D1/D5 Receptor Activation Promotes Long-Term Potentiation and Synaptic Tagging/Capture in Hippocampal Area CA2

Hippocampal area CA2 plays an important role in social memory formation. However, CA2 is characterised by plasticity-resistant Schaffer collateral-CA2 (SC-CA2) synapses and highly plastic entorhinal cortex-CA2 (EC-CA2) synapses. Despite abundant dopaminergic input, the relationship between dopamine signalling and area CA2 synaptic plasticity remains unexplored. Here, we show that SKF-38393-mediated Dopamine D1-like receptor (dopamine D1 and D5 receptors) activation differentially primes CA2 inputs in an NMDAR and protein synthesis-dependent manner. We defined an inverted-U shape relationship between SKF-38393 concentration and EC-CA2 potentiation. Additionally, we observed a priming effect on SC-CA2 plasticity with 50M SKF-38393, relieving plasticity resistance. We also demonstrated that this effect follows canonical protein kinase A (PKA) signalling. Collectively, our results show that D1R activation primes the CA2 for synaptic plasticity. Thus, we propose a link between neuropsychiatric diseases related to impaired dopamine transmission and deficits in hippocampus-dependent social memory.