Biochemical markers of apoptosis in different brain regions after training

Activity of caspase-3 and content of DNA fragments with sizes 0.2-0.6 kbp and more than 4.0 kbp in the worm of the cerebellum, hippocampus and prefrontal cortex of the adult rat brain were estimated in 4 and 24 hours after the procedure of acoustic startle habituation and fear conditioning. Heterochronic changes in apoptotic markers in the examined brain structures were observed after training. Caspase-3 activity was decreased in the worm of the cerebellum and hippocampus, and DNA fragmentation was suppressed in the hippocampus and brain cortex. At the same time, both caspase activity and DNA fragmentation were increased in the hypothalamus. These results provide evidence for the involvement of apoptosis in the mechanisms of learning and memory in adult brain.     

Diabetes enhances apoptosis induced by cerebral ischemia

The aim of this study is to explore the mechanism by which diabetes exaggerates cerebral stroke and its outcome. Since ischemia can be related to not only necrosis but apoptosis as well, we compared the development of apoptosis in STZ-diabetic rats and STZ-diabetic rats subjected to occlusion of the middle cerebral artery (MCA). 24-48 hr following MCA occlusion the animals were killed, the brain removed and prepared for evaluation by several indexes of apoptosis: nucleosomal DNA fragmentation, TUNEL staining, activation of caspase-3 and alteration in the expression of Bax and Bcl2. DNA fragmentation was not detected in the cortex of normal and diabetic animals, but was evident following MCA occlusion in diabetic rats. Bax expression was increased in the cortex of normal rats following MCA occlusion and this expression was further increased in the cortex of MCA occluded diabetic rats. Bcl2 expression was not changed in any of the groups. In the hippocampus, DNA fragmentation was not evident in control rats but was observed in diabetic rats. Ischemic injury did not enhance DNA laddering in diabetic animals. The expression of Bax was increased in diabetic rats but was not increased following MCA occlusion. Bcl2 expression was not changed by ischemia in any of the animal models. These data suggest that diabetes may enhance the development of stroke via increased cortical apoptotic activity but this was not additive in the hippocampus following ischemic injury.     

Superoxide Dismutase, Catalase, and Glutathione Peroxidase Activities in Copper/Zinc-Superoxide Dismutase Transgenic Mice

Copper/zinc-superoxide dismutase (CuZn-SOD) transgenic mice overexpress the gene for human CuZn-SOD. To assess the effects of the overexpression of CuZn-SOD on the brain scavenging systems, we have measured the activities of manganese-SOD (Mn-SOD), catalase, and glutathione peroxidase (GSH-Px) in various regions of the mouse brain. In nontransgenic mice, cytosolic CuZn-SOD activity was highest in the caudate-putamen complex; this was followed by the brainstem and the hippocampus. The lowest activity was observed in the cerebellum. In transgenic mice, there were significant increases of cytosolic CuZn-SOD activity in all of these regions, with ratios varying from a twofold increase in the brainstem to 3.42-fold in the cerebellum in comparison with nontransgenic mice. Particulate Mn-SOD was similarly distributed in all brain regions, and its levels also were significantly increased in superoxide dismutase (SOD)-transgenic mice. In the brains of nontransgenic mice, cytosolic catalase activity was similar in all brain regions except the cortex, which showed less than 50% of the activity observed in the other regions. In transgenic mice, cytosolic catalase activity was significantly increased, with the cortex showing the greatest changes (133%) in comparison with nontransgenic mice. The smallest increases were observed in the hippocampus (34%). In contrast to what was observed for SOD and catalase, there were no significant changes in cytosolic GSH-Px activity in any of the brain regions examined. The present results indicate that, in addition to displaying marked increases in the levels of brain CuZn-SOD activity, SOD-transgenic mice also exhibit increases in other enzymes that scavenge oxygen-based radicals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Brain Region–Specific Alterations in the Gene Expression of Cytokines,Immune Cell Markers and Cholinergic System Components during Peripheral Endotoxin–Induced Inflammation

