Temperature modulation of ischemic neuronal death and inhibition of calcium/calmodulin-dependent protein kinase II in gerbils.

We used brief bilateral carotid artery occlusion in gerbils to examine the effects of temperature on ischemia-induced inhibition of calcium/calmodulin-dependent protein kinase II activity and neuronal death. In normothermic (36 degrees C) gerbils, ischemia induced a severe loss of hippocampal CA1 pyramidal neurons measured 7 days after ischemia (28.4 neurons/mm, n = 10; control density in 10 naive gerbils 262.1 neurons/mm) and a significant decrease in forebrain calcium/calmodulin-dependent protein kinase II autophosphorylation measured 2 hours after ischemia (12.9 fmol/min, n = 6; control phosphorylation in six naive gerbils 23.5 fmol/min). The effect of temperature on these indicators of ischemic damage was examined by adjusting intracerebral temperature before and during the ischemic insult. Hyperthermic (39 degrees C) gerbils showed almost complete loss of neurons in the CA1 region (3.0 neurons/mm, n = 11) and extension of neuronal death into the CA2, CA3, and CA4 regions. In addition, hyperthermia exacerbated ischemia-induced inhibition of calcium/calmodulin-dependent protein kinase II activity (4.2 fmol/min, n = 6). Hypothermia (32 degrees C) protected against ischemia-induced CA1 pyramidal cell damage (257.0 neurons/mm, n = 20) and inhibition of calcium/calmodulin-dependent protein kinase II activity (26.0 fmol/min, n = 6). Our results are consistent with the hypothesis that loss of calcium/calmodulin-dependent protein kinase II activity may be a critical event in the development of ischemia-induced cell death.