Functions Of NR2B Subunits In Synaptic Plasticity Of Mice M1 Cortex And Motor Learning And Memory

NMD A receptors (N-methyl-D-aspartic acid receptor) is a subtype of ionotropic glutamate receptors, NMDA receptors, especially its NR2B subunit plays a key role in learning and memory processes. Primary motor cortex (M1) is one of the main areas of the motor cortex, which is closely related to motor learning in rodents, M1 related skill forelimb movement have been found associated with NMDA receptors. Hasan, etc. have proved the NMDA receptor in M1 brain regions is necessary for learning-dependent synaptic plasticity and acquisition of associative learning memory in vivo. NR2B is an important subunit of NMDA receptor, it might be also important for synaptic plasticity of M1 as well as motor-related learning and memory. In this paper, we studied whether NR2B transgenetic overexpression and SiRNA down-regulation would impact the synaptic plasticity and motor-related learning and memory through molecular biological, in vitro electrophysiological and behavioral techniques. Results are as following:I. The influence of forebrain NR2B overexpression on synaptic plasticity and motor-related learning and memoryi. Total protein of NR2B subunit is up-regulated in M1 of NR2B transgenetic mice but not the NR2B subunit in membrane protein.ii. NR2B overexpression did not affect the basic emotional state and locomotive ability.iii. NR2B overexpression did not affect the forelimb skilled reaching ability and their operant conditioning.iv. NR2B overexpression had no impact on basic synaptic transmission, LTD and LTP of horizontal pathway in Ⅱ/Ⅲ layer of M1 cortex, namely long-term synaptic plasticity of this pathway haven’t been influenced by the overexpression of NR2B.II. The influence of M1 NR2B down-regulation on synaptic plasticity and motor-related learning and memoryⅰ. NR2B downregulation did not affect the basic emotion status and locomotive ability.ⅱ. NR2B downregulation interfered the forelimb skilled reaching ability significantly.ⅲ. NR2B downregulation significantly impaired the LTP of the horizontal pathway in Ⅱ/Ⅲ layers of M1 region.These results suggest that, NR2B down-regulation in M1 cortex impaired the long-term synaptic plasticity of M1 and motor-related learning and memory.