Inflammatory conditions characterized by excessive peripheral immune responses are associated with diverse alterations in brain function, and brain-derived neural pathways regulate peripheral inflammation. Important aspects of this bidirectional peripheral immune–brain communication, including the impact of peripheral inflammation on brain region–specific cytokine responses, and brain cholinergic signaling (which plays a role in controlling peripheral cytokine levels), remain unclear. To provide insight, we studied gene expression of cytokines, immune cell markers and brain cholinergic system components in the cortex, cerebellum, brainstem, hippocampus, hypothalamus, striatum and thalamus in mice after an intraperitoneal lipopolysaccharide injection. Endotoxemia was accompanied by elevated serum levels of interleukin (IL)-1β, IL-6 and other cytokines and brain region–specific increases in Il1b (the highest increase, relative to basal level, was in cortex; the lowest increase was in cerebellum) and Il6 (highest increase in cerebellum; lowest increase in striatum) mRNA expression. Gene expression of brain Gfap (astrocyte marker) was also differentially increased. However, Iba1 (microglia marker) mRNA expression was decreased in the cortex, hippocampus and other brain regions in parallel with morphological changes, indicating microglia activation. Brain choline acetyltransferase (Chat ) mRNA expression was decreased in the striatum, acetylcholinesterase (Ache) mRNA expression was decreased in the cortex and increased in the hippocampus, and M1 muscarinic acetylcholine receptor (Chrm1) mRNA expression was decreased in the cortex and the brainstem. These results reveal a previously unrecognized regional specificity in brain immunoregulatory and cholinergic system gene expression in the context of peripheral inflammation and are of interest for designing future antiinflammatory approaches.     

Novel Kv3 glycoforms differentially expressed in adult mammalian brain contain sialylated N-glycans.

The N-glycan pool of mammalian brain contains remarkably high levels of sialylated N-glycans. This study provides the first evidence that voltage-gated K+ channels Kv3.1, Kv3.3, and Kv3.4, possess distinct sialylated N-glycan structures throughout the central nervous system of the adult rat. Electrophoretic migration patterns of Kv3.1, Kv3.3, and Kv3.4 glycoproteins from spinal cord, hypothalamus, thalamus, cerebral cortex, hippocampus, and cerebellum membranes digested with glycosidases were used to identify the various glycoforms. Differences in the migration of Kv3 proteins were attributed to the desialylated N-glycans. Expression levels of the Kv3 proteins were highest in cerebellum, whereas those of Kv3.1 and Kv3.3 were much lower in the other 5 regions. The lowest level of Kv3.1 was expressed in the hypothalamus, whereas the lowest levels of Kv3.3 were expressed in both thalamus and hypothalamus. The other regions expressed intermediate levels of Kv3.3, with spinal cord expressing the highest. The expression level of Kv3.4 in the hippocampus was slightly lower than that in cerebellum, and was closely followed by the other 4 regions, with spinal cord expressing the lowest level. We suggest that novel Kv3 glycoforms may endow differences in channel function and expression among regions throughout the central nervous system.     

Differential effects of DSP-4 administration on regional brain norepinephrine turnover in rats

The effects of DSP-4 on brain NE levels and turnover in rats were investigated in six brain regions: cortex, hippocampus, cerebellum, brainstem, hypothalamus and locus coeruleus. Administration of 50 mg/kg of DSP-4 significantly decreased NE levels in all brain regions; greatest reductions occurred in the cortex (86% decrease) and in the hippocampus (91% decrease). Doses of DSP-4 less than 50 mg/kg did not significantly lower NE levels in other brain regions, except within the cerebellum. Levels of the NE metabolite 3-methoxy, 4-hydroxyphenylethylene glycol sulfate (MHPG-S04) declined in parallel with those of NE, except within the brainstem and the locus coeruleus. NE turnover, expressed as the ratio of the MHPG-S04 concentration to that of NE, was higher in the cortex and hippocampus than other regions in control animals, and NE turnover significantly increased only in these two areas after the administration of 50 mg/kg of DSP-4 (p less than 0.01). There were no significant changes in the levels of dopamine and a significant decrease of serotonin only in the striatum. These results indicate that DSP-4 is a neurotoxin with a strong predilection for noradrenergic neurons, that its effects vary according to brain region and that its administration increases NE turnover in those brain regions showing the greatest depletion of NE.     

Effect of hypoxia on DNA fragmentation in different brain regions of the newborn piglet

DNA fragmentation has been studied in different regions of the newborn piglet brain following different times of normobaric hypoxia (5% O(2), 95% N(2)). After 1 hr of hypoxia, fragmented DNA was observed in cerebellum, cortex, hippocampus, and striatum but not in hypothalamus. More fragmentation occurred in these areas of the brain when the animals were kept under hypoxia for times up to 8 hr 45 min. When the animals were submitted to hypoxia for two and a half hours, integrity of DNA was recovered respectively after 3 hr of exposure to the ambient atmosphere in hippocampus and striatum, but 4 hr of recovery were necessary for cerebellum and cortex. These results are discussed in terms of the consequences of neonatal hypoxia and apnea for newborn infants and economical impact for farm animals.     

