Differentiation of ketamine effects on renal nerve activity and renal blood flow in rats

Background: A biphasic pattern in the effects of increasing dose of ketamine on mean arterial blood pressure (MBP) and renal sympathetic nerve activities (RSNA) was shown in previous study. We hypothesized that if renal vascular resistance (RVR) and renal blood flow (RBF) are mainly controlled by RSNA, they will show a similar biphasic pattern under increasing doses of ketamine. Methods: 16 female Wistar rats anesthetized with urethane were studied for ketamine at 0.5, 1, 2 mg/kg, i.v. at 30 min intervals. Multifiber RSNA recording was studied in 8 rats and RBF (by electromagnetic flowmeter) and RVR were studied in the other 8 rats with intact renal nerves. Results: our results showed that although incremental doses of ketamine brought about a biphasic pattern in MBP and RSNA, the decrease in RBF and the increase in RVR went a dose-related way. Conclusions: We concluded that there was a differentiation of ketamine effects on renal nerve activity and renal blood flow in rats. The changes of RBF and RVR can not only be attributed to the effects of sympathetic nerve activities.