Low-frequency stimulation of the temporoammonic pathway induces heterosynaptic disinhibition in the subiculum.

The subiculum (Sub) is the principal target of CA1 pyramidal cells. It serves as the final relay of hippocampal output and thus mediates hippocampal-cortical interaction. In addition, the Sub receives direct input from the entorhinal cortex via the temporoammonic pathway. In this study, we demonstrate that low-frequency stimulation of the temporoammonic pathway results in the disinhibition of excitatory synaptic transmission at CA1-Sub synapses. We provide evidence that this disinhibition is mediated by an NMDA receptor-dependent long-term depression (LTD) of GABAergic inhibition. This mechanism might bear physiological significance for the stabilization and processing of mnemonic information at hippocampal output synapses and underpins the functional role of hippocampal-entorhinal interaction in memory formation.