Denervation of Peripheral Chemoreceptors Decreases Heart Rate During Bilateral Carotid Occlusion in Unanesthetized Rats

Abstract

Bilateral carotid occlusion (BCO) has been used as a maneuver to cause global reflex activation of the sympathetic nervous system in both unanesthetized and anesthetized animals. It is known that the cardiovascular effects of BCO involve not only the baroreceptors but also the chemoreceptors. However, to our knowledge, the cardiovascular responses produced during BCO in the absence of the peripheral chemoreceptors has not been studied in unanesthetized rats. Therefore, the present study aimed to examine the responses of arterial pressure and heart rate to BCO in unanesthetized rats with selective denervation of peripheral chemoreceptors. Under ketamine/xylazine anesthesia Wistar Hannover rats were implanted with pneumatic cuffs around the common carotid arteries for BCO. Catheters were also inserted into the femoral artery and vein for blood pressure recording and drug administration (to test the effectiveness of denervation), respectively. Rats were divided into two groups: INTACT (n = 7) and chemoreceptors removed (CHEMO‐X; n = 8). In the next day, BCO was performed for 20s in unanesthetized rats. As compared to baseline condition BCO promoted, in both groups, an increase in systolic (INTACT: 133 ± 5 vs. 211 ± 8 mmHg; CHEMO‐X: 142 ± 3 vs. 210 ± 4 mmHg), diastolic (INTACT: 92 ± 5 vs. 145 ± 7 mmHg; CHEMO‐X: 100 ± 2 vs. 140 ± 3 mmHg) and mean arterial pressure (INTACT: 111 ± 5 vs. 173 ± 7 mmHg; CHEMO‐X: 119 ± 2 vs. 168 ± 3 mmHg). Of note, the increase in arterial pressure was similar in both groups; however, while BCO did not promote a change of the heart rate in the INTACT group (321 ± 9 vs. 318 ± 7 bpm), the rats from the QUIMIO‐X group displayed significant bradycardia (352 ± 7 vs. 315 ± 14 bpm). These findings indicate that the presence of the peripheral chemoreceptors did not affect the hypertensive response elicited by BCO, but their absence determined a reflex bradycardia during this occlusive maneuver. This mechanism deserves further investigation.Support or Funding InformationFAPESP (Proc. 2017/05163‐6 and 2013/20549‐7).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.