Abstract
BackgroundCigarette exposure increases brain oxidative stress. The literature showed that increased brain oxidative stress affects cardiovascular regulation. However, no previous study investigated the involvement of brain oxidative stress in animals exposed to cigarette and its relationship with cardiovascular regulation. We aimed to evaluate the effects of central catalase inhibition on baroreflex and cardiovascular responses in rats exposed to sidestream cigarette smoke (SSCS).MethodsWe evaluated males Wistar rats (320-370 g), which were implanted with a stainless steel guide cannula into the fourth cerebral ventricle (4th V). Femoral artery and vein were cannulated for mean arterial pressure (MAP) and heart rate (HR) measurement and drug infusion, respectively. Rats were exposed to SSCS during three weeks, 180 minutes, 5 days/week (CO: 100-300 ppm). Baroreflex was tested with a pressor dose of phenylephrine (PHE, 8 μg/kg, bolus) to induce bradycardic reflex and a depressor dose of sodium nitroprusside (SNP, 50 μg/kg, bolus) to induce tachycardic reflex. Cardiovascular responses were evaluated before, 5, 15, 30 and 60 minutes after 3-amino-1,2,4-triazole (ATZ, catalase inhibitor, 0.001 g/100 μL) injection into the 4th V.ResultsCentral catalase inhibition increased basal HR in the control group during the first 5 minutes. SSCS exposure increased basal HR and attenuated bradycardic peak during the first 15 minutes.ConclusionWe suggest that SSCS exposure affects cardiovascular regulation through its influence on catalase activity.
Highlights
In order to verify if sidestream cigarette smoke (SSCS) exposure could affect the brain of the rats, we compared the photomicrographs between one rat exposed to fresh air (Figure 1A) and another rat exposed to SSCS (Figure 1B)
SSCS effects on basal mean arterial pressure (MAP) and heart rate (HR) There was no difference between rats exposed to fresh air and rats exposed to SSCS regarding basal MAP (Control group: 114 ± 3 mmHg vs. SSCS group: 109 ± 2 mmHg; p = 0.78) and HR (Control group: 308 ± 16 bpm vs. SSCS group: 328 ± 11 bpm; p = 0.6)
Effect of vehicle injection into the 4th V According to Table 1, injection of vehicle (0.9% NaCl) into the 4th V did not affect basal MAP and HR, tachycardic and bradycardic peak, HR range, Sympathetic baroreflex gain (SBG) and parasympathetic baroreflex gain (PBG) in Wistar rats exposed to fresh air
Summary
The literature showed that increased brain oxidative stress affects cardiovascular regulation. No previous study investigated the involvement of brain oxidative stress in animals exposed to cigarette and its relationship with cardiovascular regulation. We aimed to evaluate the effects of central catalase inhibition on baroreflex and cardiovascular responses in rats exposed to sidestream cigarette smoke (SSCS). Cigarette smoke is classified into two categories, the mainstream smoke usually inhaled by active smokers, and the sidestream smoke emitted from a cigarette and inhaled by so-called “passive smokers”. Among the negative effects of ROS we may include lipid peroxidation, which impairs the cell function, while low physiological levels of H2O2 is able to act as a classical intracellular signalling molecule regulating kinase-driven pathways [9]
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