Midazolam has a direct relaxing effect on vascular smooth muscle, but the mechanisms that this agent produces muscle relaxation are not fully understood. The current study was performed to identify the effects of the midazolam on K⁺ channels current in rabbit cerebral arterial smooth muscle cells.

Whole cell patch-clamp recording technique was used to evaluate the effects of midazolam (0.1 to 100µM) on outward K⁺ channel currents in dispersed rabbit cerebral arterial smooth muscle cells.

Outward K⁺ currents of rabbit cerebral artery smooth muscle cells were voltage-dependent. Midazolam (10, 100µM) tested significantly inhibited outward K⁺ currents in a dose-dependent manner and half-blocking concentration (IC₅₀) was 15.94µM at 60 mV.

Midazolam inhibit outward K⁺ currents of rabbit cerebral arterial smooth muscle cells. Further study will be needed to determine the effect of midazolam on calcium channel current because it is unclear if the inhibitory effect of midazolam on outward K⁺current induces vasoconstriction.