Although rapid synaptic transmission confers signal fidelity, the activity of some neuronal circuits depends on prolonged excitation or inhibition. Here we demonstrate that GABAergic granule cells in the rat olfactory bulb produce prolonged inhibition of mitral cells through a precise kinetic matching between transmitter-gated and voltage-gated channels in their dendritic membrane. A transient A-type potassium current (I(A)) specifically attenuated dendrodendritic inputs mediated by fast-acting AMPA receptors such that the excitation and subsequent inhibitory output of granule cells followed the prolonged kinetics of their NMDA receptors. Altering the weights of the AMPA and NMDA receptor-mediated inputs by modulating I(A) provides a mechanism to regulate the timing of inhibition according to the demands on the bulb network.
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