Noradrenaline-immunoreactive Neurons in Cat Dorsal Vagal Complex, Following Administration of Pargyline, Parachlorophenylalanine or Colchicine

Abstract

The localization and chemical nature of neurons immunoreactive to noradrenaline (NA) in the cat dorsal vagal complex (DVC) was examined, using immunohistochemistry for NA, dopamine-\(\beta\)-hydroxylase (DBH), dopamine (DA) and tyrosine hydroxylase, under different conditions.  The localization of NA-immunoreactive (-ir) and DBH-ir neurons in non-treated mice was highly overlapping. They were mostly found in nucleus of solitary tract (NTS) and a small number in dorsal motor nucleus of vagus. The commissural and ventral subnuclei of NTS contained the majority of NA-ir / DBH-ir neurons. A small number of weakly stained NA-ir cell bodies coexisted with numerous intensely stained DBH-ir cell bodies in the area postrema. Injection of a monoamine oxidase inhibitor (MAOI), pargyline, enhanced NA immunoreactivity in cells and axons of DVC and increased their number. Both DA and NA immunoreactivities were drastically reduced in a large number of axons after treatment with MAOI + parachlorophenylalanine, an inhibitor of tryptophan and phenylalanine hydroxylases, however NA immunoreactivity in DVC cell bodies remained detectable. Colchicine + MAOI treatment increased NA immunoreactivity exclusively in cell bodies in the locations mentioned above, where NA and DBH immunoreactivity was weak or undetectable. The physiological consequences were discussed referring to the previous reports.