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.