Brain structure & function
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The present study investigated the short-term and long-term synaptic plasticity of excitatory synapses formed by the nucleus reuniens (RE) and entorhinal cortex (EC) on the distal apical dendrites of CA1 pyramidal cells. RE-CA1 synapses are implicated in memory involving the hippocampus and medial prefrontal cortex. Current source density (CSD) analysis was used to identify excitatory and inhibitory currents following stimulation of RE or medial perforant path (MPP) in urethane-anesthetized mice in vivo. ⋯ After TBS of the MPP, the MPP-CA1 distal dendritic synapse could manifest LTP or long-term depression, but the non-tetanized RE-CA1 synapse was typically potentiated. Heterosynaptic potentiation of the RE to CA1 distal synapses may occur after repeated activity of EC afferents, or spread of MPP stimulus currents to coursing RE afferents. The results indicate a propensity of RE-CA1 distal excitatory synapses to show PPF, LTP and gamma oscillations, all of which may participate in memory processing by RE and EC.