Norepinephrinergic and nitroxidergic neurons of vasomotor nuclei in hypertensive rats

The distributions of norepinephrinergic and nitroxidergic neurons in solitary tract nucleus, locus coeruleus, and in the small-celled and gigantocellular reticular nuclei were examined in sham-operated and experimental Wistar rats with induced renovascular hypertension. In control rats, the greatest population of norepinephrinergic cells was revealed in the projections of locus coeruleus and reticular gigantocellular nuclei, while the larger number of nitroxidergic neurons were observed in the solitary tract and the small-celled nuclei. During renovascular hypertension, the earliest and the most pronounced changes in luminescence intensity and the number of nitroxidergic neurons were observed in the solitary tract nucleus, while the changes in locus coeruleus were minimal. The significant changes in similar parameters of norepinephrinergic neurons were documented only in reticular gigantocellular nucleus and locus coeruleus, but they were delayed and less pronounced in comparison with the changes of nitroxidergic neurons.

Changes in neurons of medulla oblongata nuclei under conditions of chronic NO-synthase inhibition

Nucleus tractus solitarius and giant-cell and lateral reticular nuclei were studied using the reaction to NADPH-diaphorase in 7-, 10-, 14-, 30-, 45-, 60-day-and 3- and 6-month-old rats receiving L-NAME (50 μg/kg, 2 times a day) on days 1-6 of life. In 7-14-day-old rats, the compound reduced NO-synthase activity in the majority of NO-neurons and the total number and to a lesser degree the relative number of these neurons, while cell cross-section areas remained practically unchanged. The differences in the corresponding quantitative parameters between the control (D-NAME administration) and experimental groups decreased with time after the last L-NAME injection and became undetectable starting from the age of 30-45 days. In the nucleus tractus solitarius, the changes in metric parameters after exposure to NO-synthase inhibitor were more pronounced than in the reticular formation nuclei.

Nitroxidergic neurons in nuclei of the medulla oblongata in hypertensive and normotensive rats

Distribution of nitroxidergic neurons and neuronal NO-synthase activity in certain medulla oblongata nuclei were studied in normotensive and hypertensive rats with different types of arterial hypertension. In rats with renovascular hypertension, neuronal NO-synthase activity markedly decreased in most nuclei 2 weeks after surgery, while the number of NO-positive cells did not change significantly; after 4 weeks, the percentage of NO-positive neuron markedly decreased and neuronal NO-synthase activity also slightly decreased. No further decrease in neuronal NO-synthase activity was observed 8 week after intervention, but the percentage of NO-neurons decreased compared to that in normotensive rats. In spontaneously hypertensive rats, changes in most nuclei were directed similarly to those observed in 8-week renovascular hypertension, but motor nuclei demonstrated less differentiated reaction to hypertension. In all cases, changes in the parameters observed in sensory nucleus (n. solitarius) appeared earlier and were more pronounced than in nuclei of the reticular formation related to bulbar vasomotor center.

NO-positive neurons in some nuclei of human bulbar vasomotor center in arterial hypertension

The distribution of nitroxidergic neurons and activities of neuronal NO synthase in them in some nuclei of the bulbar vasomotor center were studied in patients with early forms of arterial hypertension. Activity of neuronal NO synthase is reduced significantly in the majority of nuclei in patients with early forms of arterial hypertension, while the content of NO-positive cells was only slightly changed. More pronounced changes in this parameter were detected in the solitary tract nuclei in comparison with the reticular formation nuclei, which had efferent relationships with the intermediate lateral spinal nucleus.