Electrophysiological properties of neurones in cultures from postnatal rat dentate gyrus

Electrophysiological properties of neurofilament-positive neurones in dissociated cell cultures were prepared at postnatal days 4–5 from rat dentate gyrus and studied using the whole-cell patch-clamp technique. These cells expressed a fast-inactivating, 0.5 M tetrodotoxin-sensitive Na⁺ current; a high-voltage-activated (HVA) Ca²⁺ current, which was 30 M Cd²⁺- and partially 2 M nicardipine-sensitive; and an inward rectifier current, which was sensitive to extracellularly applied 1 mM Cs⁺. The outward current pattern was composed of a delayed rectifier-like outward current sensitive to 20 mM tetraethylammonium (TEA) and a fast-inactivating, Ca²⁺-dependent outward current. This transient Ca²⁺-dependent K⁺ outward current was identified by a subtraction procedure. K⁺ currents recorded under conditions of blocked Ca²⁺ currents (after rundown of the HVA Ca²⁺ current or blocked by extracellularly applied Cd²⁺) were subtracted from control currents. By comparison with the current pattern of identified dentate granule cells, it is concluded that the investigated cell type originated from interneurones or projection neurones of the dentate hilus.