Pentylenetetrazole kindling induces caspase-3 activation in rat brain

Pentylenetetrazole kindling (but not a single pentylenetetrazole injection) induced caspase-3 activation in the cerebral cortex, hippocampus, and cerebellum of rats as well as neurodegeneration in the hippocampus. The number of neurons in the CA3 subfield of the hippocampus decreased significantly, whereas no apoptotic nuclei could be detected. The results support a possible non-apoptotic involvement of caspase-3 in brain plasticity.     

Lentivirus-mediated microRNA-26a-modified neural stem cells improve brain injury in rats with cerebral palsy

This study is launched to investigate the effect of lentivirus-mediated microRNA-26a (miR-26a)-modified neural stem cells (NSCs) in brain injury in rats with cerebral palsy (CP). The successfully constructed miR-26a lentivirus expression vector and empty vector virus were used to modify NSCs. The model of CP with ischemia and anoxia was established in rats. NSCs and miR-26a-NSCs were stereoscopically injected into the cerebral cortex of the modeled rats, respectively. The survival and migration of NSCs infected with recombinant lentivirus expressing green fluorescence in vivo was observed under a light microscope. The neurobehavioral functions, morphology, and ultrastructure of cerebral cortex and hippocampus, apoptosis of brain cells, expression of apoptosis-related protein caspase-3 and Bax, together with the expression of the glial fibrillary acidic protein (GFAP) in cerebral cortex and hippocampus were determined. Expression of miR-26a in NSCs infected with plVTHM-miR-26a increased significantly. After NSCs transplantation, the neurobehavioral status of CP rats was improved, the degree of brain pathological injury was alleviated, the apoptotic index of cells in cerebral cortex and hippocampus and the expression of the apoptotic protein (caspase-3 and Bax) were decreased, the expression of GFAP were significantly decreased. After miR-26a-NSCs transplantation, these aforementioned results further improved or decreased. Our study suggests that miR-26a-modified NSCs mediated by lentivirus can improve brain injury, inhibit apoptosis of brain cells and activation of astrocytes in CP rats.     

Distribution and Developmental Regulation of Metabotropic Glutamate Receptor 7a in Rat Brain

Abstract: To determine the regional and cellular distribution of the metabotropic glutamate receptor mGluR7a, we used rabbit anti-peptide polyclonal-targeted antibodies against the C-terminal domain of mGluR7a. Here we report that immunocytochemistry at the light-microscopic level revealed that mGluR7a is widely distributed throughout the adult rat brain, with a high level of expression in sensory areas, such as piriform cortex, superior colliculus, and dorsal cochlear nucleus. In most brain structures, mGluR7a immunoreactivity is characterized by staining of puncta and fibers. However, in some regions, including the locus ceruleus, cerebellum, and thalamic nuclei, both cell bodies and fibers are immunopositive. The changes in levels of mGluR7a during development were investigated with immunoblotting and immunocytochemical analysis. Immunoblot analysis revealed that the levels of mGluR7a are differentially regulated across brain regions during postnatal development. In cortical regions (hippocampus, neocortex, and olfactory cortex), mGluR7a levels were highest at postnatal day 7 (P7) and P14, then declined in older rats. In contrast, mGluR7a levels were highest at P7 in pons/medulla and cerebellum and decreased markedly between P7 and P14. In these regions, mGluR7a immunoreactivity was at similar low levels at P14 and P21 and in adults. Immunocytochemical analysis revealed that staining for mGluR7a was exceptionally high in fiber tracts in P7 animals relative to adults. Furthermore, the pattern of mGluR7a immunoreactivity in certain brain structures, including cerebellum, piriform cortex, and hippocampus, was significantly different in P7 and adult animals. In summary, these data suggest that mGluR7a is widely distributed throughout the rat brain and that this receptor undergoes a dynamic, regionally specific regulation during postnatal development.     

