Renal vascular response to ganglionic stimulants in the dog.

Abstract

Renal vascular responses to ganglionic stimulants and to renal nerve stimulation were studied in the dog anesthetized with pentobarbital sodium. 1) Ganglionic stimulants, nicotine, DMPP and acetylcholine in the presence of atropine, when given into the renal artery elicited a biphasic elevation in renal perfusion pressure. The first rise in perfusion pressure was completely blocked by phenoxybenzamine and by C6, but not by adrenalectomy. The second rise and a concomitant elevation in the systemic blood pressure were abolished by these two agents as well as by adrenalectomy. 2) Reserpinization of the dog resulted in a marked reduction in the biphasic response thus developed, especially in the first response. Tyramine no longer had a renal vasoconstrictor action, but responses to catecholamines were potentiated. 3) On the seventh to fourteenth day after renal nerve section both tyramine and DMPP lost their immediate vasoconstrictor action. 4) Electrical stimulation of the renal nerve or the splanchnic nerve produced a monophasic or a biphasic elevation in renal perfusion pressure. Such elevations were fully blocked by phenoxybenzamine or C6 as was the case with ganglionic stimulants. However, the blocking site of C6 for splanchnic nerve stimulation was found to be in the extrarenal synapse when a cross-circulation preparation was employed. 5) Perfusion of the kidney with the anoxic blood resulted in a marked reduction in responses to ganglionic stimulants, but no or slight reduction in responses to nerve stimuli. The present data indicate that the biphasic response to ganglionic stimulants is mediated through catecholamines, released from the kidney accounts for the development of the initial response and released from the adrenal gland is attributable to the second response. The catecholamine releasing mechanism of ganglionic stimulants differs from that of tyramine. It is postulated that certain elements, with ganglionic function, even in the absence of anatomical evidence exists in the dog's renal vessels and that the elements have no synaptic function.