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The effects of direct renal nerve stimulation (RNS) on renal tilood flow (RBF) have been studied by a number of investigators (1-3). However, most studies involved indirect measurements of RBF by clearance techniques which (a) limit measurements to steady state conditions, and (b) require arterial and renal venous blood samples so that repeated measurements in the same animal could result in modest decreases of circulating blood volume. Although excellent direct methods for measuring RBF are available (4), such procedures do not permit facile and accurate examination of RBF changes during commencement, maintenance, and cessation of RNS.In the present study, RBF changes during direct RNS were measured with an electromagnetic flowmeter. This technique permits examination of transient and sustained flow changes during RNS over a wide range of frequencies in the presence and absence of autonomic blocking drugs. The results show that extent of renal vasoconstriction is directly proportional to frequency of RNS a t frequencies between 1 and 10 cycles per second (cps), maximal a t 10 cps, and inversely proportional to frequency at frequencies greater than 10 cps. They also show that RBF returns to control flow levels during continued RNS at frequencies above 10 cps. Renal vasoconstrictor responses during RNS appear to be due to activation of alpha-adrenergic receptors, while beta-adrenergic and cholenergic receptors do not seem to be involved. NO evidence for extrinsic renal vasodilator innervation was obtained. Methods.Experiments were performed in 20 mongrel dogs (15-20 kg), of either sex, anesthetized with sodium pentobarbital (30 mg/kg, iv 30-60 min. following subcutaneous injection of morphine sulfate (3 mg/kg). Each animal breathed spontaneously throughout the experiment. Central arterial and venous pressures were continuously monitored through catheters inserted into the right femoral artery and vein and advanced centrally until their tips were close to the heart. The catheters were attached to Statham P23AC pressure transducers which were connected to a Grass Model 5 polygraph.The left renal artery was exposed through a retroperitoneal incision. RBF was measured with a noncannulating electromagnetic flow sensor (Statham-Medicon) of the gated sine wave type. Zero flow base line was determined at the beginning of each experiment and checked at the termination of the experiment by occluding the artery distal to the flow sensor.The renal nerves were isolated and tied with two silk ligatures. The nerve bundle was severed between the ligatures, kept warm and moist, and the peripheral end was stimulated with platinum electrodes. Square wave stimuli of 2-msec duration and variable frequencies (1-200 cps) were delivered from a Grass SD 5 stimulator. In each experiment, voltage (15-30 V ) was adjusted until a maximal response occurred at 10 cps. The duration of each stimulus trial (20-30 sec), and elapsed time between trials (1-2 min) was constant in each experiment.Autonomic blocking drugs, dissolved in saline, were inje...

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The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.