Comparative Study of Catecholaminergic and Nitroxidergic Neurons in the Vasomotor Nuclei of the Caudal Part of the Brainstem in Rats

Abstract

Immunohistochemical studies in 12 Wistar rats detected tyrosine hydroxylase (TH) and the neuronal form of nitric oxide synthase (nNOS) to address the distribution of catecholaminergic and nitroxidergic neurons, respectively, in the vasomotor nuclei of the medulla oblongata and pons. The highest frequency of TH expression was seen in neurons located in these nuclei and some reticular nuclei (the gigantocellular, paragigantocellular, and caudal nuclei of the pons), though the proportions of immunoreactive neurons in these structures were no greater than 8–14%. In other nuclei (the reticular parvocellular and oral nucleus of the pons, the spinal nucleus of the trigeminal nerve), this proportion ranged from 1 to 3%. Neurons of this type were consistently not detected in a large group of nuclei with confirmed vasomotor functions. Structures with many catecholaminergic neurons generally contained fewer nNOS-positive cells than nuclei with limited numbers of TH-positive neurons.