Endogenous nitric oxide derived from nos I or II in thoracic spinal cord exerts opposing tonic modulation on sympathetic vasomotor tone via disparate mechanisms in anesthetized rats

Yan Yuen Poon, Ching Yi Tsai, Chung Dar Cheng, Alice Y.W. Chang, Samuel H.H. Chan

研究成果: Article同行評審

9 引文 斯高帕斯(Scopus)

摘要

The sympathetic preganglionic neurons (SPN) in the thoracic spinal cord regulate vasomotor tone via norepinephrine released from sympathetic terminals and adrenal medulla. We assessed the hypothesis that nitric oxide synthase I (NOS I)-and NOS II-derived nitric oxide (NO) in the thoracic spinal cord differentially modulate sympathetic outflow and that the adrenal medulla may be involved in those modulatory actions. In Sprague-Dawley rats, NOS I immunoreactivity was distributed primarily in the perikaryon, proximal dendrites, or axons of SPN, and small clusters of NOS II immunoreactivity impinged mainly on the circumference of SPN. Intrathecal administration of 7-nitroindazole (7-NI), a specific NOS I antagonist, into the thoracic spinal cord significantly reduced arterial pressure, heart rate, and basal or baroreflex-mediated sympathetic vasomotor tone. On the other hand, intrathecal application of S-methylisothiourea (SMT), a specific NOS II antagonist, elevated arterial pressure with a transient reduction of heart rate, induced a surge of plasma norepinephrine, and reduced baroreflex-mediated but not basal sympathetic vasomotor tone. Bilateral adrenalectomy significantly exacerbated the cardiovascular responses to 7-NI but antagonized those to SMT. We conclude that both NOS I and NOS II are present in the thoracic spinal cord and are tonically active under physiological conditions. Furthermore, the endogenous NO generated by NOS I-containing SPN exerts a tonic excitatory action on vasomotor tone mediated by norepinephrine released from the adrenal medulla and sympathetic nerve terminals. On the other hand, NO derived from NOS II exerts a tonic inhibitory action on sympathetic outflow from the SPN that targets primarily the blood vessels.

原文English
頁(從 - 到)H555-H562
期刊American Journal of Physiology - Heart and Circulatory Physiology
311
發行號3
DOIs
出版狀態Published - 2016 九月

All Science Journal Classification (ASJC) codes

  • 生理學
  • 心臟病學與心血管醫學
  • 生理學(醫學)

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