Baroreceptor and chemoreceptor contributions to the hypertensive response to bilateral carotid occlusion in conscious mice

Abstract

This study aimed to characterize the role played by baroreceptors and chemoreceptors in the hypertensive response to bilateral carotid occlusion (BCO) in conscious C57BL mice. On the day before the experiments the animals were implanted with pneumatic cuffs around their common carotid arteries and a femoral catheter for measurement of arterial pressure. Under the same surgical approach, groups of mice were submitted to aortic or carotid sinus denervation or sham surgery. BCO was performed for 30 or 60 s, promoting prompt and sustained increase in mean arterial pressure and fall in heart rate. Compared with intact mice, the hypertensive response to 30 s of BCO was enhanced in aortic-denervated mice (52 ± 4 vs. 41 ± 4 mmHg; P < 0.05) but attenuated in carotid sinus-denervated mice (15 ± 3 vs. 41 ± 4 mmHg; P < 0.05). Suppression of peripheral chemoreceptor activity by hyperoxia [arterial partial pressure of oxygen (PaO2) > 500 mmHg] attenuated the hypertensive response to BCO in intact mice (30 ± 6 vs. 51 ± 5 mmHg in normoxia; P < 0.05) and abolished the bradycardia. It did not affect the hypertensive response in carotid sinus-denervated mice (20 ± 4 vs. 18 ± 3 mmHg in normoxia; P < 0.05). The attenuation of the hypertensive response to BCO by carotid sinus denervation or hyperoxia indicates that the hypertensive response in conscious mice is mediated by both baro- and chemoreceptors. In addition, aortic denervation potentiates the hypertensive response elicited by BCO in conscious mice.