Alterations in amperometric cholinergic signals accompanied by synaptic plasticity and γ oscillations in the hippocampus-medial prefrontal cortex pathway.

OBJECTIVE Neural projections from the ventral hippocampal CA1 (vCA1) to the medial prefrontal cortex (mPFC) and from the posterior dorsal hippocampal CA1 (pdCA1) to the mPFC are important for information processing. Previous studies have revealed that two forms of long-term synaptic plasticity, long-term potentiation (LTP) and long-term depression (LTD), and γ oscillations, which are all believed to be neural bases for learning and memory in the vCA1-mPFC and the pdCA1-mPFC pathways, exhibited distinct profiles. However, the underlying mechanism is unclear. METHODS In the present study, amperometric cholinergic signals were monitored during in-vivo electrophysiological recordings of evoked extracellular postsynaptic potentials and spontaneous local field potentials. RESULTS The results demonstrated that in the vCA1-mPFC pathway, increased cholinergic currents and γ power of the amperometric cholinergic signals were accompanied by the induction of LTD and increased γ power of local field potentials, whereas, in the pdCA1-mPFC pathway, decreased cholinergic currents and increased γ power of the amperometric cholinergic signals were accompanied by the induction of LTP and increased γ power of local field potentials. CONCLUSION These findings indicated that some correlations may exist between amperometric cholinergic signals and synaptic plasticity in the hippocampus-mPFC pathway. The pattern of alterations in cholinergic signals may help to illustrate the specific properties of synaptic plasticity and γ oscillations in the vCA1-mPFC and the pdCA1-mPFC pathways.