Exercise training improves vascular reactivity in ovariectomized rats subjected to myocardial infarction.

The aim of this study was to evaluate the effects of exercise training (ET) on the aortic vascular reactivity of ovariectomized and infarcted rats. The animals were divided into 5 groups: Control, Ovariectomized + SHAM sedentary (OVX+SHAMSED), OVX+SHAM and ET (OVX+SHAMET), OVX + Myocardial Infarction sedentary (OVX+MISED), and OVX + MI and ET (OVX+MIET). ET protocol (60 minutes/day, 5x/week) in a motorized treadmill began 15 days after MI and lasted 8 weeks. The endothelium-dependent and endothelium-independent vascular reactivity were evaluated as well as the role of the reactive oxygen species (ROS). Superoxide and nitric oxide (NO) production were analyzed in situ using DHE and DAF-2 fluorescence, respectively. The expression of gp91phox and of the antioxidant enzymes were evaluated by western blotting in the thoracic aorta samples. MI promoted a significant increase in the contractile response and impaired endothelium-mediated relaxation. However, ET prevented the impairment in the vascular reactivity in MI animals. In addition, the protein expression of gp91phox and superoxide production increased and the NO production decreased in the OVX+MISED group but not in the OVX+MIET group. Therefore, ET improves vascular reactivity in MI ovariectomized rats by preventing the increase in the expression of gp91phox and the decrease in the antioxidant enzymes, resulting in a normal ROS and NO production. Thus, ET can be an effective therapeutic strategy for improving the MI-induced vascular alterations in estrogen deficiency condition.

Raphe obscurus neurons participate in thermoregulation in rats.

In mammalian, several evidences suggest that central serotonin participates in thermoregulation. Nucleus raphe obscurus (NRO), a serotonergic nucleus, has been recognized to be the source of generation of various hemodynamic patterns in different behavioral conditions, but its involvement in thermoregulation is unclear. In the present study, extracellular action potentials of NRO neurons were recorded in anesthetized rats, which were submitted to cold and warm stimuli in the tail. The firing rate of the neurons was compared before and after each stimulation. It was found that 59% of the neurons submitted to a cold stimulus trial had a significant increase in their firing frequency, while 48% of the neurons submitted to warm stimulation trial were inhibited. The opposite responses in neuronal activity of NRO units to cooling or heating suggest that these cells are involved in producing the homoeothermic vascular adaptations secondary to changes in cutaneous temperature in the rat tail.

Raphe obscurus neurons participate in thermoregulation in rats / Neurônios do núcleo obscuro da rafe participam da termorregulação em ratos

In mammalian, several evidences suggest that central serotonin participates in thermoregulation. Nucleus raphe obscurus (NRO), a serotonergic nucleus, has been recognized to be the source of generation of various hemodynamic patterns in different behavioral conditions, but its involvement in thermoregulation is unclear. In the present study, extracellular action potentials of NRO neurons were recorded in anesthetized rats, which were submitted to cold and warm stimuli in the tail. The firing rate of the neurons was compared before and after each stimulation. It was found that 59% of the neurons submitted to a cold stimulus trial had a significant increase in their firing frequency, while 48% of the neurons submitted to warm stimulation trial were inhibited. The opposite responses in neuronal activity of NRO units to cooling or heating suggest that these cells are involved in producing the homoeothermic vascular adaptations secondary to changes in cutaneous temperature in the rat tail.

A termorregulação em mamíferos envolve a participação da serotonina. O núcleo obscuro da rafe (NRO), que é serotoninérgico, participa do controle autonômico, mas seu envolvimento na termorregulação é incerto. Neste estudo, registramos potenciais de ação extracelulares de neurônios do NRO em ratos anestesiados nos quais a cauda foi submetida a estímulos de calor ou frio. A frequência de disparo dos neurônios foi comparada antes e depois dos estímulos. O grupo controle não apresentou modificação da frequência de disparo, enquanto que 59% dos neurônios registrados em animais submetidos a estímulo de frio tiveram sua frequência aumentada. Por outro lado, 48% dos animais submetidos a estímulo de calor tiveram sua frequência de disparo diminuída. As respostas opostas da frequência de disparo em neurônios de animais submetidos à estimulação com frio e calor sugere que estes neurônios estejam envolvidos na geração de respostas hemodinâmicas, que são coerentes com a termorregulação nesta espécie.