Nitric oxide alterations in cardiovascular system of rats with Parkinsonism induced by 6-OHDA and submitted to previous exercise.

Studies showed that physical exercise decreases the risk of developing Parkinson's disease (PD) as slowing its progression. Nitric oxide (NO) increases in the substantia nigra pars compacta (SNpc) of individuals with PD. However, no study has evaluated the effects of exercise on peripheral NO levels and its modulatory effects on cardiovascular dysfunctions of subjects with PD. Trained (T) or sedentary (S) animals underwent stereotactic surgery for bilateral 6-hydroxydopamine (6-OHDA) or vehicle microinfusion (Sham group). After 6 days, the animals were catheterized for baseline parameters, followed by inhibition of NOS by Nw-nitro-arginine-methyl ester (L-NAME, 10 mg/kg - i.v.). Nitrite concentration was performed in the aorta, heart, kidney, adrenal and plasma. After exercise, the animals presented resting bradycardia (6-OHDA T and Sham T). NO was increased in the aorta of 6-OHDA S, and decreased in 6-OHDA T animals. In the heart, NO was increased in Sham T compared to sedentary and decreased in 6-OHDA T relative to 6-OHDA S and Sham T animals. At the kidney, NO decrease in 6-OHDA S and Sham T when compared to Sham S and, in adrenal gland, there was a decrease in 6-OHDA T in relation to 6-OHDA S. L-NAME promoted lower increases in MAP in 6-OHDA groups. The decreases of HR were enhanced due to physical training. 6-OHDA S group presented decreased systolic arterial pressure variability, not altered by exercise. Our data showed alterations in peripheral NO in the association of exercise with Parkinsonism in the cardiovascular function.

Functional evidence of paraventricular nucleus involvement in cardiovascular and autonomic modulation in response to acute microgravity (head-down tilt) in unanesthetized rats.

Exposure to microgravity induces autonomic and vestibular disorders such as alterations in cardiovascular function. The paraventricular nucleus of the hypothalamus (PVN) is known to be an important center for integrating autonomic and cardiovascular responses as blood volume reflexes. The acute effects promoted by microgravity and PVN involvement in cardiovascular and autonomic parameters have not yet been evaluated. Male Wistar rats were anesthetized to facilitate cannulae implantation in the PVN. After 3 days of surgical recovery, femoral artery and vein catheters were implanted for direct recording of blood pressure and heart rate (HR) in conscious animals to evaluate cardiovascular and autonomic changes in an acute protocol of head-down tilt (HDT) in nonanesthetized rats. During HDT, there was an increase in mean arterial pressure (11 ± 1 mmHg, P < 0.05) and a decrease in HR (-28 ± 5 bpm, P < 0.05). Spectral analysis of systolic arterial pressure showed an increase in the low-frequency (LF) component. In addition, HDT induced a reduction in the LF component and an increase in the high-frequency (HF) component of the pulse interval (PI). PVN inhibition with muscimol reversed bradycardia and blocked the reduction of the LF and HF increases in PI during HDT. These results suggest that the PVN participates in the cardiovascular compensation during HDT, especially modulating cardiac responses.