ISSN 2320-5407 International Journal of Advanced Research (2014), Volume 2, Issue 12, 92-104 Journal homepage: http://www.journalijar.com INTERNATIONAL JOURNAL OF ADVANCED RESEARCH RESEARCH ARTICLE Comparative study on the small intestinal motility of the juvenile and adult axolotl, Ambystoma mexicanum Gamal Badawy  Department of Zoology, Faculty of Science, Menoufiya University, Shebeen El-Koom, Egypt. Manuscript Info Abstract Manuscript History: Received: 15 October 2014 Final Accepted: 22 November 2014 Published Online: December 2014 Key words: Anatomy; Intestinal motility; Carbamylcholine;  Copy Right, IJAR, 2014,. All rights reserved Introduction The transport of food materials within the intestine depends on the activity of the gastrointestinal smooth muscle which performs a co-ordinated pattern of motor behaviour called peristalsis (Olsson and Holmgren, 2011). The latter is in principle similar in different vertebrate groups and consists of a dual reflex resulting in contraction above and relaxation below the site of stimulation (Kunze and Furness, 1999). Ascending (orally directed) excitatory and descending (anally directed) inhibitory reflexes are usually trigged by mucosal contact or radial distension of the intestine by its contents and thus occur after feeding. The intestinal smooth muscle is largely regulated by the autonomic nervous system via hormones and other biologically active substances in order to perform these reflexes effectively (Shuttleworth and Keef, 1995; Olsson and Holmgren, 2001; Olsson and Holmgren, 2011). Both hormones and the biologically active substances are secreted into the blood from either the mucosal endocrine cells located in the intestinal mucosa or enteric nerve fibres in response to specific components of the chyme, and delivered to the intestinal smooth muscle via blood circulation (Furness and Costa, 1987). Motor activity of the intestine is under the control of neuronal and hormonal mechanisms (Fujimiya and Inui, 2000). Nerves, hormones and smooth muscle act together in harmony to exert a co-ordinated control over intestinal function, which enables it to perform the different patterns of motility, accounted for at different stages of food processing. It is generally believed that the control of intestinal motility is regulated by the myenteric neurons and that the submucosal neurons are concerned mainly with the modulation of intestinal blood flow and ion transport (Surprenant, 1994). Isolated segments of the intestine can properly co-ordinate excitatory and inhibitory …………….. 92 Noradrenalin; Peptides; neurotransmitters *Corresponding Author Gamal Badawy, Gamalbadawy940@yahoo.com 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 were 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.