Gamma‐aminobutyric acid B Receptor Immunoreactivity in the Mouse Adrenal Medulla

ABSTRACT The present study examined gamma‐aminobutyric acid B (GABAB) receptor, GABA, choline acetyltransferase (ChAT), and neuronal nitric oxide synthase (nNOS) immunoreactivities in the mouse adrenal medulla. GABAB receptor immunoreactivity was seen in numerous chromaffin cells and in a few ganglion cells of the adrenal medulla. By using a formaldehyde‐induced fluorescence (FIF) method, GABAB receptor immunoreactivity was observed in numerous adrenaline (A) cells, but not in noradrenaline (NA) cells showing blue‐white fluorescence. This suggests that GABAB receptors may be present in the A cells and be related to the secretory activity of A cells but not NA cells in the mouse adrenal medulla. GABAB receptor immunoreactive ganglion cells were shown to be nNOS immunopositive by using a double immunostaining method. Weak GABA immunoreactivity was visible in some chromaffin cells and in the numerous nerve fibers of the medulla. By using the FIF method, weak GABA‐immunoreactive chromaffin cells were shown to be in the NA cells showing blue‐white fluorescence. GABA‐immunoreactive nerve fibers were in dense contact in A cells, but not NA cells. GABA‐immunoreactive nerve fibers closely contacted a few ganglion cells. Numerous GABA‐immunoreactive nerve fibers in the medulla showed ChAT immunoreactive. This result suggests that GABA and acetylcholine may be released from the same nerve fibers and may have a secretory effect on the A cells of the medulla. Anat Rec, 296:971–978, 2013. © 2013 Wiley Periodicals, Inc.