通路的抑制作用可能是通过从交感神经末梢释放CGRP介导的，并且钌红对辣椒素作用的拮抗部位是节前的。
