Dendritic conductances have previously been shown to boost excitatory postsynaptic potentials (EPSPs). To determine whether this boosting translates to an increase in the efficacy for evoking action potentials, we injected barrages of EPSPs that simulate the inputs generated by a population of presynaptic cells into either the dendrite or the soma of pyramidal neurons in vitro. Although the individual dendritic and somatic EPSPs were identical, barrages delivered to the dendrite generated much higher firing rates. Boosting occurred when the simulated cells fired asynchronously and synchronously. This Na+-mediated boosting, which was manifested during repetitive firing, may compensate functionally for electrotonic attenuation of EPSPs.
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