Sun Y D, Benishin C G
Department of Physiology, University of Alberta Faculty of Medicine, Edmonton, Canada.
Eur J Pharmacol. 1994 Dec 27;271(2-3):453-9. doi: 10.1016/0014-2999(94)90806-0.
The plexus-free longitudinal muscle was used to investigate the muscle-relaxing effects of the known K+ channel openers, cromakalim, pinacidil and nicorandil, and compared with other known muscle relaxants, calcitonin gene-related peptide (CGRP) and isoprenaline. The three K+ channel openers all decreased basal tension and inhibited the tonic tension evoked by 30 mM KCl, 0.5 microM histamine or 0.1 microM oxotremorine in a dose-dependent manner. The order of potency is cromakalim > pinacidil > nicorandil in KCl or oxotremorine-precontracted muscle strip and nicorandil > cromakalim > pinacidil in histamine-precontracted muscle strip. Inhibition by cromakalim was completely reversed by glibenclamide, a blocker of ATP-sensitive K+ channels, while inhibition by nicorandil or pinacidil was only partially antagonized. The tonic tension evoked by KCl, histamine or oxotremorine was relaxed by CGRP or isoprenaline. Inhibition by neither of these compounds was relieved by glibenclamide. These results suggest that while ATP-sensitive K+ channels may be present in the longitudinal muscle cells, they may not be involved in the actions of CGRP or isoprenaline on the longitudinal muscle.
采用无丛状结构的纵行肌来研究已知的钾通道开放剂克罗卡林、吡那地尔和尼可地尔的肌肉松弛作用，并与其他已知的肌肉松弛剂降钙素基因相关肽（CGRP）和异丙肾上腺素进行比较。这三种钾通道开放剂均能降低基础张力，并以剂量依赖的方式抑制由30 mM氯化钾、0.5 microM组胺或0.1 microM氧化震颤素诱发的强直张力。在氯化钾或氧化震颤素预收缩的肌条中，效力顺序为克罗卡林>吡那地尔>尼可地尔；在组胺预收缩的肌条中，效力顺序为尼可地尔>克罗卡林>吡那地尔。ATP敏感性钾通道阻滞剂格列本脲可完全逆转克罗卡林的抑制作用，而尼可地尔或吡那地尔的抑制作用仅被部分拮抗。CGRP或异丙肾上腺素可松弛由氯化钾、组胺或氧化震颤素诱发的强直张力。格列本脲不能解除这两种化合物的抑制作用。这些结果表明，虽然纵行肌细胞中可能存在ATP敏感性钾通道，但它们可能不参与CGRP或异丙肾上腺素对纵行肌的作用。
