Abstract
Inhibitory interneurons play important roles in neuronal circuits, but the synaptic mechanisms that regulate excitatory input onto interneurons remain to be fully understood. We show that ATP-gated presynaptic P2X2 channels facilitate excitatory transmission onto stratum radiatum interneurons but not onto CA1 pyramidal neurons. ATP released endogenously during carbachol-induced oscillations facilitates excitatory synapses onto interneurons. Overall, these data provide evidence for the molecular identity, synaptic function, and interneuron synapse specificity of a presynaptic neurotransmitter-gated cation channel. The findings highlight a novel form of presynaptic facilitation for hippocampal interneurons and suggest a role for extracellular ATP in neuronal networks.