AIMTo explore roles of metabotropic glutamate receptor1/5 (mGluR1/5) in the induction of brain ischemic tolerance (BIT) induced by cerebral ischemic preconditioning (CIP), influences of mGluR1/5 ligand (s)-4-carboxy-3-hydroxy- phenylglycine ((s)-4C3HPG) on the induction of BIT and expression of glial fibrillary acidic protein (GFAP) in the hippocampus were observed.

METHODSThionin staining and GFAP immunohistochemistry staining in rat 4 vessel occlusion (4VO) brain ischemic model was used. Thirty-six rats, of which bilateral vertebral arteries were occluded permanently by electrocautery, were divided into the following 4 groups: sham group; ischemic insult group, BIT group and (s)-4C3HPG group. According to dosages of (s)-4C3HPG used, the (s)-4C3HPG group, was further divided into 0.2 mg, 0.04 mg and 0.008 mg subgroups. All the rats were killed 7 d after the operation or the final ischemic treatment.

RESULTS(1) The ischemic insult for 8 min increased the histological grade (HG), decreased the pyramidal neuronal density (ND) and increased the expression of GFAP significantly (P < 0.05 vs sham) (2) The CIP prevented the above injury changes in the BIT group. (3) The protective effects of the CIP were blocked by (s)-4C3HFG, as manifested by significant increases in HG and decreases in ND in the (s)-4C3HPG group (P < 0.05 vs sham and BIT groups). The changes were proportional with the dosages of (s)-4C3HPG used.

CONCLUSION(s)-4C3HPG could block the induction of BIT induced by CIP, suggested that mGluR1/5 participate in the induction of BIT.