L-arginine attenuates ketamine-induced increase in renal sympathetic nerve activity

Background: It has been reported that ketamine produces sympathoexcitation by directly stimulating the central nervous system. It also has been shown that nitric oxide (NO) may play a role in signal transduction of the nervous system. Therefore, we hypothesized that the sympathoexcitation of ketamine may be linked to central NO formation. To test this hypothesis, we examined the effects of L-arginine, a substrate of NO formation, on renal sympathetic nerve activity (RSNA) during ketamine anesthesia. Methods: Using 45 rabbits given basal anesthesia with α-chloralose, we measured changes in heart rate, mean arterial pressure, and RSNA in response to intravenous ketamine (1 mg/kg) and investigated the effect of intravenous L-arginine and D-arginine (bolus 30 mg/kg followed by continuous 30 mg · kg^-1 · min^-1). The animals were divided into intact, sinoaortic and vagal-deafferented, and spinal cord-transected groups. Results: Ketamine caused significant increases in RSNA (172 ± 16%), heart rate (12 ± 2 beats/min), and mean arterial pressure (8 ± 1 mmHg) in the intact rabbits. Ketamine also increased RSNA in sinoaortic and vagal-deafferented rabbits, but not in spinal cord-transected rabbits. L-Arginine attenuated the ketamine-induced increase in RSNA in intact and deafferented rabbits, whereas D-arginine had no effect on RSNA. In addition, N(G)-nitro-L-arginine methyl ester, a NO synthase inhibitor, increased RSNA and the increase was attenuated by L-arginine. Conclusions: Ketamine may act centrally to increase sympathetic outflow, and the sympathoexcitation may be attenuated by increasing NO formation with L- arginine in the central nervous system.