Serotoninergic Modulation of Basal Cardiovascular Responses and Responses Induced by Isotonic Extracellular Volume Expansion in Rats / Modulação Serotoninérgica de Respostas Cardiovasculares Basais e Induzidas pela Expansão Isotônica do Volume Extracelular em Ratos

Abstract Background: Isotonic blood volume expansion (BVE) induced alterations of sympathetic and parasympathetic activity in the heart and blood vessels, which can be modulated by serotonergic pathways. Objective: To evaluate the effect of saline or serotonergic agonist (DOI) administration in the hypothalamic paraventricular nucleus (PVN) on cardiovascular responses after BVE. Methods: We recorded pulsatile blood pressure through the femoral artery to obtain the mean arterial pressure (MAP), systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR) and the sympathetic-vagal ratio (LF/HF) of Wistar rats before and after they received bilateral microinjections of saline or DOI into the PVN, followed by BVE. Results: No significant differences were observed in the values of the studied variables in the different treatments from the control group. However, when animals are treated with DOI followed by BVE there is a significant increase in relation to the BE control group in all the studied variables: MBP (114.42±7.85 vs 101.34±9.17); SBP (147.23±14.31 vs 129.39±10.70); DBP (98.01 ±4.91 vs 87.31±8.61); HR (421.02±43.32 vs 356.35±41.99); and LF/HF ratio (2.32±0.80 vs 0.27±0.32). Discussion: The present study showed that the induction of isotonic BVE did not promote alterations in MAP, HR and LF/HF ratio. On the other hand, the injection of DOI into PVN of the hypothalamus followed by isotonic BVE resulted in a significant increase of all variables. Conclusion: These results suggest that serotonin induced a neuromodulation in the PVN level, which promotes an inhibition of the baroreflex response to BVE. Therefore, the present study suggests the involvement of the serotonergic system in the modulation of vagal reflex response at PVN in the normotensive rats.

Resumo Fundamento: Expansão de volume extracelular (EVEC) promove alterações da atividade simpática e parassimpática no coração e vasos sanguíneos, os quais podem ser moduladas por vias serotoninérgicas. Objetivo: Avaliar o efeito da administração de salina ou agonista serotoninérgico (DOI) nos núcleos paraventriculares hipotalâmico (NPV) sobre respostas cardiovasculares após EVEC. Métodos: Foram obtidos registros da pressão arterial pulsátil, por meio da artéria femoral, para obtenção dos valores da pressão arterial média (PAM), sistólica (PAS), diastólica (PAD), frequência cardíaca (FC) e razão simpático-vagal (LF/HF) de ratos Wistar antes e após receberem microinjeções bilaterais no NPV de salina ou DOI seguida de EVEC. Resultados: Não foram observadas diferenças significativas dos valores das variáveis estudadas nos diferentes tratamentos do grupo controle. Entretanto, quando os animais são tratados com DOI seguida de EVEC ocorre aumento significativo em relação ao grupo controle com EVEC em todas as variáveis estudadas: PAM (114,42±7,85 vs 101,34±9,17), PAS (147,23±14,31 vs 129,39±10,70), PAD (98,01 ±4,91 vs 87,31±8,61), FC (421,02±43,32 vs 356,35±41,99) e LF/HF (2,32±0,80 vs 0,27±0,32). Discussão: O presente estudo mostrou que a indução de EVEC isotônica não promoveu alterações na PAM, PAD, PAS, FC e LF/HF. Por outro lado, os animais que receberam microinjeção de DOI no NPV seguida de EVEC apresentaram aumento significativo de todas as variáveis. Conclusão: Esses resultados sugerem que a serotonina exerce uma neuromodulação em nivel do NPV, e essa promove uma inibição da resposta barorreflexa frente à EVEC. Assim, o presente trabalho sugere o envolvimento serotoninérgico na neuromodulação no nivel do NPV na resposta reflexa vagal em ratos normotensos.

Serotoninergic Modulation of Basal Cardiovascular Responses and Responses Induced by Isotonic Extracellular Volume Expansion in Rats.

