Abstract
Summary
Changes in canine renal blood flow (RBF) during direct renal nerve stimulation (RNS) were measured with an electromagnetic flowmeter in the presence and absence of autonomic blocking drugs. The degree of renal vasoconstriction increases as frequency of RNS is increased from 2 to 10 cps. Above 20 cps the degree of vasoconstriction decreases. During continued RNS at high frequencies (>10 cps) RBF returns to control flow level. Renal vasoconstriction during RNS is blocked by alpha-adrenergic blockade, unaltered by beta-adrenergic or ganglionic blockade, and absent in reserpinized animals. These findings suggest that decrease in RBF during RNS is due to activation of alpha-adrenergic receptors by norepinephrine and that the pathway between constrictor fibers and renal vascular smooth muscle probably does not involve ganglionic synapses. No evidence for participation of cholinergic, or beta-adrenergic receptors during RBF responses to RNS, or for the occurrence of extrinsic renal vasodilator nerves was obtained.
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