In 11 cordotomized (C₂) rats with the vagi cut, monopolar electrical stimulation at a current intensity of 73±21 (S.E.) μA (n=6) to the intermediate region of the solitary nucleus elicited an increase (p<0.05) in regional blood flow (iodoantipyrine technique) of 71% and 43% in the frontal cortex and caudate nucleus, respectively. The findings suggest that some of the cardio-pulmonary and Cardio-vascular reflex mechanisms are involved in the regulation of the blood vessels of the brain.