Angiotensin II supports sympathetically mediated vasopressor response to footshock-stress

The present study was carried out to assess whether endogenous angiotensin II (Ang II) supports sympathetically mediated cardiovascular response to stress in conscious unrestrained rats, using experimental models in which the renin-angiotensin-system was reduced or blocked. Footshock-stress increased mean arterial pressure (MAP) and heart rate (HR). Inhibition of angiotensin-converting enzyme with captopril or blockade of AT(1)angiotensin receptor with losartan, attenuated vasopressor responses to footshocks, while heart rate response was not altered. Bilateral nephrectomy suppressed vasopressor response as well the elevation of plasma noradrenaline and adrenaline induced by footshocks, and reduced heart rate response. Cardiovascular response to stress in nephrectomised rats was restored by exogenous administration of a subpressor dose of Ang II. Our results demonstrate that in conscious rats cardiovascular response to footshocks is dependent on an active renin-angiotensin system and they indicate that endogenous Ang II supports the sympathetically mediated vasopressor response to footshocks.