BACKGROUND:: Isotonic blood volume expansion (BVE) induced alterations of sympathetic and parasympathetic activity in the heart and blood vessels, which can be modulated by serotonergic pathways. OBJECTIVE:: To evaluate the effect of saline or serotonergic agonist (DOI) administration in the hypothalamic paraventricular nucleus (PVN) on cardiovascular responses after BVE. METHODS:: We recorded pulsatile blood pressure through the femoral artery to obtain the mean arterial pressure (MAP), systolic (SBP) and diastolic blood pressure (DBP), heart rate (HR) and the sympathetic-vagal ratio (LF/HF) of Wistar rats before and after they received bilateral microinjections of saline or DOI into the PVN, followed by BVE. RESULTS:: No significant differences were observed in the values of the studied variables in the different treatments from the control group. However, when animals are treated with DOI followed by BVE there is a significant increase in relation to the BE control group in all the studied variables: MBP (114.42±7.85 vs 101.34±9.17); SBP (147.23±14.31 vs 129.39±10.70); DBP (98.01 ±4.91 vs 87.31±8.61); HR (421.02±43.32 vs 356.35±41.99); and LF/HF ratio (2.32±0.80 vs 0.27±0.32). DISCUSSION:: The present study showed that the induction of isotonic BVE did not promote alterations in MAP, HR and LF/HF ratio. On the other hand, the injection of DOI into PVN of the hypothalamus followed by isotonic BVE resulted in a significant increase of all variables. CONCLUSION:: These results suggest that serotonin induced a neuromodulation in the PVN level, which promotes an inhibition of the baroreflex response to BVE. Therefore, the present study suggests the involvement of the serotonergic system in the modulation of vagal reflex response at PVN in the normotensive rats. FUNDAMENTO:: Expansão de volume extracelular (EVEC) promove alterações da atividade simpática e parassimpática no coração e vasos sanguíneos, os quais podem ser moduladas por vias serotoninérgicas. OBJETIVO:: Avaliar o efeito da administração de salina ou agonista serotoninérgico (DOI) nos núcleos paraventriculares hipotalâmico (NPV) sobre respostas cardiovasculares após EVEC. MÉTODOS:: Foram obtidos registros da pressão arterial pulsátil, por meio da artéria femoral, para obtenção dos valores da pressão arterial média (PAM), sistólica (PAS), diastólica (PAD), frequência cardíaca (FC) e razão simpático-vagal (LF/HF) de ratos Wistar antes e após receberem microinjeções bilaterais no NPV de salina ou DOI seguida de EVEC. RESULTADOS:: Não foram observadas diferenças significativas dos valores das variáveis estudadas nos diferentes tratamentos do grupo controle. Entretanto, quando os animais são tratados com DOI seguida de EVEC ocorre aumento significativo em relação ao grupo controle com EVEC em todas as variáveis estudadas: PAM (114,42±7,85 vs 101,34±9,17), PAS (147,23±14,31 vs 129,39±10,70), PAD (98,01 ±4,91 vs 87,31±8,61), FC (421,02±43,32 vs 356,35±41,99) e LF/HF (2,32±0,80 vs 0,27±0,32). DISCUSSÃO:: O presente estudo mostrou que a indução de EVEC isotônica não promoveu alterações na PAM, PAD, PAS, FC e LF/HF. Por outro lado, os animais que receberam microinjeção de DOI no NPV seguida de EVEC apresentaram aumento significativo de todas as variáveis. CONCLUSÃO:: Esses resultados sugerem que a serotonina exerce uma neuromodulação em nivel do NPV, e essa promove uma inibição da resposta barorreflexa frente à EVEC. Assim, o presente trabalho sugere o envolvimento serotoninérgico na neuromodulação no nivel do NPV na resposta reflexa vagal em ratos normotensos.

Effects of cholinergic stimulation with pyridostigmine bromide on chronic chagasic cardiomyopathic mice.

The aim of the present study was to assess the effects of an anticholinesterase agent, pyridostigmine bromide (Pyrido), on experimental chronic Chagas heart disease in mice. To this end, male C57BL/6J mice noninfected (control:Con) or chronically infected (5 months) with Trypanosoma cruzi (chagasic:Chg) were treated or not (NT) with Pyrido for one month. At the end of this period, electrocardiogram (ECG); cardiac autonomic function; heart histopathology; serum cytokines; and the presence of blood and tissue parasites by means of immunohistochemistry and PCR were assessed. In NT-Chg mice, significant changes in the electrocardiographic, autonomic, and cardiac histopathological profiles were observed confirming a chronic inflammatory response. Treatment with Pyrido in Chagasic mice caused a significant reduction of myocardial inflammatory infiltration, fibrosis, and hypertrophy, which was accompanied by a decrease in serum levels of IFNγ with no change in IL-10 levels, suggesting a shift of immune response toward an anti-inflammatory profile. Lower nondifferent numbers of parasite DNA copies were observed in both treated and nontreated chagasic mice. In conclusion, our findings confirm the marked neuroimmunomodulatory role played by the parasympathetic autonomic nervous system in the evolution of the inflammatory-immune response to T. cruzi during experimental chronic Chagas heart disease in mice.

Opposite effects of bone marrow-derived cells transplantation in MPTP-rat model of Parkinson's disease: a comparison study of mononuclear and mesenchymal stem cells.

The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) animal model is a useful tool to study Parkinson's disease (PD) and was used in the present study to investigate the potential beneficial as well as deleterious effects of systemic bone-marrow mononuclear cell (BMMC) or mesenchymal stem cell (BM-MSC) transplantation. MPTP administration resulted in a breakdown of the blood-brain barrier and motor impairment in the open field test 24 h after surgery. Three and 7 days after receiving the lesion, the injured animals showed remaining motor impairment compared to the sham groups along with a significant loss of tyrosine hydroxylase-immunoreactive (TH-ir) cells in the substantia nigra pars compacta (SNpc). The MPTP-lesioned rats treated with BMMCs immediately after lesioning exhibited motor impairment similar to the MPTP-saline group, though they presented a significantly higher loss of TH-ir cells in the SNpc compared to the MPTP-saline group. This increased loss of TH-ir cells in the SNpc was not observed when BMMC transplantation was performed 24 h after MPTP administration. In contrast, in the MPTP animals treated early with systemic BM-MSCs, no loss of TH-ir cells was observed. BMMCs and BM-MSCs previously labeled with CM-DiI cell tracker were found in brain sections of all transplanted animals. In addition, cells expressing CD45, an inflammatory white blood cell marker, were found in all brain sections analyzed and were more abundant in the MPTP-BMMC animals. In these animals, Iba1+ microglial cells showed also marked morphological changes indicating increased microglial activation. These results show that systemic BMMC transplantation did not ameliorate or prevent the lesion induced by MPTP. Instead, BMMC transplantation in MPTP-lesioned rats accelerated dopaminergic neuronal damage and induced motor impairment and immobility behavior. These findings suggest that caution should be taken when considering cell therapy using BMMCs to treat PD. However, systemic BM-MSC transplantation that reaches the injury site and prevents neuronal damage after an MPTP infusion could be considered as a potential treatment for PD during the early stage of disease development.