Keiko Ikemoto, Michael Geffard, Yves Tillet and Kunio Kitahama
We examined the localization and chemical nature of neurons immunoreactive to noradrenaline (NA) in the cat’s dorsal vagal complex (DVC), using immunohistochemistry for NA, dopamine-β-hydroxylase (DBH), dopamine (DA) and tyrosine hydroxylase, under different conditions. In non-treated animals, localization of NA-immunoreactive (-ir) and DBH-ir neurons extensively overlapped. They were found mainly in the caudal portion of the nucleus of the solitary tract (NTS), and a small number in the dorsal motor nucleus of the vagus. Most were restricted to the commissural and ventral sub nuclei of the NTS. In the area postrema, we observed a small number of weakly stained NA-ir cell bodies alongside numerous intensely stained DBH-ir ones. Injection of the monoamine oxidase inhibitor (MAOI), pargyline, enhanced NA immunoreactivity in cells and axons of the DVC and increased their number. Treatment with MAOI plus parachlorophenylalanine, an inhibitor of tryptophan and phenylalanine hydroxylases, dramatically decreased both DA and NA immunoreactivities in a large number of axons, although NA immunoreactivity in cell bodies of the DVC remained visible. Treatment with Colchicine+MAOI intensified NA immunoreactivity exclusively in cell bodies in areas described above and where immunoreactivity to NA and DBH was weak and/or undetectable. The physiological implications were discussed referring to the previous reports.