Anesthetic effects on tonic and reflex renal sympathetic nerve activity in awake cats

Renal sympathetic nerve activity (RNA), arterial blood pressure (AP), and heart rate (HR) were simultaneously measured before and after administration of pentobarbital sodium (PB), chloralose (CHL), or urethan (URE) in conscious cats. We examined the time courses and magnitudes of the changes in RNA, AP, and HR over a period of 5 h under anesthesia with spontaneous or artificial respiration. In both respiratory conditions, PB initially decreased and then increased RNA, AP, and HR; CHL sustainedly increased RNA but had almost no effect on AP and HR. Under artificial respiration, URE transiently decreased RNA but had no effect on AP and HR. To examine the baroreflex response of RNA, AP was increased to 150 mmHg by norepinephrine and decreased to 65 mmHg by nitroprusside. RNA responded inversely to the alterations of AP in both awake and anesthetized states. Compared with the awake state, the inverse AP-RNA relationship curve initially shifted downward and then upward under PB, and the slope of the relation curve was initially decreased. On the other hand, under CHL the relationship curve shifted only upward, and the slope increased. Thus the anesthetic drugs affected differently and time dependently tonic and reflex renal sympathetic nerve activity in the conscious cat.