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

Hippocampal gamma oscillations, as a form of neuronal network synchronization, are speculated to be associated with learning, memory and attention. Nicotinic acetyleholine receptor alpha 7 subtypes (alpha 7-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 a7-nAChRs in hippocampal gamma oscillations. Here, we examined the effects of selective alpha 7- and non-alpha 7-nAChR antagonists oil tetanic gamma oscillations in rat hippocampal slices. We found that brief tetanic stimulation-induced gamma oscillations (30-80 Hz) and pharmacological blockade of a7-nAChRs using the relatively selective alpha 7-nAChR antagonists, rnethyllycaconitine (10 or 100 nM) or a-bungarotoxin (10 nM), significantly reduced the frequency spectrum power, the number of spikes, and burst duration of evoked gamma oscillations. Neither mecamylamine nor dihydro-beta-erythroidine, which are selective antagonists of non-alpha 7-nAChRs, demonstrated significant effects on tetanic gamma oscillations. Nicotine exposure promotes hippocampal gamma oscillations in a methyllycaconitine-sensitive manner. It is concluded that alpha 7-nAChRs in hippocampal slices play important roles in regulation of gamma oscillations, thus potentially helping to explain roles of nAChRs in cognitive functions such as learning, memory and attention. (c) 2005 Elsevier Ltd. All rights reserved.