Dendritic mechanisms underlying rapid synaptic activation of fast-spiking hippocampal interneurons

Fast-spiking, parvalbumin-expressing basket cells (BCs) are important for feedforward and feedback inhibition. During network activity, BCs respond with short latency and high temporal precision. It is thought that the specific properties of input synapses are responsible for rapid recruitment. However, a potential contribution of active dendritic conductances has not been addressed. We combined confocal imaging and patch-clamp techniques to obtain simultaneous somatodendritic recordings from BCs. Action potentials were initiated in the BC axon and backpropagated into the dendrites with reduced amplitude and little activity dependence. These properties were explained by a high K+ to Na+ conductance ratio in BC dendrites. Computational analysis indicated that dendritic K+ channels convey unique integration properties to BCs, leading to the rapid and temporally precise activation by excitatory inputs.