Reflex control of cardiac sympathetic nerve activity in anesthetized rats.
Reflex control of sympathetic outflow to the heart was evaluated by recording the efferent discharges of the interior cardiac sympathetic nerves in anesthetized rats. The reflex responses of inferior cardiac sympathetic nerve activity (ICNA) to arterial baroreceptor loading by phenylephrine and to arterial/atrial baroreceptor unloading by hemorrhagic hypotension were compared with those of renal sympathetic nerve activity (RNA) and adrenal sympathetic nerve activity (ANA). The reflex decrease in ICNA to the phenylephrine-induced graded increase in arterial blood pressure was smaller than that of RNA or ANA. Thus ICNA is less sensitive to arterial baroreceptor stimulation. Hemorrhage produced a volume-dependent decrease in ICNA. The response was significantly smaller than that in RNA and was directionally opposite to that in ANA. Cervical vagotomy but not sinoaortic denervation abolished the hemorrhage-induced ICNA response, suggesting an important role of vagal pathways. These findings demonstrate that the reflex responses of sympathetic outflow to the heart were quantitively and qualitatively different from those to the kidney and the adrenal gland, indicating the regional control of sympathetic nerve activity in the regulation of cardiovascular functions.
Tochihara
M
M
First Deparment of Pharmacology, Hokkaido University School of Medicine, Sapporro, Japan.
D000311:Adrenal Glands / Q000294:innervation; D000758:Anesthesia; D000818:Animals; D017704:Baroreflex; D001794:Blood Pressure; D006321:Heart / Q000294:innervation*; D006470:Hemorrhage / Q000503:physiopathology; D007668:Kidney / Q000294:innervation; D008297:Male; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000502:physiology*