The extrusion of sodium ions from presynaptic nerve endings of rat cerebral cortex.

(Na+-K+) ATPase is present in synaptosomal preparations and it is assumed to represent the sodium-potassium pump. 10 microM-noradrenaline activates (Na+-K+) ATPase approximately 100%, but 50 microM-noradrenaline does not stimulate the rate of 22Na extrusion from synaptosomes. The results suggest that it is unlikely that the noradrenaline stimulation of (Na+-K+) ATPase is part of a feedback mechanism whereby released noradrenaline can influence the activity of the presynaptic sodium pump.