Role of α7-nicotinic acetylcholine receptors in tetanic stimulation-induced γ oscillations in rat hippocampal slices

Hippocampal γ oscillations, as a form of neuronal network synchronization, are speculated to be associated with learning, memory and attention. Nicotinic acetylcholine receptor α7 subtypes (α7-nAChRs) are highly expressed in hippocampal neurons and play important roles in modulating neuronal function, synaptic plasticity, learning and memory. However, little is known about the role of α7-nAChRs in hippocampal γ oscillations. Here, we examined the effects of selective α7- and non-α7-nAChR antagonists on tetanic γ oscillations in rat hippocampal slices. We found that brief tetanic stimulation-induced γ oscillations (30-80 Hz) and pharmacological blockade of α7-nAChRs using the relatively selective α7-nAChR antagonists, methyllycaconitine (10 or 100 nM) or α-bungarotoxin (10 nM), significantly reduced the frequency spectrum power, the number of spikes, and burst duration of evoked γ oscillations. Neither mecamylamine nor dihydro-β-erythroidine, which are selective antagonists of non-α7-nAChRs, demonstrated significant effects on tetanic γ oscillations. Nicotine exposure promotes hippocampal γ oscillations in a methyllycaconitine-sensitive manner. It is concluded that α7-nAChRs in hippocampal slices play important roles in regulation of γ oscillations, thus potentially helping to explain roles of nAChRs in cognitive functions such as learning, memory and attention.