The role of nicotinic receptors in the amelioration of cholinesterase inhibitors in scopolamine-induced memory deficits.

Rationale: Nicotine receptors in the brain are closely related with memory amelioration induced by cholinesterase inhibitors.
Objective: The present study was undertaken to clarify the role of nicotinic receptors in the ameliorative effects of cholinesterase inhibitors on scopolamine-induced memory deficit.
Method: Drug effects were measured using an eight-arm radial maze with four arms baited. Hippocampal theta rhythm during the radial maze task was also recorded with a polygraph system using a telemetric technique.
Results: Scopolamine (0.5 mg/kg, i.p.) caused a spatial memory deficit as well as an increase in hippocampal theta power during radial maze performance. Pilocarpine, nicotine, physostigmine, and donepezil antagonized the effects of scopolamine. The ameliorative effects of nicotine, physostigmine, and donepezil but not piocarpine on memory performance and hippocampal theta activity were reversed by mecamylamine.
Conclusion: These results indicate that nicotinic receptors have an essential role in the ameliorative effects of cholinesterase inhibitors in both scopolamine-induced memory deficit and the increase in hippocampal theta activity.