Preganglionic innervation of the pancreas islet cells in the rat.

The position and number of preganglionic somata innervating the insulin-secreting beta-cells of the endocrine pancreas were investigated in Wistar rats. This question was approached by comparing the innervation of the pancreas of normal rats with the innervation of the pancreas in alloxan-induced diabetic animals. The presumption was made that alloxan treatment destroys the beta-cells of the islet of Langerhans and results in a selective degeneration of the beta-cells innervation. Cell bodies of preganglionic fibers innervating the pancreas were identified by retrograde transport of horseradish peroxidase following pancreas injections. It was found that 25% of the cells innervating the pancreas in the left dorsal vagal motor nucleus, 50% of the cells in the ambiguous nucleus and 50% of the cells innervating the pancreas, that originate in segments C3-C4 of the spinal cord, fail to become labeled after alloxan treatment. The position and distribution of these cell groups are described in detail and are assumed to be involved in preganglionic beta-cell innervation. A second cell population in the ventral horn and intermediolateral column of the segments T3-L2 of the cord also was labeled in normal rats and was not affected by the alloxan treatment. These thoracic cell groups are thus considered as sympathetic preganglionic somata that maintain direct connections to the pancreas. Additional preliminary information is presented dealing with the general aspects of sympathetic and parasympathetic organization of the pancreas innervation.