CEREBELLAR PRESSOR-RESPONSE IN DOG

A fastigial pressor response was elicited in the anesthetized mongrel dog. Stimulation within the rostral portions of this nucleus results in mean arterial pressure rises up to 150 mmHg above control. A proportional tachycardia is simultaneously evoked which may rapidly attain heart rates of 190 beats/min above control levels. Peak tachycardias immediately subside, and the heart rate often declines below control values during stimulation while arterial pressure remains elevated. When the carotid sinuses were isolated by ligation or a bilateral vagotomy was performed, the fastigial tachycardia was sustained. Thresholds for the response are near 0.05 mA and the stimulus intensity curve is linear to 0.4 mA whereupon the pressure rise and tachycardia begin to approach a plateau value. The response could still be attained when submaximal doses of .alpha.-chloralose anesthesia or high levels of barbiturates (30-40 mg/kg) were given. Both portions of the response result from widespread sympathetic activation; buffering of the response through the baroreceptor reflexes is only demonstrated in the cardiac segment of the response.