The effect of the α₂-agonist dexmedetomidine and the N-methyl-D-aspartate antagonist S(+)-ketamine on the expression of apoptosis-regulating proteins after incomplete cerebral ischemia and reperfusion in rats

In this study, we investigated whether the neuroprotection previously seen with dexmedetomidine or S(+)-ketamine involves regulation of proapoptotic (Bax and p53) and antiapoptotic (Bcl-2 and Mdm-2) proteins. Rats were anesthetized with isoflurane. After surgical preparation of isoflurane was discontinued, animals were randomly assigned to receive fentanyl and nitrous oxide (N₂O)/oxygen plus 100 μg/kg of dexmedetomidine intraperitoneally 30 min before ischemia (n = 8), 1 mg · kg^-1 · min^-1 of S(+)-ketamine and oxygen/air (n = 8), or fentanyl and N₂O/oxygen (n = 8; control group). In all three treatment groups, incomplete cerebral ischemia (30 min) was induced by unilateral carotid artery occlusion and hemorrhagic hypotension to a mean arterial blood pressure of 30-35 mm Hg. Four hours after the start of reperfusion, the brains were removed, and the expression of apoptosis-regulating proteins was determined by using immunofluorescence and Western blot analysis. The results were compared with sham-operated animals (n = 8). After cerebral ischemia/reperfusion, the relative protein concentration of Bax was increased by 110% in control animals compared with the dexmedetomidine- and S(+)-ketamine-treated rats and by 140% compared with the sham-operated animals. In animals treated with dexmedetomidine, the expression of Bcl-2 and Mdm-2 was larger compared with control (68% and 210%, respectively) or shamoperated (110% and 180%, respectively) animals. Therefore, it is possible that the neuroprotective properties of dexmedetomidine and S(+)-ketamine seen in previous studies involve ultra-early modulation of the balance between pro- and antiapoptotic proteins.