Potassium currents in acutely isolated neurons from superficial and deep layers of the juvenile rat entorhinal cortex.

Using the whole-cell configuration of the patch-clamp technique, outward K+ currents were recorded from acutely isolated stellate cells from superficial layers, and pyramidal cells from deep layers, of the entorhinal cortex of juvenile rats. In both cell types a fast transient and a slowly inactivating outward K+ current were obtained. Whereas the fast transient current (IA) activated at potentials beyond -50 mV, the activation threshold of the slowly inactivating current (IK) was measured at -40 mV in stellate and pyramidal cells. In stellate cells a half-maximal inactivation was estimated for IA at -80.4 mV and for IK at -74.6 mV, and in pyramidal cells at -81.1 mV and -71.8 mV, respectively. IK of both cell types were reduced by tetraethylammonium (TEA) in a concentration-dependent manner. IC50 values were 0.8 mM TEA for stellate cells and 1.1 mM TEA for pyramidal cells. Superfusion of 4-aminopyridine resulted in a reduction of the amplitudes of IA and IK as well as in an acceleration of the inactivation time constants of IA. Extracellularly applied dendrotoxin did not have any effect on entorhinal cortex K+ currents. In summary, kinetic and pharmacological properties of IA as well as of IK are rather similar in superficial-layer stellate and deep-layer pyramidal cells acutely isolated from the entorhinal cortex of juvenile rats.