Abstract
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.
Highlights
Lying in the dorsomedial medulla oblongata and consisting of the nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus (DMV), and area postrema (AP), the dorsal vagal complex (DVC) has a known involvement in autonomic functions such as cardiovascular, respiratory and visceral regulation
Dendrites and fine varicose fibers of the locus coeruleus (LC) were distinctly immunostained by the present antibody anti-NA (Figure 1B), though we observed no immunostaining after incubation in the antibody preabsorbed by the antigen NA-G-acetyl-L-Lysine N-methylamine (ALM) (Figure 1C)
DA immunoreactivity in the DVC was very weak in non-treated and slightly less weak in monoamine oxidase inhibitor (MAOI)-treated animals (Figure 1H), whereas we found intense NA immunoreactivity in this same structure (Figures 1K, and cf.3E)
Summary
Lying in the dorsomedial medulla oblongata and consisting of the nucleus of the solitary tract (NTS), dorsal motor nucleus of the vagus (DMV), and area postrema (AP), the dorsal vagal complex (DVC) has a known involvement in autonomic functions such as cardiovascular, respiratory and visceral regulation. The DVC and ventrolateral medulla (VLM) play a major role in the central control of the cardiorespiratory and other parts of the autonomic nervous system. The NTS receives a variety of neurovegetative inputs from peripheral receptors and is crucially involved in integrating the information arising from the bronchopulmonary and arterial baro- or chemoreceptors. Arising from airways and chemosensory fibers in the chemoreceptors of the peripheral artery, these fibers project to the caudomedial NTS in the commissural nucleus (COM) close to the central canal [1,2]. Many neurons and Received December 09, 2014; Accepted November 26, 2015; Published December 08, 2015
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