Contribution of Endogeus Acetylcholine to STDP Induction

The synaptic plasticity is thought to play a crucial role in learning and memory. It has been reported that the relative timing of pre- and postsynaptic activity determines the direction and extent of hippocampal synaptic changes known as spike-timing dependent plasticity (STDP). Pre-post timing where presynaptic spike precedes a post synaptic spike induces long-term potentiation (LTP). Meanwhile, cholinergic inputs are considered to be integrated with sensory inputs and to play an important role in learning and memory. Cholinergic neurons in the medial septum are projecting their terminals to hippocampal CA1 to release acetylcholine (ACh). In order to investigate the influence of endogenous ACh on STDP, pre-post timing of STDP protocol was applied under interneuron-activated CA1 network. As the results, STDP was enhanced in the presence of eserine, and this enhancement was induced by the muscarinic and nicotinic activation not only on pyramidal neuron but also on interneurons. These findings suggest that ACh plays a critical role as a modulator for synaptic plasticity in hippocampal CA1 network.