Effect of Stimulation of the Medulla Oblongata on Renin Secretion in Dogs

Electrodes were implanted in dogs in the dorsal portion of the medulla oblongata near the obex. A week or more later, the electrodes were stimulated while changes in plasma renin activity, plasma epinephrine and norepinephrine, and blood pressure were monitored. Stimulation of 20 points in 16 dogs produced clear-cut increases in plasma renin activity. In almost all instances, these increases were associated with marked increases in blood pressure. There was also a small increase in circulating epinephrine without a significant change in plasma norepinephrine. Stimulation of the medulla 4 h after renal denervation was not associated with any increase in plasma renin activity even though the pressor response was comparable to that before denervation. The response was also absent in dogs stimulated two week after renal denervation. The data show that renin secretion can be increased in association with marked increases in blood pressure. They also show that the increase produced by stimulation of the medulla oblongata is mediated via the renal nerves.