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It has been demonstrated that neural cell adhesion molecule (NCAM) is critical for the induction and maintenance of long term potentiation (LTP) in the CA1 region of rat hippocampus. In the present study, we investigated the changes in NCAM mRNA expression and NCAM protein level after the induction of LTP in vitro using the techniques of in situ hybridization and Western blot. The results showed that the number of NCAM mRNA positive labelled neurons significantly increased (76.6+/-11.5 neurons) 10 min after tetanus when the slope of fEPSP markedly increased. The level of NCAM protein also increased significantly (7.190+/-0.64 arbitrary unit/50 microg protein) 10 min after tetanus. The number of NCAM mRNA positive labelled neurons no longer changed (73.3+/-14.0) 1 h after tetanus, however, the NCAM protein level (9.031+/-0.71) at 1 h after tetanus was higher than that at 10 min after tetanus. Moreover, the NMDA receptor inhibitor AP-5, which blocked LTP, prevented the increase in NCAM mRNA expression and NCAM protein level. The results demonstrate that NCAM mRNA expression maintains a high level, whereas NCAM protein changes from a low level to a high level during induction and maintenance of LTP.

The present study examined the changes in 26S proteasome activity and the signal molecule mechanism regulating 26S proteasome activity in long term potentiation (LTP) in rat hippocampal slices. The results are as follows: 26S proteasome activity was 190+/-14.3 cpm/(100 microg.2 h) before tetanus, a significant increase in 26S proteasome activity (273+/-18.3 cpm/(100 microg.2 h) was found 10 min after tetanus, when the slope of fEPSP was markedly increased. Interestingly, 26S proteasome activity returned to baseline level (210+/-12.8 cpm/(100 microg.2 h) 60 min after tetanus. Moreover, the N-methyl-D-aspartate (NMDA) receptor inhibitor AP-5, which blocked LTP, prevented the increase in the 26S proteasome activity. The results suggest that NMDA receptors contribute to the transient increase in 26S proteasome activity during induction of LTP in the hippocampal CA1 region.

Objective: To explore the role of 19S regulator compound protein in the degradation of skeletal muscle protein in scalded rats., Methods: Wistar rats were scalded and they were randomly divided into normal and 1, 2, 3, 5, and 7 postburn day (PBD) groups with 8 rats in each group. The 19S regulator compound of skeletal muscle in scalded rats was isolated and purified with chromatography. Rabbit-anti-rat antibody IgG of 19S regulator compound was prepared conventionally. The antibody was injected to rats in injection group (I) in which 19S antibody in dose of 3 mg/kg BW was injected for two times via tail vein with 6-hour interval. The rats in I group were decapitated on 1, 2 and 3 post-injection days, respectively. The scalded rats in control group (C) were treated in the same way, except that the antibody was replaced by normal saline. The change in content of 19S regulator compound was determined by western-blot. Meanwhile, the releasing rate of tyrosine from the skeletal muscle of scalded rats was also detected by fluorescent photography., Results: 19S regulator compound with high purity was obtained. The content of 19S regulator compound in rat skeletal muscle was increased significantly after 2 PBD. But the protein degradation rate was also obviously increased on 2 PBD. The antibody of 19S compound might inhibit the enhancement of protein degradation., Conclusion: Burn injury might up-regulate the protein level of skeletal muscle 19S regulator compound, which therefore activated the protein degradation by 26S protease compound. This might be an important factor leading to postburn negative nitrogen balance.