The interaction between renin-angiotensin system and sympathetic nervous system in the peripheral vasculature of normal Sprague-Dawley rats
To evaluate possible interactions between the renin-angiotensin system (RAS) and the sympathetic nervous system (SNS) in the systemic circulation upon the intravenous administration of angiotensin II and a set of adrenergic agonists in normal Sprague-Dawley (SD) rats. Rats were treated with carvedilol, a non-selective b- and selective a1-adrenoceptor blocker, in a dose of (5 mg/kg) orally for 7 days, and on day 8, the animals were pentobarbitone-anaesthetized and prepared for systemic hemodynamic study. Dose-response relationships in terms of elevation in the magnitude of the mean arterial blood pressure in response to intravenous injection of noradrenaline (NA), phenylephrine (PE), methoxamine (ME), and angiotensin II (Ang II) were determined. Data, mean ± S.E.M., were subjected to ANOVA with significance at P < 0.05. Carvedilol blunted the peripheral vascular response to NA, PE, ME, and Ang II (all P < 0.05). It is concluded that peripheral vasoconstriction induced by Ang II is contributed to by adrenergic action. Furthermore, there is a cross-talk relationship between RAS and SNS in determining the responsiveness of the peripheral vasculature to adrenergic agonists and angiotensin II in normal rats.
Key words: Carvedilol, methoxamine, angiotensin II, Sprague-Dawley rats