Bezold–Jarisch reflex in sino-aortic denervated malnourished rats

Abstract

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 35 days after weaning. These rats underwent sham or SAD and catheterization of femoral artery and vein for BP measurements and drug injection. Phenylbiguanide (PBG 5 μg/kg, i.v.) for activation BJR, produced bradycardia (-317±22 bpm for CN vs. -372±16 bpm for MN) and hypotension (-57±4 mm Hg for CN vs. -54±6 mm Hg for MN. After SAD, MN rats had reduced hypotensive (-37±7 mm Hg for MN vs. -82±6 mm Hg for CN) and bradycardic (-124±17 for MN vs. -414±20 bpm 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 (5 μg/kg) separated by 10 min each other. Both bradycardic (-216±21 bpm before and -4±3 bpm after for CN -226±43 bpm before and -9±20 bpm after for MN) and hypotensive (-42±4 mm Hg before and -6±1 mm Hg after for CN -33±9 mm Hg before and -5±2 mm Hg 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.

Increased α1-adrenoreceptor activity is required to sustain blood pressure in female rats under food restriction

“…Animal studies have shown that absence of a balanced diet (i.e. low protein diets) can affect the sensitivity of these reflexes [5,34]. In our study, we showed that the Bezold-Jarisch reflex is compromised in rats under severe food restriction.…”

“…Remarkably, other dietary challenges can also disrupt the cardiovascular regulatory mechanisms. In this regard, several studies have shown that post-weaning protein malnutrition, in rats, leads to changes in key systems involved in the regulation of systemic blood pressure [5]. Protein malnutrition causes an increased sensibility of the baroreceptor reflex, the chemoreflex [34] and the Bezold-Jarisch [40], a reflex from the heart and lungs that, when activated, leads the inhibition of sympathetic activity [4].…”

Malnutrition affects the pressor response to microinjection of L-glutamate into the RVLM of awake rats

“…This is indicated by the highly linear blood pressure increase in response to L-glutamate microinjection into the RVLM. However, in previous studies our group showed that an autonomic imbalance does occur in post-weaning protein-deprived rats (Martins et al, 2011;Bezerra et al, 2011a;Bezerra et al, 2011b). This lack of modulation of sympathetic activity by the RVLM may explain, in part, the autonomic imbalance observed in previous studies of our group.…”

“…This lack of modulation of sympathetic activity by the RVLM may explain, in part, the autonomic imbalance observed in previous studies of our group. This autonomic imbalance in turn may contribute to the changes observed in the cardiovascular responses to activation of the barorefl ex (Loss et al, 2007), chemorefl ex (Penitente et al, 2007) and von Bezold-Jarisch refl ex (Bezerra et al, 2011a(Bezerra et al, , 2011b. It is well established in the literature that autonomic imbalance and cardiovascular neural refl ex impairment lead to hypertension and cardiovascular diseases.…”

“…Previous studies from our lab have shown that afterweaning malnutrition affects neural mechanisms involved in cardiovascular homeostasis (Bezerra et al, 2011a;Bezerra et al, 2011b;Loss et al, 2007;Martins et al, 2011;Oliveira et al, 2004;Penitente et al, 2007;Tropia et al, 2001). While the exact mechanism remains to be understood, there is evidence indicating that malnutrition can aff ect the release of neurotransmitters and receptor affi nity in several areas of the central nervous system (El et al, 1999;Gotoh et al, 1996;Seidler et al, 1990) The rostral ventrolateral medulla (RVLM) is a bulbar site among the neural pathways of cardiovascular refl exes (e.g., barorefl ex); it contains reticulo-spinal neurons that innervate the pre-ganglionic sympathetic neurons (Ross et al, 1984).…”