γ-Aminobutyric acid B receptor immunoreactivity in the mouse adrenal medulla.

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.

Acetylcholinesterase activity, choline acetyltransferase and vesicular acetylcholine transporter immunoreactivities in the rat adrenal gland during postnatal development.

From postnatal-day-0 to postnatal-day-2, a few acetylcholinesterase (AChE)-active and choline acetytransferase (ChAT)-immunoreactive nerve fibers and relatively numerous vesicular acetylcholine transporter (VAChT)-immunoreactive puncta were observed in the rat adrenal medulla. Despite relatively numerous clear vesicles in the nerve fibers, the synthesis and hydrolysis of acetylcholine may not be fully activated until postnatal-day-2. The number of AChE-active and ChAT-immunoreactive nerve fibers dramatically increased and that of VAChT-immunoreactive puncta gradually increased from postnatal-day-3 to postnatal-week-1. The synthesis and hydrolysis of acetylcholine may be dramatically activated in the nerve fibers of the medulla until postnatal-week-1. From postnatal-week-2 to postnatal-week-3, the number of AChE-active and the ChAT-immunoreactive nerve fibers gradually increased and reached the adult levels. The VAChT-immunoreactive puncta per unit area was maximum number at postnatal-week-2. The synthesis and hydrolysis of acetylcholine in the nerve fibers of the medulla may be completed between postnatal-week-2 to postnatal-week-3. The diameter of the VAChT-immunoreactive puncta gradually increased from postnatal-day-0 with aging. However, the number of the VAChT-immunoreactive puncta gradually decreased from postnatal-week-2 onwards. In electron-microscopy, the VAChT-immunoreactive deposits were seen in clusters of clear vesicles, and the diameter of the nerve fibers and the number of clear vesicles at postnatal-week-8 increased compared with those at postnatal-week-2. The AChE-active, ChAT-immunoreactive, and VAChT-immunoreactive nerve fibers observed around noradrenaline (NA) cells were denser than those around adrenaline (A) cells in the medulla at postnatal-week-8. These suggest that the preferential innervation of NA and A cells may cause the differential secretion NA and A.

Neuropeptide Y- and catecholamine-synthesizing enzymes: immunoreactivities in the rat carotid body during postnatal development.

Immunocytochemical studies of the rat carotid body during postnatal development revealed neuropeptide Y (NPY), tyrosine hydroxylase (TH), and dopamine beta-hydroxylase (DBH) immunoreactivities. In adult rats (at postnatal week 10), NPY and DBH immunoreactivities were shown in a few small chief cells (cell number/section shown as mean +/- SD: NPY 3.4+/-2.6, DBH 3.2+/-2.3), in large ganglion cells, and in numerous varicose nerve fibers of the carotid body. TH immunoreactivity was found in almost all chief cells, in a few ganglion cells, and in numerous varicose nerve fibers in the carotid body. By using the double-immunostaining technique, most NPY-immunoreactive chief cells, ganglion cells, and nerve fibers exhibited DBH immunoreactivity. The NPY- and DBH-immunoreactive chief cells in the rat carotid body were numerous from birth (NPY 93.8+/-14.9, DBH 89.7+/-12.3) to postnatal week 1 (NPY 65+/-14.5, DBH 61.6+/-11.3), but decreased quickly from postnatal week 2 (NPY 6.1+/-3.5, DBH 3.6+/-2.8) onwards. A few NPY- and DBH-immunoreactive ganglion cells were found in the periphery or in the center of the rat carotid body during postnatal development. TH immunoreactivity was observed in almost all chief cells and in a few ganglion cells in all developmental stages. NPY- and DBH-immunoreactive nerve fibers were very scarce in the carotid body from birth to postnatal week 1, began to increase gradually after postnatal week 2, and reached the adult level by postnatal week 5. The present study suggests that the expression of NPY and noradrenaline in chief cells and in the nerve fibers of the rat carotid body may be regulated during postnatal development.