Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

<jats:p> Administration of nitric oxide (NO) donors in vivo is accompanied by a baroreflex-mediated increase in heart rate (HR). In vitro, however, NO donors can increase HR directly by stimulating a pathway that involves NO, cGMP, and the hyperpolarization-activated current ( I <jats:sub>f</jats:sub>). The aim of this study was to assess the functional significance of this pathway in vivo by testing whether NO donors can increase HR in the anesthetized rabbit independent of the autonomic nervous system. New Zealand White rabbits were vagotomized, cardiac sympathectomized, and treated with propranolol (0.3 mg/kg iv). The NO donor molsidomine (0.2 mg/kg iv) caused a progressive increase (Δ) in HR (ΔHR, 14 ± 3 beats/min; P &lt; 0.01). This effect was significantly reduced by the I <jats:sub>f</jats:sub> blocker ZD-7288 (0.2 mg/kg iv; ΔHR, 2 ± 3 beats/min; P = not significant). Similar results were seen with sodium nitroprusside. The positive chronotropic effect of sodium nitroprusside (50 μM) was confirmed in the isolated working rabbit heart preparation (ΔHR, 17 ± 3 beats/min; P &lt; 0.01). In conclusion, NO donors exert a small, but significant, positive chronotropic effect in vivo that is independent of the autonomic nervous system. These results are also consistent with data in sinoatrial node cells that show that NO donors increase HR by stimulating I <jats:sub>f</jats:sub>. </jats:p>

Original publication

DOI

10.1152/jappl.1999.87.1.97

Type

Journal article

Journal

Journal of Applied Physiology

Publisher

American Physiological Society

Publication Date

01/07/1999

Volume

87

Pages

97 - 103