Spontaneous activation of KATP current in rat dorsal vagal neurones.

Membrane currents were measured in dorsal vagal motoneurones (DVMN) of rat brain stem slices. One to eight minutes after establishing the whole cell configuration, a spontaneous outward current with an amplitude of 137 +/- 54 pA and a reversal potential of -79 +/- 5 mV developed in 20% of DVMN. Tolbutamide (100-200 microM) or glibenclamide (10-50 microM) reversibly abolished the spontaneous outward current whereas only a partial blockade was detected upon administration of 20 mM tetraethylammonium. In four of 12 DVMN which did not show a progressive outward current, diazoxide evoked a tolbutamide-sensitive outward current. The results indicate that DVMN have ATP-dependent K+ channels which are activated by changes in the intracellular milieu induced by diffusion via the patch pipette.