[Intrathecal midazolam attenuates renal sympathetic nerve activity in rabbits].

We hypothetized that intrathecal (IT) midazolam (M) affects renal sympathetic nerve activity (RSNA) via benzodiazepine receptors (BZR) at the spinal cord. Under alpha-chloralose anesthesia, 26 rabbits underwent surgical procedures for the cannulation to femoral artery and vein for measuring blood pressure and infusing lactated Ringer solution, respectively. Intrathecal cannulation was performed at the 7th thoracic vertebral level. RSNA was recorded from the nerve raw between the renal artery and vein using a left flank incision. In the neuraxis-intact rabbits, IT administration of low dose M (0.50%) did not affect heart rate (HR), mean arterial pressure (MAP), and integrated RSNA (IRSNA). High concentration of M (0.5%) increased HR, decreased MAP and attenuated IRSNA significantly. In the sino-aortic denervated rabbits, IT administration of 0.5% M decreased MAP and IRSNA, but intravenous 0.2 flumazenil rapidly and significantly increased MAP and IRSNA. This finding suggests that the decrease in IRSNA followed by IT M derives from BZR. In conclusion, IT high concentration of M attenuated RSNA through BZR.