Navegando por Autor "Silva Junior, Luiz Gonzaga da"
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Item Blunted gaba-mediated inhibition within the dorsomedial hypothalamus potentiates the cardiovascular response to emotional stress in rats fed a high-fat diet.(2014) Abreu, Aline Rezende Ribeiro de; Abreu, Alessandra Rezende Ribeiro de; Santos, Laura Tavares; Souza, Aline Maria Arlindo de; Silva Junior, Luiz Gonzaga da; Chianca Júnior, Deoclécio Alves; Menezes, Rodrigo Cunha Alvim deRats fed a high-fat diet (HFD) present an exaggerated endocrine response to stress conditions, which, like obesity, show a high correlation with cardiovascular diseases. Meanwhile the GABAergic neurotransmission within the dorsomedial hypothalamus (DMH) is involved in the regulation of the physiological responses during emotional stress. Here we evaluated the influence of obesity, induced by a HFD, on the cardiovascular responses induced by air jet stress in rats, and the role of the GABAergic tonus within the DMH in these changes. Our results showed that consumption of a HFD (45% w/w fat) for 9 weeks induced obesity and increases in baseline mean arterial pressure (MAP) and heart rate (HR). Moreover, obesity potentiated stress responsiveness, evidenced by the greater changes in MAP and HR induced by stress in obese rats. The injection of muscimol into the DMH reduced the maximal increases in HR and MAP induced by stress in both groups; however, the reduction in the maximal increases in MAP in the HFD group was less pronounced. Moreover, the injection of muscimol into the DMH of obese rats was less effective in reducing the stress-induced tachycardia, since the HR attained the same levels at the end of the stress paradigm as after the vehicle injection. Injection of bicuculline into DMH induced increases in MAP and HR in both groups. Nevertheless, obesity shortened the tachycardic response to bicuculline injection. These data show that obesity potentiates the cardiovascular response to stress in rats due to an inefficient GABAA-mediated inhibition within the DMH.Item Increased activity of the renin-angiotensin and sympathetic nervous systems is required for regulation of the blood pressure in rats fed a low-protein diet.(2013) Gomide, Joelma Maria Cardoso; Menezes, Rodrigo Cunha Alvim de; Fernandes, Luciano Gonçalves; Silva, Fernanda Cacilda dos Santos; Cardoso, Leonardo Máximo; Miranda, P. H.; Silva Junior, Luiz Gonzaga da; Lima, Mercia de Paula; Pesquero, Jorge Luiz; Heida, Giselle Foureaux; Ferreira, Anderson José; Chianca Júnior, Deoclécio AlvesPrevious studies have shown that postweaning protein restriction induces changes in the sympathetic nervous system in rats, leading to alterations in cardiovascular parameters. In addition, the renin–angiotensin system is also affected in these animals. Here, we hypothesized that adjustments in the interaction between the RAS and SNS underlie the cardiovascular adaptations observed in rats fed a low-protein diet. Thus, we evaluated the alterations in the mean arterial pressure (MAP) and heart rate of Fisher rats fed a protein-deficient diet before and after systemic administration of the angiotensin-converting enzyme inhibitor enalapril and the angiotensin II (Ang II) type 1 (AT1) receptor antagonist losartan alone or in combination with the α1-adrenergic receptor antagonist prazosin. Administration of enalapril or losartan decreased the MAP only of rats under protein restriction. Prazosin injection after the infusion of losartan caused a further decrease in the MAP of malnourished rats. In contrast, only the administrationof prazosin elicited a reductionin theMAPof control animals.Whenthe sequence of administrationof the antagonistswasinverted, infusion of prazosin inanimals fedthe standard or the low-protein diet induced a reduction in the MAP that was further decreased by the subsequent injection of losartan. Importantly, in both protocols the responses ofmalnourished animals to losartan were markedly greater when compared with the control group. Moreover, these animals presented lower levels of circulatingAng II and a reduced responsiveness to Ang II. In contrast, the expression of AT1 receptors in the aorta ofmalnourished animals was increased. Thus, our data suggest that the renin–angiotensin system is an important factor supporting blood pressure in rats fed a low-protein diet and that the sympathetic nervous system activity in these animals is under strong influence of Ang II acting via AT1 receptors.Item Thermoregulatory responses, heart rate, and the susceptibility to anxiety in obese animals subjected to stress.(2023) Santos, Áquila Rodrigues Costa; Abreu, Aline Rezende Ribeiro de; Noronha, Sylvana Izaura Salyba Rendeiro de; Reis, Thayane Oliveira; Santos, Daisy Motta; Chianca Júnior, Deoclécio Alves; Silva Junior, Luiz Gonzaga da; Menezes, Rodrigo Cunha Alvim de; Rodrigues, Cibele VellosoObesity and stress are related to cardiovascular diseases. Rats fed a high-fat diet (HFD) show increased cardiovascular reactivity to emotional stress and altered defensive behavioral responses. Indeed, changes in thermoregulatory responses in an aversive environment are observed in these animals. However, studies aimed at clarifying the physiological mechanisms linking obesity, stress hyperreactivity and behavioral changes are needed. The aim of this study was to evaluate the changes in thermoregulatory responses, heart rate, and the susceptibility to anxiety in obese animals subjected to stress. Nine-week high-fat diet protocol was effective in inducing obesity by increasing weight gain, fat mass, adiposity index, white epididymal, retroperitoneal, inguinal and brown adipose tissue. Animals induced to obesity and subjected to stress (HFDS group) by the intruder animal method showed increases in heart rate (HR), core body temperature and tail temperature. HFDS showed an increase in the first exposure to the closed arm (anxiety-like behavior) in elevated T-Maze (ETM). The groups did not differ with respect to panic behavior assessed in the ETM and locomotor activity in the open field test. Our study shows that HFDS animals presented increased reactivity to stress with higher stress hyperthermia and anxious behavior. Thus, our results present relevant information regarding stress responsiveness and behavioral changes in obese animals.