生理的濃度の血漿中ノルエピネフリンは心臓交感神経による動的心拍数調節に影響を与えない

抄録

Purpose: Although the sympathetic nervous system regulates the heart via both humoral and neural factors, interaction between the two factors remains unknown. The purpose of the present study was to elucidate the effects of plasma NE on dynamic heart rate (HR) regulation by the cardiac sympathetic nerve. Methods: In 7 anethetized rabbits with vagotomy, we stimulated the right cardiac sympathetic nerve using a binary white noise (0-1 Hz, 2-s switching interval) while measuring the HR response. Effects of continuous intravenous infusion of NE at 1 and 10 μg/kg/h on the transfer function from sympathetic stimulation to HR were examined. Results: NE infusions at 1 and 10 μg/kg/h increased plasma NE concentration from 547±128 to 965±118 and 7120±1080 pg/ml (means±SE), respectively. The transfer function from sympathetic stimulation to HR approximated a second-order low-pass filter with lag time. Dynamic gain did not differ among conditions of control and NE infusions (5.4±1.4, 5.2±0.9, 5.3±1.1). Other parameters of the transfer functions including natural frequency, damping ratio, and lag time did not differ among the three conditions. Conclusion: Plasma NE concentration up to approximately 10 times a resting level hardly affected dynamic HR response to sympathetic stimulation. The neural regulation appears predominant over the humoral regulation in the sympathetic control of HR. [Jpn J Physiol 55 Suppl:S88 (2005)]