Voltage-gated K⁺ currents were recorded from freshly dissociated satellite glial cells wrapping around ganglion cells in mouse superior cervical ganglion (SCG) by whole-cell recordings of patch clamp techniques. Both inward and outward K⁺ currents during membrane hyperpolarization and depolarization were observed in these glial cells. The current-voltage relation of these K⁺ currents became almost linear in cells obtained more than 4 weeks after birth. The magnitude of the density of inward K⁺ currents, which were elicited during membrane hyperpolarization and were eliminated by external barium, progressively increased during the first month after birth. This developmental increase in the magnitude of inward K⁺ current density was not affected by decentralization of SCG done by transection of cervical sympathetic trunk (CST) 5 days after birth. In adult mice, the magnitude of the inward K⁺ current density decreased after chronic conduction blockade of CST by local application of tetrodotoxin. On the other hand, the magnitude of the inward K⁺ current density increased after daily intraperitoneal injection of reserpine and this increase was abolished by pre-treatment of decentralization of SCG. These results suggested that preganglionic innervation was not prerequisite for developmental increase in the inward K⁺ currents and preganglionic neuronal activity upregulates the inward K⁺ currents in adult mice. Neuronal regulation of glial K⁺ channel expression would assist in K+ clearance from periganglionic space to maintain neuronal activity.