SYNAPTIC ACTIVATION OF VOLTAGE-GATED CHANNELS IN THE DENDRITES OF HIPPOCAMPAL PYRAMIDAL NEURONS

Activation of dendritic voltage-gated ion channels by local synaptic i nput was tested by simultaneous dendrite-attached patch-clamp recordin gs and whole-cell somatic voltage recordings made from CA1 pyramidal n eurons in hippocampal slices. Schaffer collateral stimulation elicited subthreshold excitatory postsynaptic potentials (EPSPs) that opened v oltage-gated sodium and calcium channels in the apical dendrites. The EPSP-activated sodium channels opened near the peak of the EPSP, where as low voltage-activated calcium channels opened near the EPSP peak an d during the decay phase. Dendritic high voltage-activated channels re quired somatic action potential generation or suprathreshold synaptic trains for activation. Dendritic voltage-gated channels are, therefore , likely to participate in dendritic integration of synaptic events.