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首页> 外文期刊>American Journal of Physiology >Mechanisms of mechanotransduction by specialized low-threshold mechanoreceptors in the guinea pig rectum.
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Mechanisms of mechanotransduction by specialized low-threshold mechanoreceptors in the guinea pig rectum.

机译：特殊的低阈值机械受体在豚鼠直肠中的机械传导机制。

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The guinea pig rectum, but not the colon, is innervated by a specialized class of distension-sensitive mechanoreceptors that have transduction sites corresponding to rectal intraganglionic laminar endings (rIGLEs). Rectal mechanoreceptors recorded in vitro had low threshold to circumferential stretch, adapted slowly, and could respond within 2 ms to mechanical stimulation by a piezo-electric probe. Antagonists to ionotropic N-methyl-D-aspartate (NMDA; CGS 19755, memantine) and non-NMDA (6,7-dinitroquinoxaline-2,3-dione) glutamate receptors did not affect mechanotransduction. In normal Krebs solution, the P2X purinoreceptor agonist alpha,beta-methylene ATP reduced mechanoreceptor firing evoked by distension but simultaneously relaxed circular smooth muscle and inhibited stretch-induced contractions. Neither ATP nor alpha,beta-methylene ATP affected mechanotransduction when transduction sites were directly compressed with von Frey hairs. The P2 purinoreceptor antagonist pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid did not affect stretch-induced firing but reduced the inhibitory effect of alpha,beta-methylene ATP on stretch-induced firing. Under isometric conditions, blocking synaptic transmission in Ca2+-free solution reduced stretch-evoked firing but not when basal tension was restored to control levels. Under isotonic condition, Ca2+-free solution did not significantly affect load-evoked firing. The blockers of mechanogated and/or transient receptor potential channels, benzamil, Gd3+, SKF 96365, and ruthenium red inhibited stretch-induced firing but, in parallel, significantly reduced stretch-induced contractions. Benzamil and SKF 96365 were able to inhibit mechanotransduction when transduction sites were compressed with von Frey hairs. The results show that mechanotransduction is rapid but does not depend on fast exocytotic release of mediators. It is likely that stretch-activated ion channels on rIGLEs are involved in direct, physical mechanotransduction by rectal low-threshold mechanoreceptors.
机译：豚鼠的直肠，而不是结肠，由一类特殊的对扩张敏感的机械感受器支配，这些感受器具有与直肠神经节内层状末端（rIGLE）相对应的转导位点。体外记录的直肠机械感受器对周向拉伸的阈值低，适应缓慢，并且可以在2 ms内对压电探针对机械刺激的反应。离子型N-甲基-D-天冬氨酸（NMDA; CGS 19755，美金刚）和非NMDA（6,7-二硝基喹喔啉-2,3-二酮）谷氨酸受体的拮抗剂不影响机械转导。在正常的Krebs溶液中，P2X嘌呤受体激动剂α，β-亚甲基ATP减少了因扩张引起的机械感受器放电，但同时放松了圆形平滑肌并抑制了拉伸诱导的收缩。当转导位点直接用冯·弗雷毛压缩时，ATP和α，β-亚甲基ATP都不会影响机械转导。 P2嘌呤受体拮抗剂磷酸吡ido醛-6-偶氮苯基-2'，4'-二磺酸不影响拉伸诱导的发射，但降低了α，β-亚甲基ATP对拉伸诱导的发射的抑制作用。在等距条件下，在无Ca2 +溶液中阻断突触传递可减少拉伸诱发的放电，但当基础张力恢复至控制水平时则不会。在等渗条件下，不含Ca2 +的溶液不会显着影响诱发负荷的烧成。机械化和/或瞬时受体电位通道的阻滞剂，苯扎米尔，Gd3 +，SKF 96365和钌红可抑制拉伸诱导的射击，但与此同时，可显着降低拉伸诱导的收缩。当转导位点被冯·弗雷毛压缩时，Benzamil和SKF 96365能够抑制机械转导。结果表明机械转导是快速的，但不依赖于介导的胞外快速释放。 rIGLE上的拉伸激活离子通道可能通过直肠低阈值机械感受器参与直接的物理机械传导。

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