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 β2-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 β2-containing nAChRs in non-FS interneurons. By contrast, in layer 6 pyramidal neurons, activation of nAChRs enhanced synaptic potentiation through activating postsynaptic β2-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.
Keywords: interneuron; long-term potentiation; nicotinic acetylcholine receptor; pyramidal neuron; synaptic transmission.
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