Developmental changes of transient potassium currents in large aspiny neurons in the neostriatum.

Developmental regulation of the potassium conductance is important for the maturation of neuronal excitability and the formation of functional circuitry in the central nervous system (CNS). The rapidly inactivating A-type current is a major component of the voltage-dependent outward potassium currents in the large aspiny (LA) neurons in the neostriatum. The large aspiny neurons play important roles in the function of neostriatum in physiological and pathological conditions. Whole-cell patch-clamp recording was performed on acutely dissociated neurons and brain slices to investigate the postnatal development of A-type current in the large aspiny neurons. The current density of A-type current in large aspiny neurons was the highest at postnatal 1-3 days and gradually decreased during the development with the lowest levels in adult animals. In comparison to postnatal 1-3 days, the steady-state inactivation curve shifted in depolarizing direction in mature neurons. No significant changes in the voltage dependence of steady-state activation were observed during development. Consistent with the decrease in the current density of A-type current during development, the latency to the first spike was dramatically shortened in mature large aspiny neurons. These results suggest that the decrease of rapidly inactivating A-type potassium current during development might contribute, at least in part, to the maturation of the membrane excitability of large aspiny neurons in the neostriatum.