title: Vagal C-fiber blockade abolishes sympathetic inhibition by atrial natriuretic factor.
abstract: Administration of atrial natriuretic factor (ANF) to anesthetized rats decreases renal nerve activity (RNA), an effect prevented by vagotomy but not by atropine. We sought to determine whether afferent vagal C-fibers mediate the inhibition of sympathetic outflow. ANF (2.5 micrograms/kg iv) decreased mean arterial pressure (MAP) by 25 +/- 2 mmHg, RNA by 11 +/- 5%, and least splanchnic nerve activity (LSNA) by 10 +/- 4% in anesthetized rats with arterial baroreceptors intact, and by 40 +/- 3 mmHg, 28 +/- 7%, and 23 +/- 4%, respectively, in sinoaortic-denervated rats. Inhibition of RNA and LSNA by ANF was reduced slightly by cooling the vagi to 6 or 7 degrees C, a temperature at which conduction in A-fibers was blocked and that in C-fibers attenuated; inhibition was abolished when C-fibers were blocked by cooling to 0 degrees C. We conclude that the inhibition of RNA and LSNA by ANF was mediated by afferent vagal C-fibers. We also obtained evidence that the aortic nerves contribute to ANF-induced inhibition of RNA. Our results support the notion that ANF evokes a generalized decrease in sympathetic tone that contributes to the hypotension, cardiac inhibition, and natriuresis accompanying systemic administration of the peptide.
authors.affiliation: Department of Medicine, University of California, San Francisco 94143-0130.
authors.forename: H D
authors.initials: HD
authors.lastname: Schultz
authors.forename: D G
authors.initials: DG
authors.lastname: Gardner
authors.forename: C F
authors.initials: CF
authors.lastname: Deschepper
authors.forename: H M
authors.initials: HM
authors.lastname: Coleridge
authors.forename: J C
authors.initials: JC
authors.lastname: Coleridge
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure; D003714:Denervation; D005260:Female; D006339:Heart Rate; D007668:Kidney / Q000294:innervation; D009407:Nerve Block; D009412:Nerve Fibers / Q000187:drug effects*; D009599:Nitroprusside / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013153:Splanchnic Nerves / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects*; D014628:Vagotomy; D014630:Vagus Nerve / Q000187:drug effects*
chemical_list: D009599:Nitroprusside; D001285:Atropine; D009320:Atrial Natriuretic Factor