Comparative study on the small intestinal motility of the juvenile and adult axolotl, Ambystoma mexicanum

The effects of four representative neuroendocrine substances, namely, carbamylcholine (CARB), noradrenalin (NAD), substance P (SP) and somatostatin (SS) on the in vitro small intestinal motility of juvenile and adult stages of the axolotl, Ambystoma mexicanum, were investigated. Both SP and CARB caused significant dose-dependent increases in contractility (affecting active and/or basal tone) which was more pronounced in case of SP. While NAD had significant dose-dependent inhibitory effects on the active tone, the weak effects of SS did not allow a firm conclusion regarding its possible involvement in control of the small intestinal motility. Split data analysis for each investigated neuroendocrine substance revealed that the juvenile small intestinal segments responded significantly different from their adult counterparts. Similarly, the significance of the data showed dependency on the investigated region of the small intestine. Interestingly, the proximal segments showed more significant responses to the excitatory effect provoked by SP and CARB than the distal segments. However, the latter showed more sensitivity to the inhibitory effects caused by NAD and SS. The overall effects exhibited a dose-dependent response with no significant influence for the lower concentrations on either active or basal tone.