Maternal Undernutrition During Lactation: Effect on Amino Acids in Brain Regions of Offspring

Sprague-Dawley dams were fed either a protein-calorie deficient or control diet from day 5 to day 21 after parturition. The concentrations of seven amino acids (aspartate, glutamate, gamma-aminobutyric acid, glycine, glutamine, serine, and taurine) were determined in brain regions from 17-day-old undernourished offspring and from 35-day-old rehabilitated rats. The brain regions examined were the cortex, cerebellum, corpus striatum, hippocampus, hypothalamus, brainstem, and midbrain. At 17 days of age, taurine was the amino acid with the highest concentration, whereas at 35 days glutamate had the highest concentration. This change was due to the fact that the concentration of taurine decreased significantly in all brain regions between 17 and 35 days, whereas the concentration of glutamate remained high or increased somewhat in all brain regions except the hypothalamus and brainstem. When the age-matched offspring of control and undernourished rats were compared, several interesting and significant differences were found. The concentrations of glutamate and aspartate were significantly lower (decreased 16-34%) in the cerebellum, brainstem, cortex, and midbrain in 17-day-old undernourished rats. The aspartate level was also significantly decreased in the corpus striatum and hypothalamus in 17-day-old offspring. However, the deficiencies of aspartate and glutamate were transient and reversible. In contrast, the concentration of taurine was increased in the hypothalamus (31%) and hippocampus (12-33%) at both 17 and 35 days of age and in the midbrain (17%) at 17 days. Other transient abnormalities in amino acid levels were found in undernourished offspring. The results of these experiments suggest that undernutrition during lactation causes delayed CNS development, which is manifested in altered concentrations of the neurotransmitters aspartate, glutamate, and taurine.     

Apicidin, a histone deacetylase inhibitor, induces apoptosis and Fas/Fas ligand expression in human acute promyelocytic leukemia cells.

We previously reported that apicidin arrested human cancer cell growth through selective induction of p21(WAF1/Cip1). In this study, the apoptotic potential of apicidin and its mechanism in HL60 cells was investigated. Treatment of HL60 cells with apicidin caused a decrease in viable cell number in a dose-dependent manner and an increase in DNA fragmentation, nuclear morphological change, and apoptotic body formation, concomitant with progressive accumulation of hyperacetylated histone H4. In addition, apicidin converted the procaspase-3 form to catalytically active effector protease, resulting in subsequent cleavages of poly(ADP-ribose) polymerase and p21(WAF1/Cip1). Incubation of HL60 cells with z-DEVD-fmk, a caspase-3 inhibitor, almost completely abrogated apicidin-induced activation of caspase-3, DNA fragmentation, and cleavages of poly(ADP-ribose) polymerase and p21(WAF1/Cip1). Moreover, these effects were preceded by an increase in translocation of Bax into the mitochondria, resulting in the release of cytochrome c and cleavage of procaspase-9. The addition of cycloheximide greatly inhibited activation of caspase-3 by apicidin by interfering with cleavage of procaspase-3 and DNA fragmentation, suggesting that apicidin-induced apoptosis was dependent on de novo protein synthesis. Consistent with these results, apicidin transiently increased the expressions of both Fas and Fas ligand. Preincubation with NOK-1 monoclonal antibody, which prevents the Fas-Fas ligand interaction and is inhibitory to Fas signaling, interfered with apicidin-induced translocation of Bax, cytochrome c release, cleavage of procaspase-3, and DNA fragmentation. Taken together, the results suggest that apicidin might induce apoptosis through selective induction of Fas/Fas ligand, resulting in the release of cytochrome c from the mitochondria to the cytosol and subsequent activation of caspase-9 and caspase-3.     

RATE OF ACCUMULATION OF ACETYLCHOLINE IN DISCRETE REGIONS OF THE RAT BRAIN AFTER DICHLORVOS TREATMENT

Abstract– The time course for accumulation of acetylcholine was measured in rat brain regions after treatment with 15 mg/kg, i.v., dichlorvos. With this dose of dichlorvos 84-96% of the brain cholinester-ase is inhibited within 1 min. After killing and concomitant enzyme inactivation through microwave irradiation, the acetylcholine levels were measured by pyrolysis-gas chromatography. In the brain regions studied, the striatum had the highest rate of accumulation of acetylcholine and the cerebellum had the lowest. The calculated turnover time in minutes for the regions of the brain were cerebral cortex 0.9; hippocampus 1; striatum 1.4; cerebellum 1.7; medulla-pons 2.2; midbrain 4.5; thalamus 5.6.     

