Acetylcholinesterase activity, and neurofilament protein, and catecholamine synthesizing enzymes immunoreactivities in the mouse adrenal gland during postnatal development.

The present study showed the acetylcholinesterase (AChE) activity, and neurofilament protein (NFP), catecholamine-synthesizing enzymes, dopamine beta-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) immunoreactivities in the mouse adrenal gland during postnatal development. From birth to postnatal-1-day, AChE activity was weakly and diffusely found in some medullary cells and in very few nerve fibers whereas strong NFP immunoreactivity was seen in a few ganglion cells and in remarkably numerous nerve fibers in the medulla. Almost all meduallary cells were reactive for both DBH and PNMT during this period. From postnatal-2- or -3-day to postnatal-1-week, strong AChE activity was observed in a few large ganglion cells, but the reaction was weak in clusters of chromaffin cells, and the number of strong AChE-active nerve fibers in the medulla was rapidly increased. From postnatal-2-day onwards, the number of NFP-immunoreactive nerve fibers in the medulla were remarkably numerous. Numerous chromaffin cells were reactive for both DBH and PNMT whereas some chromaffin cells were reactive for only DBH from postnatal-2-day onwards. These results suggest that drastic changes such as an increase of acetylcholine in the nerve fibers, differentiation of noradrenaline and adrenaline cells of the medulla may occur during this period. From postnatal-2-week to postnatal-3-week, weak AChE activity was seen in the clusters of several chromaffin cells and a few ganglion cells, and the number of AChE-active nerve fibers in the medulla was gradually increased. From postnatal-4-week to postnatal-8-week (adult), the distribution and frequency of AChE activity in the adrenal gland were similar to those at postnatal-3-week. In the adult, AChE activity was weakly seen in the clusters of several chromaffin cells showing noradrenaline fluorescence in the adrenal medulla. The noradrenaline cells were contacted by denser AChE-reactive nerve fibers than adrenaline cells. These results suggest that the development of cholinergic nervous system in the mouse adrenal medulla may be completed by postnatal-3-week.