Nimodipine Prevents Hyperglycemia-Induced Cerebral Acidosis in Middle Cerebral Artery Occluded Rats

Abstract

The effects of acute moderate hyperglycemia on local cerebral pH (LCpH) and local cerebral blood flow (LCBF) were studied in rats infused with glucose before middle cerebral artery (MCA) occlusion, and compared with findings in MCA occlusion alone. The effects of nimodipine infusion on LCBF and LCpH in MCA-occluded hyperglycemic rats were also studied. LCpH and LCBF were determined simultaneously by a double-label autoradiographic technique. Hyperglycemia was induced by an intraperitoneal injection of 2 g/kg D-glucose before MCA occlusion. Nimodipine-treated rats received the drug as an intravenous infusion of 0.5 μg/kg/min starting 15 min after occlusion, and ending at decapitation 4 h postocclusion. Cortical LCpH of five structures in the MCA territory of hyperglycemic rats varied between 6.64 ± 0.04 and 6.72 ± 0.02 (means ± SEM). These values were significantly lower than LCpH in the same ischemic structures in the control rats, which varied between 6.76 ± 0.04 and 6.82 ± 0.03 (p < 0.05 for four of five structures). Cortical LCpH of hyperglycemic nimodipine-treated rats ranged between 6.94 ± 0.02 and 7.05 ± 0.02, indicating significant elevations in LCpH (p < 0.001) compared with the untreated ischemic hyperglycemic animals. LCBF in the ischemic structures was not modified by hyperglycemia or nimodipine treatment. This suggests that nimodipine, by mechanisms other than improvement in blood flow, can prevent the enhanced cerebral tissue acidosis produced by hyperglycemia before incomplete focal ischemia.