Vanner S, MacNaughton W K
Department of Physiology, Queen's University, Kingston, Ontario, Canada.
Am J Physiol. 1995 Aug;269(2 Pt 1):G203-9. doi: 10.1152/ajpgi.1995.269.2.G203.
This study examined whether capsaicin-sensitive sensory nerves regulate intestinal ion transport using both Ussing chamber and intracellular recording techniques in in vitro submucosal preparations from the guinea pig ileum. In Ussing chamber studies, serosal application of capsaicin (20 nM-20 microM) evoked a biphasic dose-dependent increase in short-circuit current (Isc) (maximal effective concentration 200 nM and 2 microM, respectively). In chloride-free buffer, capsaicin responses were significantly reduced. Capsaicin evoked little or no response when extrinsic sensory nerve fibers had been surgically removed and tetrodotoxin and low-calcium and high-magnesium solutions blocked responses to capsaicin. In epithelial preparations devoid of submucosal neurons, capsaicin had virtually no effect, suggesting that responses evoked by capsaicin-sensitive nerves result from activation of submucosal secretomotor neurons. Intracellular recordings from single submucosal neurons demonstrated that superfusion with capsaicin (2 microM) depolarized neurons with an associated decreased conductance. Depolarizations were completely desensitized when capsaicin was reapplied, but synaptic inputs were unaffected. This study suggests that capsaicin-sensitive nerves can regulate ion transport in the gastrointestinal tract by release of neurotransmitter(s) that activate submucosal secretomotor neurons.
本研究利用乌斯电极槽和细胞内记录技术，在豚鼠回肠体外黏膜下制备物中，研究了辣椒素敏感感觉神经是否调节肠道离子转运。在乌斯电极槽研究中，向浆膜施加辣椒素（20 nM - 20 μM）可引起短路电流（Isc）呈双相剂量依赖性增加（最大有效浓度分别为200 nM和2 μM）。在无氯缓冲液中，辣椒素反应显著降低。当手术切除外在感觉神经纤维，且河豚毒素以及低钙高镁溶液阻断对辣椒素的反应时，辣椒素引起的反应很小或无反应。在没有黏膜下神经元的上皮制备物中，辣椒素几乎没有作用，这表明辣椒素敏感神经引起的反应是由黏膜下分泌运动神经元的激活所致。对单个黏膜下神经元的细胞内记录显示，用辣椒素（2 μM）进行灌流可使神经元去极化，同时伴随电导降低。当再次施加辣椒素时，去极化完全脱敏，但突触输入不受影响。本研究表明，辣椒素敏感神经可通过释放激活黏膜下分泌运动神经元的神经递质来调节胃肠道中的离子转运。
