Long-term potentiation of the nucleus reuniens and entorhinal cortex to CA1 distal dendritic synapses in mice

AbstractThe 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. At the distal apical dendrites, RE evoked an initial excitatory sink followed by inhibitory sources at short (~  30 ms) and long (150–200 ms) latencies, and often showing gamma (25–40 Hz) oscillations. Both RE-evoked and spontaneous gamma-frequency local field potentials displayed the same CSD depth profile. Paired-pulse facilitation (PPF) of the distal excitatory sink at 20–200 ms interpulse inte rvals was observed following RE stimulation, generally higher than that following MPP stimulation. Theta-frequency burst stimulation (TBS) of RE induced input-specific long-term potentiation (LTP) at the distal dendritic CA1 synapses, accompanied by reduction of PPF. After TBS of the MPP, the MPP-CA 1 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 stim...
Source: Anatomy and Embryology - Category: Anatomy Source Type: research