Evaluation of the cardiovascular regulatory mechanisms in the medulla oblongata of the rat: low-intensity electrical activation.

Focal low-intensity (10-20 muA) electrical stimulation in pentobarbital anesthetized rats evoked both hyper- and hypotension from either nucleus reticularis parvocellularis or nucleus reticularis gigantocellularis, the respective representative for classical 'pressor' nd 'depressor' areas in the medulla oblongata. The crucial determinants for the degree of such arterial pressure fluctuations appeared to be the pulse frequency and/or intensity of the activating train pulses. It is suggested that neurons responsible for promoting hyper- and hypotension may exist in intermingled populations within each of these two reticular nuclei, and may possess differential sensitivities to the trainpulse frequency/current intensity used in electrical stimulation.