Participa??o do sistema colin?rgico central na modula??o das respostas cardiovasculares e termorregulat?rias em ratos espontaneamente hipertensos

Existem evid?ncias que a estimula??o colin?rgica central aumenta a dissipa??o de calor em ratos normotensos como consequ?ncia de altera??es cardiovasculares via modula??o da atividade barorreflexa. No entanto, n?o h? dados publicados sobre o envolvimento do sistema colin?rgico central nestas respostas em modelo experimental que apresenta altera??o da sensibilidade dos barorreceptores e d?ficit termorregulat?rio. Assim, o objetivo do presente estudo foi verificar o envolvimento do sistema colin?rgico central na modula??o das repostas cardiovasculares e termorregulat?rias durante o repouso e exerc?cio f?sico em ratos espontaneamente hipertensos (SHR). Ratos Wistar machos (n = 33) e SHR (n = 33) foram implantados com uma c?nula intracerebroventricular (icv) para inje??es de 2 ?L de fisostigmina (fis) ou solu??o salina (sal). Temperaturas da cauda (Tcauda) e corporal interna (Tint), press?o arterial sist?lica (PAS), frequ?ncia card?aca (FC) e taxa metab?lica foram registradas durante os 60 minutos em que os ratos permaneceram em repouso, bem como durante o exerc?cio f?sico at? a fadiga ap?s inje??es icv randomizadas. Na situa??o repouso, o tratamento com fis iniciou uma sucess?o de respostas cardiovasculares e termorregulat?rias que resultaram em aumento da PAS, redu??o da FC e aumento de Tcauda nos grupos Wistar e SHR. A magnitude da ativa??o desses mecanismos foi mais intensa no SHR, afetando a Tint e melhorando a dissipa??o de calor. Durante o exerc?cio f?sico, o tratamento com fis foi capaz de modular as repostas cardiovasculares promovendo aumento significativo da PAS, seguido de bradicardia reflexa em ratos SHR e Wistar. Estas respostas foram mais intensas nos ratos Wistar. N?o houve diferen?a significativa para a Tcauda e Tint no grupo SHR fis em rela??o ao grupo sal. Entretanto, fis impactou positivamente no desempenho f?sico. Em conjunto, esses resultados fornecem evid?ncias que, durante a situa??o de repouso, a estimula??o colin?rgica central modula as repostas termorregulat?rias por meio de mudan?as no sistema cardiovascular de ratos Wistar e SHR, sendo que essas respostas s?o mais acentuadas em ratos SHR impactando na dissipa??o de calor. Durante o exerc?cio f?sico, a administra??o central de fis promove altera??es no sistema cardiovascular de ratos normotensos e hipertensos. Apesar dessas altera??es n?o terem sido suficientes para ajustar as respostas termorregulat?rias em ratos SHR, impactaram positivamente no desempenho f?sico.Tese (Doutorado) ? Programa Multic?ntrico de P?s-Gradua??o em Ci?ncias Fisiol?gicas, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017.There is evidence that central cholinergic stimulation increases heat dissipation in normotensive rats through changes on the cardiovascular system via modulation of baroreceptors function. However, there is no published data regarding the involvement of the central cholinergic system in cardiovascular and thermoregulatory responses in spontaneously hypertensive rats (SHR), which are animals that possess altered baroreceptor sensitivity and thermoregulatory deficit. Therefore, the aim of this study was to verify the involvement of the central cholinergic system in cardiovascular and thermoregulatory adjustments in SHR. Male Wistar (n = 33) and SHR (n = 33) rats were implanted with an intracerebroventricular (icv) cannula for injections of 2 ?L of physostigmine (phy) or saline (sal) solution. Tail (Ttail) and internal body temperatures (Tint), systolic arterial pressure (SAP), heart rate (HR) and metabolic rate were registered during 60 minutes while the animals remained at rest and during exercise until fatigue after randomly receiving the injections. Phy treatment started a succession of cardiovascular and thermoregulatory responses that resulted in increased SAP, reduced HR and increased Ttail in both Wistar and SHR groups. The magnitude of the activation of these mechanisms seems to be more intense in SHR, even affecting the Tint, and improve heat dissipation. During physical exercise, the phy treatment was able to modulate the cardiovascular responses promoting a significant increase of SAP, followed by reflex bradycardia in SHR and Wistar rats. These responses were more intense in Wistar rats. There was no significant difference for Ttail and Tint in the SHR group, however, phy positively impacted the physical performance. Taken together, these results provide evidence that at rest the central cholinergic stimulation modulates thermoregulatory responses through changes in the cardiovascular system of Wistar and SHR rats, and SHR rats presented greater cardiovascular and thermoregulatory responses than normotensive rats after central cholinergic stimulation. During physical exercise the central administration of phy promotes adjustments in the cardiovascular system of normotensive and hypertensive rats. Although these adjustments were not sufficient to pair the thermoregulatory responses in SHR rats, they had a positive impact on physical performance