Heat-Shock 70 Messenger RNA Levels in Human Brain: Correlation with Agonal Fever

Abstract: Systematic review of antemortem clinical information on randomly selected Alzheimer disease (AD) patients revealed that ∼40% of the patients had a recorded fever of ≥39.2°C at or near death. Using isolation and quantitation techniques appropriate for analysis of human brain mRNAs, we found that low levels of inducible heat-shock protein 70 (hsp70) mRNAs were present in cerebellum of afebrile AD patients and that mRNA levels were usually lower in two brain regions affected in AD, i.e., hippocampus and temporal cortex. Levels of hsp70 mRNAs were increased three- to 33-fold in cerebellum of febrile patients compared with levels in patients whose recorded temperatures were ≤37.5°C. Levels of hsp70 mRNAs were also increased in hippocampus and cortex of these febrile patients, but to a lesser extent than cerebellum. Heat-shock cognate 70 (hsc70) mRNAs were present at highest levels in afebrile cerebellum and were also present in the other brain regions. In cerebellum of patients with the highest temperatures, hsc70 mRNAs were induced severalfold over basal levels. Although there was a low and variable induction of hsc70 mRNAs in temporal cortex of these patients, there was no evidence for any induction in hippocampus. Increased heat-shock 70 mRNA levels did not correlate with hypoxia, coma, hypertension, hypoglycemia, seizures, or medication. These results indicate that a specific agonal stress, namely fever, can increase the levels of heat shock 70 mRNAs in AD brain; however, there is no evidence to suggest that affected regions of AD brain have higher overall levels of these mRNAs. Failure to obtain adequate agonal state information could result in inaccurately identifying short-term stress-related changes in postmortem brain as neuropathology characteristic of a chronic disease state.     

Cannabinoid Receptors and Modulation of Cyclic AMP Accumulation in the Rat Brain

The mechanism by which cannabinoid compounds produce their effects in the rat brain was evaluated in this investigation. Cannabinoid receptors, quantitated by [3H]CP-55,940 binding, were found in greatest abundance in the rat cortex, cerebellum, hippocampus, and striatum, with smaller but significant binding also found in the hypothalamus, brainstem, and spinal cord. Using rat brain slice preparations, we evaluated the effect of desacetyllevonantradol on basal and forskolin-stimulated cyclic AMP accumulation in the regions exhibiting the greatest cannabinoid receptor density. Desacetyllevonantradol (10 microM) reduced cyclic AMP levels in the hippocampus, frontal cortex, and striatum. In the cerebellum, however, the response to desacetyllevonantradol was biphasic with cyclic AMP accumulation being decreased at lower and increased at higher concentrations. Desacetyllevonantradol reduced cyclic AMP accumulation in isoproterenol-stimulated slices in the cortex and cerebellum, but not in the hippocampus. Cells that responded to vasoactive intestinal peptide with an increase in cyclic AMP accumulation in the hippocampus and cortex also responded to desacetyllevonantradol. The modulation of cyclic AMP accumulation by desacetyllevonantradol could be attenuated following stereotaxic implantation of pertussis toxin, supporting the involvement of a G protein in the cannabinoid response in the brain. However, other actions of cannabinoid compounds may also affect the cyclic AMP levels in brain slice preparations.     

Regional distribution of the histamine metabolite, tele-methylimidazoleacetic acid, in rat brain: effects of pargyline and probenecid

Abstract: tele -Methylimidazoleacetic acid (t-MIAA), a major brain histamine metabolite, was measured in nine rat brain regions by a gas chromatography-mass spectrometric method that also measures the precursor amine, tele -methylhistamine (t-MH). The t-MIAA concentration of cerebellum, medulla-pons, midbrain, caudate nucleus, hypothalamus, frontal cortex, hippocampus, and thalamus varied 15-fold, hypothalamus showing the highest level (2.21 nmol/g) and cerebellum the lowest (0.15 nmol/ g). The concentrations of t-MIAA and t-MH were significantly correlated in all regions except midbrain, which had relatively more t-MIAA. Probenecid did not alter whole-brain t-MIAA levels. Treatment with pargyline, an inhibitor of monoamine oxidase, lowered the t-MIAA levels in all regions.     

