Nitric oxide mediation of cardiac receptor reflex responses in the pregnant rat.

Objectives: Our purpose was to determine the contribution of centrally released nitric oxide to baseline sympathetic tone and reflex cardiovascular responses to cardiac stretch in the pregnant rat.Study Design: Baseline blood pressure and renal sympathetic nerve activity and reflex changes in these variables in response to intraatrial saline solution injections were measured in anesthetized pregnant (n = 24) and virgin (n = 27) rats before and after bilateral microinjection of L-nitroarginine methyl ester (0.01 to 1 micromol) into the dorsal medulla. Data were analyzed with use of nonparametric analysis of variance.Results: L-Nitroarginine methyl ester microinjection altered basal blood pressure and sympathetic nerve activity (p < 0.05) in virgin but not pregnant rats. L-Nitroarginine methyl ester significantly and equivalently attenuated the reflex sympathoinhibitory and depressor responses to cardiac stretch for 40 minutes in pregnant and virgin animals.Conclusion: Central nitric oxide does not modulate basal sympathetic tone in the pregnant rat but is released in the medulla in response to cardiac stretch and plays a role in reflex cardiovascular responses similar to that in virgin rats. [ABSTRACT FROM AUTHOR]

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