Synaptic Activation of Voltage-Gated Channels in the Dendrites of Hippocampal Pyramidal Neurons

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Abstract
Activation of dendritic voltage-gated ion channels by local synaptic input was tested by simultaneous dendrite-attached patch-clamp recordings and whole-cell somatic voltage recordings made from CA1 pyramidal neurons in hippocampal slices. Schaffer collateral stimulation elicited subthreshold excitatory postsynaptic potentials (EPSPs) that opened voltage-gated sodium and calcium channels in the apical dendrites. The EPSP-activated sodium channels opened near the peak of the EPSP, whereas low voltage-activated calcium channels opened near the EPSP peak and during the decay phase. Dendritic high voltage-activated channels required 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.