Total RNA was isolated from neurons using Trizol reagents (Invitrogen Life Technologies, Carlsbad, CA, USA). RNA samples (2 μg) were reverse-transcribed to generate first-strand cDNA. After reverse transcription using TaqMan® Reverse Transcription Kits (Applied Biosystems), reverse-transcribed products were amplified with the 7900HT real-time PCR System (Applied Biosystems) using SYBR® Green PCR Master Mix (Applied Biosystems, Foster City, CA, USA) under the following conditions: 30 s at 95°C, followed by a total of 40 cycles of two temperature cycles (15 s at 95°C and 1 min at 60°C). Primer sequences were as follows: rat Nrdp1 forward: 5′-ATGGGGTATGATGTAACCCGG-3′ and reverse: 5′-GATGCAGGCGTTGCAGAAG-3′; Rat GAPDH served as endogenous control, and the primers were forward: 5′-CAATGTGTCCGTCGTGGATCT-3′; reverse: 5′-GTCCTCAGTGTAGCCCAAGATG-3′. The Ct value was calculated by the comparative ∆∆Ct method using the SDS Enterprise Database software (Applied Biosystems).