Objective To investigate the toxic damage Jn thalamic tissue mused by thrombin and whether can be reversed.Methods At different time following thrombin was infused into ventricule,the permeability and the destroyed volume of blood brain barrier (BBB),water content and ion content were measured.The animals,which saline infusion and which hirudin infusion six hours later following thrombin injection,as the control groups.Results Six hours later,BBB disruption,brain edema,Na、Ca concentrations increase and K concentration decrease were induced by thrombin.After hirudin infusion,BBB function was rehabilitated and the changes in brain water and brain ion were inhibited.Conclusion Damage to the thalamic tissue might be caused by thrombin and reversed byhirudin.