Although the interleukin-1␤ converting enzyme (ICE)/CED-3 family of proteases has been implicated recently in neuronal cell death in vitro and in ovo, the role of specific genes belonging to this family in cell death in the nervous system remains unknown. To address this question, we examined the in vivo expression of one of these genes, Ice, after global forebrain ischemia in gerbils. Using RT-PCR and Western immunoblot techniques, we detected an increase in the mRNA and protein expression of ICE in hippocampus during a period of 4 d after ischemia. Chromatin condensation was observed in CA1 neurons within 2 d after ischemia. Internucleosomal DNA fragmentation and apoptotic bodies were observed between 3 and 4 d after ischemia, a period during which CA1 neuronal death is maximal. In nonischemic brains, ICE-like immunoreactivity was relatively low in CA1 pyramidal neurons but high in scattered hippocampal interneurons. After ischemia, ICE-like immunoreactivity was not altered in these neurons. ICE-like immunoreactivity, however, was observed in microglial cells in the regions adjacent to the CA1 layer as early as 2 d after ischemic insult. The increase in ICE-like immunoreactivity was robust at 4 d after ischemia, a period that correlates with the DNA fragmentation observed in hippocampal homogenates of ischemic brains. These results provide the first evidence for the localization and induction of ICE expression in vivo after ischemia and suggest an indirect role for ICE in ischemic damage through mediation of an inflammatory response.

p38 MAPK has been implicated in the regulation of promflammatory cytokines and apoptosis in vitro. To understand its role in neurodegeneration, we determined the time course and localization of the dually phosphorylated active form of p38 MAPK in hippocampus after global forebrain ischemia. Phosphorylated p38 MAPK and mitogen-activated protein kinase-activated protein 2 activity increased over 4 days after ischemia. Phosphorylated p38 MAPK immunoreactivity was observed in microglia in regions adjacent to, but not in, the dying CAl neurons. In contrast, neither c-Jun N-terminal kinase 1 nor p42/p44M~activity was altered after ischemia. These results provide the first evidence for localization of activated p38 MAPK in the CNS and support a role for p38 MAPK in the microglial response to stress.

The reduction of glycolysis by hypoglycemia or the glucose analog 2-deoxy-D-glucose (2DG) stimulates compensatory sympathetic alterations of metabolism. Considerable attention has been focused on the hypothalamus as the probable locus of requisite metabolic signal detection. We report, however, that unanesthetized chronically decerebrate rats are capable of exhibiting sympathoadrenal hyperglycemia in response to the metabolic challenge presented by 2DG. This findings demonstrates that the forebrain is not necessary for glucoprivic stimulation of this reflex. Since cervical cord transection has been shown to eliminate hyperglycemia induced by 2DG, we conclude that the caudal brainstem contains an essential part of the neural mechanism which both detects metabolic need and ameliorates that need through the release of stored fuels.

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Functional neural mapping by 14C-deoxyglucose autoradiography in adult rats has shown that increases in neural metabolic rate that are coupled to increased neurophysiological activity are more evident in axon terminals and dendrites than neuron cell bodies. Regions containing architectonically well-defined concentrations of terminals and dendrites (neuropil) have high metabolic rates when the neuropil is physiologically active. In neonatal rats, however, we find that regions containing well-defined groupings of neuron cell bodies have high metabolic rates in 14C-deoxyglucose autoradiograms. The striking difference between the morphological appearance of 14C-deoxyglucose autoradiograms obtained from neonatal and adult rats is probably related to developmental changes in morphometric features of differentiating neurons, as well as associated changes in type and locus of neural work performed.