Effects of Serotonin and Nitric Oxide on Mid-gut Motility in Tobacco Hornworm (Manduca sexta) Larvae
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The anterior mid-gut of the tobacco hornworm, Manduca sexta, is active in mixing freshly ingested diet with gut secretion. Spontaneous muscle activity is lost when the anterior gut is isolated, suggesting that neural and/or humoral inputs may be important in sustaining normal activity in vivo. In preliminary studies, both serotonin and cGMP (the putative second messenger for NO) were visualized in the anterior mid-gut by immunohistochemistry. We have also shown that serotonin and sodium nitroprusside (SNP), a NO donor, have measurable effects on the contractile state of isolated anterior gut. In these studies both serotonin and SNP caused a long-lasting contraction of longitudinal and circular muscle mounts.