Sympathetic responses during renal artery occlusion are altered by anesthesia

Abstract

Sympathetic hyperactivity contributes to stenotic renovascular hypertension. Transient or prolonged reduction in renal perfusion or renal artery occlusion activates renal sensory fibers to alter renal hemodynamics. Electrical stimulation of these fibers increases sympathetic nerve activity (SNA) and arterial blood pressure (ABP). Recently, we demonstrated that anesthetic agents differentially impact renal afferent sensitivity to mechano- and/or chemical-stimuli, including acute renal artery occlusion. The purpose of the present study was to assess the extent by which anesthesia affects efferent sympathetic reflex responses to renal artery occlusion. Renal, splanchnic, and lumbar SNA were measured during transient renal artery occlusion (3 min) in male and female Sprague-Dawley rats (250-400g) using unanesthetized decerebrate preparations, Inactin, isoflurane, or urethane anesthesia. Baseline ABP was significantly higher for decerebrate (122±8 mmHg) and urethane (133±6 mmHg) groups versus Inactin (78±3 mmHg) and isoflurane (95±4 mmHg; p=0.0001). Within the initial 30 seconds, renal artery occlusion decreased mean ABP in decerebrate (Δmean ABP= -13±3 mmHg; n=8; 5M, 3F), Inactin (Δmean ABP= -7±1 mmHg; n=11; 6M, 5F), urethane (Δmean ABP= -19±4 mmHg; n=11; 6M, 5F), and Isoflurane (Δmean ABP= -6±3 mmHg; n=10; 5M, 5F) groups. SNA was differentially altered during renal artery occlusion. Renal SNA significantly increased in the decerebrate (149±24%), Inactin (130±9%), and urethane (144±24%) groups relative to baseline but was significantly reduced in the isoflurane group (79±2%). Splanchnic SNA was similarly increased in decerebrate (130±12%), Inactin (150±23%), and urethane (147±19%) groups yet was significantly reduced in the isoflurane group (79±4%) compared to baseline. In marked contrast, renal artery occlusion decreased lumbar SNA in all groups (Decerebrate: 68±7%; Inactin: 67±5%; urethane: 58±3%; and Isoflurane: 63±7%. In conclusion, anesthesia differentially influences SNA and ABP responses during renal artery occlusion. In the majority of groups, arterial occlusion a differential SNA response characterized by increased renal and splanchnic SNA but decreased lumbar SNA. Isoflurane anesthesia attenuated sympathoexcitation across all groups.