Postischemic brain injury is affected stereospecifically by pentazocine in rats

We tested whether rats treated with the σ₁-receptor ligand, (+)- pentazocine, during transient focal ischemia would have a smaller volume of postischemic brain infarction than rats treated with the nonspecific opioid- receptor ligand (-)-pentazocine. Rats underwent focal cerebral ischemia using the filament occlusion technique for 2 h, followed by 22 h of reperfusion. Rats received (+) or (-)-pentazocine (n = 9 each group) at a dose of 2 mg · kg^-1 · h^-1 by continuous intravenous infusion from 1 h of ischemia to 22 h of reperfusion. Triphenyltetrazolium-determined infarction volume of ipsilateral striatum ([+]-pentazocine, 19 ± 4 mm³, mean ± SEM; [-]- pentazocine, 44 ± 5 mm³) and cerebral cortex ([+]-pentazocine, 26 ± 12 mm³; [-]-pentazocine, 134 ± 29 mm³) was smaller in rats treated with (+) compared with (-)-pentazocine. Infarction volume in rats treated with (-)- pentazocine was also very similar to the infarction volume in saline-treated control rats from our previous study (striatum 44 ± 4 mm³; hemisphere 136 ± 27 mm³). These data indicate that σ₁-receptors may play an important role in the mechanism of injury both in cortex and striatum after 2 h of transient focal ischemia in rat.