Antioxidant responses to chronic hypoxia in the rat cerebellum and pons

Obstructive sleep apnea (OSA) is characterized by chronic intermittent hypoxia (CIH) and sleep fragmentation and deprivation. Exposure to CIH results in oxidative stress in the cortex, hippocampus and basal forebrain of rats and mice. We show that sustained and intermittent hypoxia induces antioxidant responses, an indicator of oxidative stress, in the rat cerebellum and pons. Increased glutathione reductase (GR) activity and thiobarbituric acid reactive substance (TBARS) levels were observed in the pons and cerebellum of rats exposed to CIH or chronic sustained hypoxia (CSH) compared with room air (RA) controls. Exposure to CIH or CSH increased GR activity in the pons, while exposure to CSH increased the level of TBARS in the cerebellum. The level of TBARS was increased to a greater extent after exposure to CSH than to CIH in the cerebellum and pons. Increased superoxide dismutase activity (SOD) and decreased total glutathione (GSHt) levels were observed after exposure to CIH compared with CSH only in the pons. We have previously shown that prolonged sleep deprivation decreased SOD activity in the rat hippocampus and brainstem, without affecting the cerebellum, cortex or hypothalamus. We therefore conclude that sleep deprivation and hypoxia differentially affect antioxidant responses in different brain regions.     

Alterations in monoamine levels in discrete regions of rat brain after chronic administration of carbamazepine

Carbamazepine (25 mg/kg body weight) was administered intraperitoneally to adult male Wistar rats for 45 days and norepinephrine (NE), dopamine (DA) and serotonin (5-HT) levels were simultaneously assayed in discrete brain regions by high performance liquid chromatographic (HPLC) method. Experimental rats displayed no behavioral abnormalities. Body and brain weights were not significantly different from control group of rats. After exposure it was observed that norepinephrine levels were elevated in motor cortex (P<0.01) and cerebellum (P<0.05), while dopamine levels were decreased in these two regions (P<0.001, P<0.05). However, dopamine levels were increased in hippocampus (P<0.01). Serotonin levels were significantly decreased in motor cortex (P<0.001) and hypothalamus (P<0.001) but increased in striatum-accumbens (P<0.001) and brainstem (P<0.001). These results suggest that carbamazepine may mediate its anticonvulsant effect by differential alterations of monoamine levels in discrete brain regions particularly in motor cortex and cerebellum.     

Regional CNS Levels of Acetylcholine and Choline During Hypoglycemic Stupor and Recovery

During insulin stupor in mice, acetylcholine levels in cerebral cortex, cerebellum. brainstem, striatum, and hippocampus were unchanged from control values despite brain glucose concentrations 3-10% of normal, whereas choline levels rose 2.4-3.6-fold in all five CNS regions. Brain acetylcholine and choline levels did not change during recovery following glucose injection. The data suggest that. in hypoglycemic stupor, (1) overall rates of acetylcholine synthesis and degradation remain balanced within each of the CNS regions studied: (2) the biochemical mechanism that elevates brain choline levels is unlikely to be related only to cholinergic synaptic processes: and (3) brain choline levels need not rise for stupor to occur.     

Involvement of caspase-3-like protease in the mechanism of cell death following focally evoked limbic seizures

The cysteine protease caspase-3 may be involved in the mechanism of cell death following seizures. Using a rat model of focally evoked limbic epilepsy with continuous electroencephalography monitoring, we investigated seizure-induced changes in caspase-3 protein expression and processing, enzyme activity, and the in vivo effect of caspase-3 inhibition. Seizures were induced by intraamygdaloid injection of kainic acid (0.1 microg) and were terminated after 45 min by diazepam (30 mg/kg) administration. Animals were killed 0-72 h following diazepam administration. Levels of the 32-kDa proenzyme form of caspase-3 were unaffected by seizures. Levels of the 17-kDa cleaved (active) fragment of caspase-3 were almost undetectable in control brain, but were increased significantly at 4 and 24 h within ipsilateral hippocampus and cortex in seizure animals. Caspase-3-like protease activity was increased within the ipsilateral hippocampus at 8 and 24 h following seizures. Caspase-3 immunoreactivity was increased within the vulnerable ipsilateral CA3/CA4 subfield at 24 and 72 h following seizures and was associated predominantly, but not exclusively, with neurons exhibiting DNA fragmentation. The putatively selective caspase-3 inhibitor N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone significantly improved neuronal survival bilaterally within the hippocampal CA3/CA4 subfields following seizures. Collectively, these data suggest that caspase-3 may play a significant role in the mechanism by which neurons die following seizures.