Reinnervation of pancreatic tissue and islet grafts by aminergic, cholinergic and peptidergic nerves. A review

A brief history of the discovery of insulin and pancreatic tissue transplantation was given including the events that led to the introduction of pancreatic transplantation. This was followed by a detailed account of the different sites used in pancreatic tissue fragment and islet transplantation, and the fate of the grafts. Reinnervation of these pancreatic islet and tissue grafts have received little attention since pancreatic transplantation started in 1892 and it became apparent that only a couple of investigators have actually embarked on the systemic studies of the presence of different neurotransmitters and neuromodulators in the nerves reinnervating pancreatic islets and or fragments transplanted into different sites in the mammalian body. The nerves reinnervating pancreatic tissue and islets can be grouped into intrinsic or extrinsic nerves. The intrinsic nerves are the intrapancreatic neurons that survived and produced or stored neurotransmitters after transplantation. The extrinsic nerves are novel to the transplant and originate from the mixed nerve plexuses of the site of transplantation. These extrinsic nerves are carried into the transplant by the blood vessels revascularizing the pancreatic islet or tissue graft. The pattern of reinnervation by extrinsic nerves is depicted in diagrams.