Acetylcholine reduces net outward currents measured in vivo with single electrode voltage clamp techniques in neurons of the motor cortex of cats.

Effects of acetylcholine (ACh) on membrane currents of cells of the motor cortex were measured directly, in vivo, in awake cats using single electrode voltage clamp (SEVC) techniques. Extracellular applications (90-95 nA) of 2 M ACh for periods of 30 s or less produced significant decreases in net outward currents elicited by depolarizing commands whereas applications of saline did not. Reductions of net outward currents were also obtained after intracellular pressure injections of cyclic guanosine monophosphate (GMP)-dependent protein kinase (cGPK) mixed with 10 microM cyclic GMP.