Strain differences in baroceptor reflex in adult wistar kyoto rats

Abstract

OBJECTIVESA subset of normotensive Sprague–Dawley rats show lower baroreflex sensitivity; however, no previous study investigated whether there are differences in baroreflex sensitivity within this subset. Our study compared baroreflex sensitivity among conscious rats of this specific subtype.METHODSMale Wistar Kyoto (WKY) rats (16 weeks old) were studied. Cannulas were inserted into the abdominal aortic artery through the right femoral artery to measure mean arterial pressure (MAP) and heart rate (HR). Baroreflex gain was calculated as the ratio between change in HR and MAP variation (ΔHR/ΔMAP) in response to a depressor dose of sodium nitroprusside (SNP, 50 μg/kg, i.v.) and a pressor dose of phenylephrine (PE, 8 μg/kg, i.v.). Rats were divided into four groups: 1) low bradycardic baroreflex (LB), baroreflex gain (BG) between -1 and -2 bpm/mmHg tested with PE; 2) high bradycardic baroreflex (HB), BG < -2 bpm/mmHg tested with PE; 3) low tachycardic baroreflex (LT), BG between -1 and -2 bpm/mmHg tested with SNP and; 4) high tachycardic baroreflex (HT), BG < -2 bpm/mmHg tested with SNP. Significant differences were considered for p < 0.05.RESULTSApproximately 37% of the rats showed a reduced bradycardic peak, bradycardic reflex and decreased bradycardic gain of baroreflex while roughly 23% had a decreased basal HR, tachycardic peak, tachycardic reflex and reduced sympathetic baroreflex gain. No significant alterations were noted with regard to basal MAP.CONCLUSIONThere is variability regarding baroreflex sensitivity among WKY rats from the same laboratory.

Cardiology in Brazilian scientific journals: an overview

“…These data suggest that unloaded exercise has more beneficial effects than the loaded modality. Valenti et al [52] compared baroreflex sensitivity among a subset of normotensive Wistar Kyoto rats which show lower baroreflex sensitivity and found that approximately 37% of the rats showed a reduced bradycardic peak, bradycardic reflex and decreased bradycardic gain of baroreflex while roughly 23% had a decreased basal HR, tachycardic peak, tachycardic reflex and reduced sympathetic baroreflex gain. No significant alterations were noted with regard to basal MAP.…”

Heart rate variability during hemodialysis in patients with chronic renal disease

“…In the normotensive group, the authors reported increase in LF and decrease in HF components of HRV. This response is believed to be induced by compensatory activation of sympathetic nervous system facilitated by baroceptorreflex [13]. Conversely, in the hypotensive group it was found a decrease in LF and increase in HF components of HRV and decrease in LF/HF ratio [5].…”

“…It may be hypothesizedthat reduced sympathetic and increased parasympathetic nervous system activity and activation of the BezoldJarish, are involved in the response observed in our study. In this context, the Bezold-Jarish reflex is a sympatho-inhibitory cardio depressor reflex, which present important role in cardiovascular homeostasis [13,19].Previously, von Bezold and Hirt observed that an intravenous injection of veratrum alkaloids caused a decrease in blood pressure and heart rate, which was then named the Bezold-Jarisch reflex or cardiopulmonary reflex [21].…”

Cardiovascular Responses Induced by Catalase Inhibitior into the Fourth Cerebral Ventricle Is Changed in Wistar Rats Exposed to Sidestream Cigarette Smoke

“…The period of one day was necessary in order to allow a good recovery from the surgical procedures according to previous studies from our group. (24)(25)(26) Catheters were made of 4 cm segments of PE-10 polyethylene (Clay Adams, USA) heat bound to a 13 cm segment of PE-50. Catheters were tunneled under the skin and exteriorized at the animal's dorsum.…”

“…Catheters were tunneled under the skin and exteriorized at the animal's dorsum. (24)(25)(26) Arterial pressure and heart rate recording After surgery, the animals were kept in individual cages used in the transport to the experimental room. Animals were allowed 60 minutes to adapt to the conditions of the experimental room such as sound and illumination before starting blood pressure and heart rate recording.…”