VIPergic innervation of diabetic pancreas in rats.

Morphological, ultrastructural, and immunocytochemical studies of nerves containing vasoactive intestinal peptide (VIP) are described in diabetic pancreas of rats after streptozotocin treatment. The observations covered 48 hours and 6 months following streptozotocin treatment. At the ultrastructural level, degenerative changes were already observed in axons of nerve ganglia in the pancreas 48 hours (early stage) after streptozotocin treatment. These changes were hardly detected at the light microscopic level and VIP-like immunoreactivities were seen in nerves and fibers in such pancreas. The nerve ganglia were almost absent in the diabetic pancreas 6 months after streptozotocin treatment (late stage). Associated with the absence of nerve ganglia, nerves and fibers containing VIP-like immunoreactivities were also absent at this late stage. The findings indicated that the changes in the diabetic pancreas were neuropathic caused by metabolic disturbance after long standing diabetes and resulting absence of VIP-like immunoreactive nerves occurred. It was suggested from the present study that the changes in nerve ganglia began as damage at the ultrastructural level due to acute toxicity of the chemical at an early stage and then developed destruction and absence at a late stage.