Up-regulation of nicotinic acetylcholine receptors by central-type acetylcholinesterase inhibitors in rat cortical neurons

We previously reported that donepezil, a central-type acetylcholinesterase inhibitor, showed neuroprotective action via alpha 4-and alpha 7-nicotinic acetylcholine receptors against glutamate neurotoxicity in rat cortical culture. The present study was performed to investigate whether the neuroprotective action of acetylcholinesterase inhibitors is accompanied by the alteration of expression and function of nicotinic receptors. Four days treatment with acetylcholinesterase inhibitors (10 mu M) enhanced the nicotine-induced increase of the intracellular calcium concentration. Immunoblot analysis revealed that donepezil increased both alpha 4 and alpha 7 subunit proteins. Donepezil and galanthamine increased the number of cells expressing alpha 4- and alpha 7-nicotinic receptors in immunocytochemical analysis. We examined whether up-regulation of nicotinic receptors affected the neuroprotective action of acetylcholinesterase inhibitors. Under up-regulating conditions, donepezil and galanthamine exerted neuroprotective action at lower concentrations. These results suggest that donepezil and galanthamine up-regulate nicotinic receptors in cortical neurons, and that the up-regulation of nicotinic receptors may make cortical neurons more sensitive to the neuroprotective action of donepezil and galanthamine. (c) 2005 Elsevier B.V. All rights reserved.