LOCALIZATION OF GLUTAMATE-RECEPTOR SUBUNITS OF THE PHA-AMINO-3-HYDROXY-5-METHYL-4-ISOXAZOLEPROPIONATE (AMPA) TYPE IN THE PANCREAS OF NEWBORN GUINEA-PIGS

Glutamate and related molecules are the major excitatory neurotransmit ters in the, central nervous system, and their receptors have been loc alized therein. Little is, however, known about them in the peripheral nervous system. The present study investigated the localization of gl utamate receptor subunits of the pha-amino-3-hydroxy-5-methyl-4-isoxaz olepropionate (AMPA) type (GluR1, GluR2-3. and GluR4) in thr pancreas of newborn guinea pigs. With a double-labeling method of immunofluores cence and immuno-tetrahydrochloride reaction, GluR1 and GluR4 immunore activities were localized mostly in the insulin-secreting cells In the central mass of the islet, and GluR2-3 immunoreactivity in the periph eral rim of the islet, which consists mainly of non-insulin-secreting Islet cells. With a double-labeling method employing immunofluorescenc e and NADPH-diaphorase (NADPH-d) histochemistry, GluR2-3 and GluR4 imm unoreactivities were localized in most of the NADPH-d-positive pancrea tic ganglion cells. None or the NADPH-d-positive ganglion cells showed GluR1 immunoreactivity. In fact, GluR1 immunoreactivity was not detec ted in any of the pancreatic ganglion cells, The results indicate that glutamate is likely to exert its effects on the pancreas by activatin g different AMPA receptor subunits located in endocrine cells and intr apancreatic ganglia.