CALCIUM CURRENTS IN PYRAMIDAL CA1 NEURONS IN-VITRO AFTER KINDLING EPILEPTOGENESIS IN THE HIPPOCAMPUS OF THE RAT

Calcium is an important second messenger which plays a role in the reg ulation of neuronal excitability and in many forms of synaptic plastic ity. In kindling epileptogenesis, a model of focal epilepsy, calcium p lays an important role. The in situ patch-clamp technique was used to record calcium currents in slices obtained from kindled rats and contr ols. We found that low-voltage-activated calcium currents, probably of dendritic origin, were larger after kindling (80%). The transient hig h-voltage-activated calcium currents were also enhanced after kindling (50% higher). The increase of the current is accompanied by a decreas e in the time constant of inactivation. The change was still present s ix weeks after the kindling stimulations were stopped. These data demo nstrate that low-voltage-activated calcium currents are involved in ep ileptogenesis. Their enhancement in the dendrites will boost synaptic depolarization and result in enhanced calcium influx, which is critica lly dependent on the specific activation pattern. Copyright (C) 1996 I BRO.