Malnutrition alters the cardiovascular responses induced by central injection of tityustoxin in Fischer rats.

Scorpion envenoming and malnutrition are considered two important public health problems in Brazil, involving mainly children. Both these conditions are more common among the economically stratified lower income portion of the population, thus suggesting that these factors should be analyzed concomitantly. It is known that cardiorespiratory manifestations, as cardiac arrhythmias, arterial hypertension and hypotension, pulmonary edema and circulatory failure are the main "causa mortis" of scorpion envenomation. Additionally, there are evidences in the literature that deficiencies in dietary intake endanger the CNS and modify the cardiovascular homeostasis. Then, the objective of this work is to evaluate the protein malnourished effect on cardiovascular responses induced by tityustoxin (TsTX, an α-type toxin extracted from the Tityus serrulatus scorpion venom). Fischer rats (n = 20) were injected i.c.v. with TsTX and divided in control and malnorished groups, which were, respectively, submitted to a control and a low-protein diet. Arterial pressure recordings were done until death of the animals. Although both groups presented an increased mean arterial pressure after TsTX injection, this increase was smaller and delayed in malnourished rats, when compared to control rats. In addition, heart rate increased only in rats from the control group. Finally, malnourished rats had an increase in survival time (9:9/13.5 vs. 15.5:10.5/18 min; p = 0.0009). In summary, our results suggest that the protein restriction attenuates the cardiovascular manifestations resulting from TsTX action on CNS.

Protein malnutrition modifies medullary neuronal recruitment in response to intermittent stimulation of the baroreflex.

Protein malnutrition after weaning changes the neurotransmission in neural pathways that organize cardiovascular reflexes in rats. The present study evaluates whether protein malnutrition alters the expression of c-fos protein (immediate-early gene expression) in central areas involved in the control of cardiovascular reflexes after intermittent stimulation of the baroreflex. The main nuclei we focused were paraventricular hypothalamus (PVH); nucleus tract solitarii (NTS); rostral ventromedial medulla (RVMM); rostral (RVLM) and caudal ventrolateral medulla (CVLM). Male Fisher rats at 28 days were submitted to two different isocaloric diets during the subsequent 35 days: control (CT) (15% protein) and malnourished (MN) (6% protein). thirtymin of intermittent (every 3 min) baroreflex stimulation was performed by infusing phenylephrine (Phe-0.25 mM) or, as control, 0.9% NaCl (Sal). Following ninety minutes, animals were anesthetized and perfused. The removed brains were sectioned (35 µm) and used for c-fos immunohistochemistry. Images were analyzed using the software Leica Q Win. Despite not altering the baseline MAP, malnutrition increased baseline HR and expression of c-fos in RVMM. Increases in c-fos expression after intermittent stimulation of baroreflex were evident in the PVH, medial NTS and CVLM in both dietary protocols. Current data further revealed a differential neuronal recruitment to stimulation of baroreflex in the caudal commissural and rostral NTS and RVLM of MN. We conclude that protein malnutrition modifies the cardiovascular control and the pattern of central response to baroreflex stimulation.