Serine racemase expression in mouse cerebral cortex after permanent focal cerebral ischemia

AIM: To study the alterations of the expressions of serine racemase in C57BL/6 mouse brain after permanent focal cerebral ischemia. METHODS: The mRNA level and the protein level of serine racemase were assayed by semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and Western blot, respectively. The amount of D-serine and L-serine were measured by HPLC. RESULTS: High levels of serine racemase were constitutively expressed in the normal cortex of mouse. At early stage after middle cerebral artery occlusion (MCAO), no significant change in expression of serine racemase was observed in temporoparietal cortex in ipsila- teral hemisphere. However, delayed transient decreases of serine racemase in both mRNA and protein levels were detected from d 6 to d 10 after ischemia. Correspondingly, D-serine concentration also declined in the ipsilateral cortex during this period when compared with the D-serine level in the contralateral cortex. CONCLUSION: Delayed decreases in serine racemase expression and D-serine level occurred in the temporoparietal cortex at the late stage after focal cerebral ischemia.