RESUMO
Vasoactive intestinal peptide (VIP) belongs to a group of peptides with the same prohormone precursor found in nerves in a wide range of tissues, including the gastrointestinal tract (GIT). VIP is also found in the central nervous system and autonomic ganglia where they exist as neurotransmitters. In the gut VIP is found in the submucosal and myenteric plexus and it modulates gut motility, specifically it contracts the longitudinal and circular muscle fibres and relaxes the pyloric and lower esophageal sphincters. Hypersecretion of VIP has been reported to result in watery diarrhoea-hypokalaemia-hypochlorhydria (WDHH) syndrome, characterized by hyper motility and dehydration. VIP has also been implicated as one of the neurotransmitters involved in erection, and some VIP analogues have been successfully used in the management of erectile dysfunction in diabetics. The purpose of this study is to determine whether the VIP-producing neurons in the GIT contribute to the reported decrease in the level of VIP in diabetics. Alloxan diabetic rats, maintained in hyperglycemic state for 60 days were sacrificed and specimens from their stomach and intestines were stained immunohistochemically for VIP-secreting neurons. Results showed that the imunoreactivity of VIP-secreting neurons in the submucosa of the stomach and small intestine were significantly reduced in alloxan-diabetic Sprague Dawley rats when compared with control. This result suggests that VIP-producing neurons in the GIT may play a significant role in the reported reduced levels of VIP in diabetics, and implies that VIP secreted by these neurons may contribute , in a paracrine manner, to some of the motility complications associated with diabetes mellitus.
