Figure 1.

Three autonomic inputs to the islet alpha cell. Preganglionic sympathetic nerves travel in the spinal cord releasing ACh from their terminals within the celiac ganglion. The released ACh activates postganglionic sympathetic neuronal cell bodies whose fibers innervate the islet alpha cells and release norepinephrine. Preganglionic parasympathetic nerves travel in the vagus releasing ACh from their terminals within intrapancreatic parasympathetic ganglia. The released ACh activates postganglionic parasympathetic neuronal cell bodies, whose fibers innervate the islet alpha cells and release ACh. Preganglionic sympathetic nerves travel in the spinal cord releasing ACh from their terminals within the adrenal medulla. The released ACh activates the chromaffin cells to release of the sympathetic neurohormone epinephrine, which reaches the alpha cell via the arterial circulation. EPI, epinephrine; NE, norepinephrine.