Interneurons hyperpolarize pyramidal cells along their entire somatodendritic axis.

Although GABAergic interneurons are the main source of synaptic inhibition in the cortex, activation of GABA(A) receptors has been shown to depolarize specific neuronal compartments, resulting in excitation. By using a noninvasive approach to monitor the effect of individual interneurons on the pyramidal cell population, we found that rat hippocampal interneurons hyperpolarized pyramidal cells irrespective of the location of their synapses along the somato-dendritic axis.