ISLET AMYLOID POLYPEPTIDE (AMYLIN) IS EXPRESSED IN SENSORY NEURONS

Islet amyloid polypeptide (IAPP) or amylin is a hormone candidate pred ominantly expressed in insulin cells. A role for IAPP in the regulatio n of glucose homeostasis and the development of non-insulin-dependent diabetes mellitus has been proposed. IAPP is structurally related to t he sensory neuropeptide calcitonin gene-related peptide. In the presen t study, using in situ hybridization, immunocytochemistry, and immunoc hemistry, the expression of IAPP in sensory neurons in the rat was inv estigated. IAPP was expressed in a population of small- to medium-size d nerve cell bodies in dorsal root ganglia from all levels and in the jugular-nodose and trigeminal ganglion; IAPP-expressing nerve cell bod ies constituted a subpopulation of those expressing calcitonin gene-re lated peptide. In addition, IAPP-like immunoreactivity occurred in ner ve cell bodies storing substance P and pituitary adenylate cyclase-act ivating polypeptide. IAPP-immunoreactive nerve fibers were encountered in the dorsal horns of the spinal cord, and to a lesser extent in per ipheral tissues receiving sensory innervation; IAPP-immunoreactive fib ers constituted a subpopulation of those containing calcitonin gene-re lated peptide and/or substance P. The immunochemical determinations de monstrated a low level of IAPP-like immunoreactivity in the dorsal roo t ganglia and spinal cord, which chromatographically coeluted with aut hentic rat IAPP. We conclude that IAPP is expressed in sensory neurons , thus being a novel sensory neuropeptide candidate for which a physio logical role remains to be identified.