Nicotine inhibits hippocampal and striatal acetylcholinesterase activities, and demonstrates dual action on adult neuronal proliferation and maturation

AimThe present study investigated the effects of nicotine on acetylcholinesterase (AChE) activities in the hippocampus and striatum; and on immunoreactivity of certain neurogenic markers in the dentate gyrus (DG) of the hippocampus.MethodsMale rats were given daily subcutaneous injections of nicotine at doses of 0.25, 2 or 4 mg/kg body weight for 28 days. Animals were euthanized by cervical dislocation at the end of administration. Brains were excised and processed for histochemical demonstration of AChE and immunohistochemical studies of Ki67, GFAP and NSE.ResultsThere was significant decrease (P < 0.001) in AChE positive cells in the hippocampus and striatum following 2 and 4 mg/kg nicotine but not at 0.25 mg/kg. Nicotine treatment at 0.25 and 4 mg/kg significantly decrease (P < 0.05) immunoreactivity of Ki67 and NSE in DG. Contrastingly, 2 mg/kg nicotine did not alter Ki67 immunoreactivity but rather significantly increased (P < 0.05) NSE immunoreactivity in DG compared to control.ConclusionThis study suggests that nicotine may inhibit AChE activities in the brain, thereby having a direct or indirect influence on prevention of central acetylcholine degradation, as well as either improve or retard maturation adult born neurons in DG, at different doses.