Morphological and functional aspects of pancreatic islet innervation

Pancreatic islets are collections of 4 functionally-related endocrine cells distributed nonrandomly in the pancreas. Their major physiological actions center about the regulation of metabolic homeostasis. Experimental evidence shows that, in addition to circulating substates, the islets are controlled by outflow from the central nervous system communicated through autonomic nerves. Islet cells also interact with one another via hormonal messengers and, possibly, electrotonic impulses producing a complex--yet well-controlled--system for the integration of numerous types of signals. This paper is a brief review of some of the numerous interactions between the autonomic nervous system and the endocrine pancreas. Particular emphasis is placed on the role of recently discovered autonomic factors and newly recognized autonomic centers in the brain.