Nassar C F, Barada K A, Abdallah L E, Hamdan W S, Taha A M, Atweh S F, Saadé N E
Department of Physiology, Faculty of Medicine, American University of Beirut, Lebanon.
Am J Physiol. 1995 Apr;268(4 Pt 1):G695-9. doi: 10.1152/ajpgi.1995.268.4.G695.
Capsaicin-sensitive primary afferent fibers (CSPA) in the small intestine regulate many functions through the release of peptides and neurotransmitters. This study was undertaken to assess the role of CSPA in the regulation of jejunal alanine absorption in the rat. In a series of in vivo experiments, the effects of the sensory neurotoxin capsaicin on small intestinal alanine absorption were evaluated. In vitro experiments were also done to study its effects on alanine uptake by isolated jejunal strips and mucosal scrapings. Jejunal alanine absorption was reduced by 27% when capsaicin (160 and 800 microM) was perfused intraluminally and by 21% when it was applied topically to the cervical vagi. On the other hand, bilateral cervical vagotomy and reversible block of vagal CSPA increased alanine absorption by 29 and 41%, respectively. In vitro, capsaicin reduced alanine uptake by intestinal strips in a dose-dependent manner. Maximal inhibition (36.5%) occurred at 400 microM with the mean ineffective concentration at 87 microM. Alanine uptake by jejunal mucosal scrapings, however, was decreased only by 6.7% when incubated with 1,600 microM capsaicin. These data suggest that vagal CSPA exerts a tonic inhibitory effect on alanine absorption and that capsaicin's inhibitory effect on alanine absorption is mediated largely by the capsaicin-sensitive afferent fibers.
小肠中的辣椒素敏感初级传入纤维（CSPA）通过释放肽类和神经递质来调节多种功能。本研究旨在评估CSPA在调节大鼠空肠丙氨酸吸收中的作用。在一系列体内实验中，评估了感觉神经毒素辣椒素对小肠丙氨酸吸收的影响。还进行了体外实验，以研究其对分离的空肠条和黏膜刮片摄取丙氨酸的影响。当腔内灌注辣椒素（160和800微摩尔）时，空肠丙氨酸吸收减少27%，当局部应用于颈迷走神经时减少21%。另一方面，双侧颈迷走神经切断术和迷走神经CSPA的可逆性阻断分别使丙氨酸吸收增加29%和41%。在体外，辣椒素以剂量依赖的方式降低肠条对丙氨酸的摄取。在400微摩尔时出现最大抑制（36.5%），平均无效浓度为87微摩尔。然而，当与1600微摩尔辣椒素一起孵育时，空肠黏膜刮片对丙氨酸的摄取仅减少6.7%。这些数据表明，迷走神经CSPA对丙氨酸吸收具有紧张性抑制作用，辣椒素对丙氨酸吸收的抑制作用主要由辣椒素敏感传入纤维介导。
