Distribution of calcitonin-gene-related peptide, neuropeptide-Y, vasoactive intestinal polypeptide, cholecystokinin-8, substance P and islet peptides in the pancreas of normal and diabetic rats

Neuropeptides and peptides are particularly important in the co- ordination of pancreatic exocrine and endocrine secretions. In diabetes mellitus, pancreatic endocrine secretion is particularly impaired. This study investigates whether there is a change in the pattern of distribution of neuropeptides including calcitonin-gene-related peptide (CGRP), neuropeptide- Y (NPY), vasoactive intestinal polypeptide (VIP), cholecystokinin-octapeptide (CCK-8), substance P (SP), and islet peptides including insulin (INS), glucagon (GLU), somatostatin (SOM) and pancreatic polypeptide (PP) in the pancreas of streptozotocin (STZ)-diabetic rats. After the onset of diabetes, the pattern of distribution of INS, GLU, SOM and PP cells was deranged. CGRP was demonstrated in ganglion cells of both normal and diabetic pancreas. CGRP was also localized in nerve fibres innervating the blood vessels of both normal and diabetic pancreas. The pancreata of both normal and diabetic rats contained numerous NPY-immunopositive varicose nerve fibres in the wall of blood vessels. In normal pancreatic tissue, VIP-immunopositive nerve fibres were observed in all areas of the pancreas. After the onset of diabetes, VIP- positive nerve fibres were still discernible in the interacinar regions of the pancreas. CCK-8 was identified in nerve fibres innervating both the normal and diabetic rat pancreata. These CCK-8-immunopositive nerves were varicose in nature and distributed in the wall of blood vessels. SP was demonstrated in neurons located in the interlobular areas of normal tissue and in fine varicose nerve fibres of the interacinar region of STZ-induced diabetic pancreas. In conclusion, CGRP, NPY, VIP, CCK-8 and SP are well distributed in both normal and diabetic pancreas.