Thin-fiber mechanoreceptors reflexly increase renal sympathetic nerve activity during static contraction.
The renal vasoconstriction induced by the sympathetic outflow during exercise serves to direct blood flow from the kidney toward the exercising muscles. The renal circulation seems to be particularly important in this regard, because it receives a substantial part of the cardiac output, which in resting humans has been estimated to be 20%. The role of group III mechanoreceptors in causing the reflex renal sympathetic response to static contraction remains an open question. To shed some light on this question, we recorded the renal sympathetic nerve responses to static contraction before and after injection of gadolinium into the arterial supply of the statically contracting triceps surae muscles of decerebrate unanesthetized and chloralose-anesthetized cats. Gadolinium has been shown to be a selective blocker of mechanogated channels in thin-fiber muscle afferents, which comprise the afferent arm of the exercise pressor reflex arc. In decerebrate (n = 15) and chloralose-anesthetized (n = 12) cats, we found that gadolinium (10 mM; 1 ml) significantly attenuated the renal sympathetic nerve and pressor responses to static contraction (60 s) after a latent period of 60 min; both responses recovered after a latent period of 120 min. We conclude that thin-fiber mechanoreceptors supplying contracting muscle are involved in some of the renal vasoconstriction evoked by the exercise pressor reflex.
Kim
Jong Kyung
JK
Division of Cardiovascular Medicine, TB-172, University of California, Davis, Davis, CA 95616, USA.
Hayes
Shawn G
SG
Kindig
Angela E
AE
Kaufman
Marc P
MP
D018686:Anesthetics, Intravenous; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D002698:Chloralose; D003655:Decerebrate State; D005682:Gadolinium / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D007668:Kidney / Q000098:blood supply* / Q000294:innervation; D008465:Mechanoreceptors / Q000187:drug effects / Q000502:physiology*; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000294:innervation; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D012026:Reflex, Stretch / Q000187:drug effects*; D012039:Regional Blood Flow / Q000187:drug effects; D012079:Renal Circulation / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects
D018686:Anesthetics, Intravenous; D020030:Nitric Oxide Donors; D009599:Nitroprusside; D002698:Chloralose; D005682:Gadolinium; C038958:gadolinium chloride