AJP - Heart and Circulatory Physiology, Vol 237, Issue 3 326-H331, Copyright © 1979 by American Physiological Society
Presynaptic inhibition of canine renal adrenergic nerves by acetylcholine in vivo
N. W. Robie
Experiments were performed in anesthetized dogs to determine whether
previously reported in vitro inhibition of sympathetic neurotransmitter
release by acetylcholine could be demonstrated in the renal vasculature of
the intact animal. Vasoconstrictor responses to renal sympathetic nerve
stimulation at varying frequencies were compared to intra-arterial
injections of norepinephrine before and during intra-arterial infusions of
acetylcholine, 2.5--80 micrograms/min. The vasoconstrictor responses to
nerve stimulation were inhibited to a greater extent than were responses to
norepinephrine during infusions of acetylcholine. The inhibitory effects of
acetylcholine on nerve stimulation were dose and frequency dependent. The
inhibition was blocked by atropine but not altered by physostigmine.
Changes in renal blood flow per se did not contribute to the inhibitory
effect of acetylcholine, since another vasodilator agent, sodium acetate,
did not affect the nerve stimulation-norepinephrine vasocontriction
relationship. Thus, acetylcholine produced inhibition of in vivo renal
sympathetic vasoconstrictor responses, and the receptor involved appears to
be muscarinic.
