Nicotinic activity layer specifically modulates synaptic potentiation in the mouse insular cortex

Nicotinic acetylcholine receptors (nAChRs) in the insular cortex play an important role in nicotine addiction, but its cellular and synaptic mechanisms underlying nicotine addiction still remain unresolved. In layer 5 pyramidal neurons of the mouse insular cortex, activation of nAChRs suppresses synaptic potentiation through enhancing GABAergic synaptic transmission via activation of beta 2-containing nAChRs in non-fast-spiking (non-FS) interneurons. However, it has not been addressed whether and how activation of nAChRs modulates synaptic plasticity in layers 3 and 6 pyramidal neurons of the insular cortex. In this study, I demonstrate that activation of nAChRs oppositely modulates synaptic potentiation in layers 3 and 6 pyramidal neurons of the insular cortex. In layer 3 pyramidal neurons, activation of nAChRs depressed synaptic potentiation induced by combination of presynaptic stimulation with postsynaptic depolarization (paired training) through enhancing GABAergic synaptic transmission via activation of beta 2-containing nAChRs in non-FS interneurons. By contrast, in layer 6 pyramidal neurons, activation of nAChRs enhanced synaptic potentiation through activating postsynaptic beta 2-containing nAChRs. These results indicate, in different layers of the mouse insular cortex, paired training-induced synaptic potentiation is oppositely regulated by activation of nAChRs which are located on GABAergic interneurons (layer 3) and on pyramidal neurons (layer 6). Thus, layer-specific modulation of synaptic potentiation may be involved in cellular and synaptic mechanisms of insular cortical changes in nicotine addiction.