title: Volume loading inhibits baroreflex vagal bradycardia in rats.
abstract: Volume loading tends to increase blood pressure. Resultant arterial baroreflexes, especially the heart rate component, would counteract renal compensation of volume expansion. In this study, we investigated effect of volume loading on baroreflex vagal bradycardia (BVB) induced by electrical stimulation of the aortic depressor nerves in chloralose/urethane-anesthetized, succinylcholine-immobilized, artificially ventilated rats. As a result, we confirmed that volume loading inhibits BVB. The inhibition was abolished following spinal cord transection at C2. In contrast, volume loading did not affect the bradycardia induced by electrical stimulation of peripheral cut ends of the cervical vagus. These findings suggest that the inhibition of BVB by volume loading is mediated by afferent input which is conveyed in the sympathetic nerves and ascends in the spinal cord, and produced at a central site.
authors.affiliation: Department of Physiology, Mie University School of Medicine, Tsu, Japan.
authors.forename: Shima
authors.initials: S
authors.lastname: Morooka
authors.forename: Naoko
authors.initials: N
authors.lastname: Asano
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Nosaka
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology*; D001919:Bradycardia / Q000503:physiopathology*; D004558:Electric Stimulation; D006321:Heart / Q000294:innervation* / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D008297:Male; D009433:Neural Inhibition / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000502:physiology*; D013119:Spinal Cord Injuries / Q000503:physiopathology; D014630:Vagus Nerve / Q000502:physiology*; D017833:Visceral Afferents / Q000502:physiology*