Rhynchophylline down-regulates NR2B expression in cortex and hippocampal CA1 area of amphetamine-induced conditioned place preference rat.

N-methyl-D-aspartate receptor 2B subunit (NR2B) has an important role in the development of conditioned place preference (CPP) and psychostimulant abuse. Rhynchophylline is presently used to treat central nervous systems diseases and has a non-competitive antagonistic effect on NMDA receptors. In this study, amphetamine was administered in rats (2 mg/kg, s.c., once each day for 4 consecutive days), during which they were treated with rhynchophylline (60 mg/kg, i.p., once each day for the next 3 days). NR2B mRNA and protein expression were examined by in situ hybridization and immunohistochemistry. CPP was induced by amphetamine (2 mg/kg, s.c.) by 4th day in rats. Rhynchophylline effectively reversed the expression of amphetamine-induced CPP and itself did not produce a CPP. Amphetamine-CPP rats showed a significantly increased NR2B mRNA and protein expression in medial prefrontal cortex and hippocampal CA1 areas as compared to the control group. Rhynchophylline reversed NR2B mRNA and protein levels induced by amphetamine but rhynchophylline by itself had no effect on NR2B expression in control rats. These results indicate that rhynchophylline inhibits the expression of amphetamine-induced rewarding effect, and this action might be related to down-regulation of NR2B expression in medial prefrontal cortex and hippocampal CA1 area.