Experience-dependent Expression Of NMDA Receptor Subunit NR2B Protein In Rat Auditory Cortex

Previous studies indicated that the changes in NR2B expression paralleled with the developmental changes of synaptic plasticity, and early experience that affected developmental plasticity also delayed the decline in NR2B expression and NMDAR plasticity with age. Thus, it was supposed that NR2B subunit plays an important role in experience-dependent auditory cortex development in association with NMDAR components changes, and changes in NR2B expression would affect developmental plasticity.Using Western-Blotting and immunohistochemistry techniques, our present research studied the effects of early auditory deprivation on the age-dependent expression of NR2B protein in auditory cortex (AC), which is compared with the levels of NR2B mRNA temporally and spatially. The results suggested that NMDA receptor subunit NR2B protein plays a critical role in experience-dependent plasticity during auditory development, contributing to underlying the molecular mechanism of auditory developmental plasticity.1. Age-dependent expression of NMDA receptor subunit NR2B protein in the rat auditory cortexWe studied the expression of NMDA receptor subunit NR2B protein in auditory cortex of SD rats during postnatal development from postnatal day 1 (P1) to postnatal day 56 (P56). The results revealed: for rats in the normal group, the density of NR2B-positive neurons could be detected in the auditory cortex during development. The protein expression of NR2B was the highest at birth, then declined rapidly with atransient peak between P13 and P21. It reached the adult low level on P37 and remained until adult.The distribution pattern of NR2B protein in auditory cortex was also examined, revealing the highest density of NR2B protein in layer 2/3. During the postnatal days, the NR2B-positive cells density of layer2/3 declined greater than any other layers. 2. The effects of early auditory deprivation on the age-dependent expression model of NR2B protein in auditory cortex of SD ratsThe binaural plugging started from the onset of ear opening (P11 or P12) to the decapitation day of detection. We found that for rats in the deprived group, the whole decline trend of NR2B protein expression was similar to that in normal group, but the expression level from P14 to P28 was much lower than that in normal group, with the most significant reduction on PI4. That means the transient peak between PI3 and P21 for normal rats was decreased significantly by auditory deprivation, suggesting that the NR2B subunit associates with the auditory functional development of rats in critical period.After auditory deprivation the distribution feature didn't change much, remaining the highest density of NR2B protein in larer2/3. And compared with normal rat, the percent of reduction of auditory-deprived rat's NR2B protein in the Iayer4 of AC is higher than other layers during postnatal development.