QX-314 blocks the potassium but not the sodium-dependent component of the opiate response in locus coeruleus neurons.

Opiates hyperpolarize locus coeruleus neurons by simultaneously opening K+ channels and turning off a resting Na(+)-dependent inward current. Intracellularly applied QX-314 reduced the opiate current to approximately 40% of the control and the residual current did not reverse near EK, suggesting lack of a significant K+ component. Replacement of Na+ virtually abolished the residual opiate response. Thus, QX-314 blocks the K+ but not the Na(+)-dependent component of the opiate-induced outward current in LC neurons.