In this study we assessed the role of Bezold–Jarisch reflex (BJR) in the regulation of blood pressure (BP) of malnourished (MN) and control rats (CN) with sino-aortic denervation (SAD). Fischer rats were fed diets containing either 6% (MN) or 15% (CN) protein for 35days after weaning. These rats underwent sham or SAD and catheterization of femoral artery and vein for BP measurements and drug injection. Phenylbiguanide (PBG 5μg/kg, i.v.) for activation BJR, produced bradycardia (−317±22bpm for CN vs. −372±16bpm for MN) and hypotension (−57±4mmHg for CN vs. −54±6mmHg for MN. After SAD, MN rats had reduced hypotensive (−37±7mmHg for MN vs. −82±6mmHg for CN) and bradycardic (−124±17 for MN vs. −414±20bpm CN) responses to BJR activation. To evaluate the contribution of the parasympathetic component due to BJR for the fall in BP, methyl atropine bromide, was given between two injections of PBG (5μg/kg) separated by 10min each other. Both bradycardic (−216±21bpm before and −4±3bpm after for CN −226±43bpm before and −9±20bpm after for MN) and hypotensive (−42±4mmHg before and −6±1mmHg after for CN −33±9mmHg before and −5±2mmHg after for MN) responses were abolished in CN and MN groups. These data indicate that dietary protein malnutrition changes the relation between baroreflex and BJR required for maintenance of the BP during malnourishment.
