RESUMO
The study was conducted in normotensive and spontaneously hypertensive rats anesthetized with urethane (1600 mg/kg of animal weight, intraperitoneally). It has been shown that in normotensive rats, injections of a specific inhibitor of Na+, K(+)-ATPase ouabain (10(-8)-10(-5) mol/l) in the populations of the neurons within nucleus of the solitary tract (NTS), paramedian reticular nucleus (PMn) and lateral reticular nucleus (LRN) were accompanied by the development of the hypertensive responses in a dose-dependent fashion. These data suggest that Na+, K(+)-ATPase of the neuron somatic membranes in the medullary cardiovascular nuclei is involved in neural control of the cardiovascular function, and its inhibition by microinjections of ouabain promotes the development of hypertension. In contrast to normotensive rats, ouabain injected in the medullary nuclei of spontaneously hypertensive animals induced either enhanced hypertensive or hypotensive responses. Biochemical analysis revealed that the activity of Na+, K(+)-ATPase in the microsomal fraction of the medulla oblongata of spontaneously hypertensive rats significantly exceeded its activity in the medulla oblongata of normotensive animals. Possible mechanisms of ouabain effects in spontaneously hypertensive rats have being discussed. Activation of Na+, K(+)-ATPase activity of the cardiovascular neurons with asparkam injections in the medullary nuclei resulted in hypotensive responses in both normotensive and spontaneously hypertensive rats.
