Role of capsaicin-sensitive afferent neurons in receptive relaxation induced by gastric distension in rats |
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Authors: | M Taniguchi Y Mashita Y Matsuzaka S Kato K Takeuchi |
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Institution: | (1) Department of Pharmacology and Experimental Therapeutics, Kyoto Pharmaceutical University, Misasagi, Yamashina, Kyoto 607-8414, Japan |
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Abstract: | We investigated the role of capsaicin-sensitive afferent neurons in receptive relaxation of the rat stomach in response to
distension. Under urethane anesthesia, a balloon with barostat was inserted through the pylorus and placed in the forestomach.
Isobaric distension was performed in a stepwise increment of 2 mmHg, each lasting for 2 min, while the corresponding intragastric
volume was recorded. Gastric distension produced the intraballoon volume in a progressive manner with saturation, suggesting
the occurrence of receptive relaxation of the stomach during distension. Intragastric application of capsaicin significantly
enhanced the degree of receptive relaxation. The capsaicin-induced enhancement of receptive relaxation was totally abolished
by bilateral vagotomy as well as chemical ablation of capsaicin-sensitive afferent neurons. Likewise, the enhanced receptive
relaxation in response to stomach distension was also significantly attenuated by pretreatment of the animals with NG-nitro-L-arginine methyl ester (L-NAME, an inhibitor of nitric oxide (NO) synthase), calcitonin gene related peptide (CGRP)8-37 (CGRP antagonist), indomethacin and ONO-8711 (EP1 receptor antagonist). These results suggest that capsaicin significantly
enhanced the receptive relaxation induced by gastric distention through both vagal nerves and capsaicin-sensitive afferent
neurons. This process is intervened by endogenous NO and CGRP in addition to prostaglandins (PGs), and the effect of PGs may
be mediated by EP1 receptors.
Received 9 October 2006; accepted 10 November 2006 |
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Keywords: | Receptive relaxation Capsaicin Afferent neurons Nitric oxide (NO) Prostaglandins (PGs) Calcitonin gene-related peptide (CGPR) |
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