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Background and Purpose— Thrombin-induced clots used in experimental thromboembolic stroke differ from clots forming spontaneously under clinical conditions. We investigated whether this difference influences the efficacy and outcome of thrombolytic treatment. Methods— In rats, the middle cerebral artery was occluded by intracarotid injection of fibrin-rich clots, prepared either according to established methods by adding thrombin to freshly drawn arterial blood or by spontaneous coagulation. The mechanical properties of clots were determined in vitro by elasticity and plasticity tests. One hour after embolism, thrombolysis was started by intra-arterial application of recombinant tissue plasminogen activator (rtPA) (10 mg/kg). Treatment efficacy was monitored by MR measurements of blood perfusion, apparent diffusion coefficient (ADC), T2 relaxation time and blood-brain barrier permeability, and by pictorial measurements of ATP and pH. Results— Thrombin-induced clots were classified as elastic, and spontaneously forming clots were classified as plastic. Middle cerebral artery embolism with thrombin-induced or spontaneously forming clots led to similar reduction of perfusion and ADC, but rtPA treatment efficacy differed greatly. In the spontaneously forming clot group, blood perfusion returned to or above control within 2 hours, ADC and ATP normalized, tissue pH exhibited alkalosis, and T2 and blood-brain barrier permeability did not change. In the thrombin-induced clot group, in contrast, blood reperfusion was delayed, ADC and ATP remained reduced, tissue pH was acidic, and edema developed, as reflected by increased T2 and blood-brain barrier permeability. Conclusions— rtPA-induced thrombolysis promotes rapid reperfusion and tissue recovery in animals embolized with spontaneously forming clots but not in those embolized with thrombin-induced clots. This difference is explained by the different mechanical and possibly molecular consequences of clot preparation and must be considered for the interpretation of thrombolysis experiments.

With the increasing use of mobile communication, concerns have been expressed about the possible interactions of electromagnetic radiation with the human organism and, in particular, the brain. The effects on neuronal electrical activity, energy metabolism, genomic responses, neurotransmitter balance, blood-brain barrier permeability, cognitive function, sleep, and various brain diseases including brain tumors are reviewed. Most of the reported effects are small as long as the radiation intensity remains in the nonthermal range, and none of the research reviewed gives an indication of the mechanisms involved at this range. However, health risks may evolve from indirect consequences of mobile telephony, such as the sharply increased incidence rate of traffic accidents caused by telephony during driving, and possibly also by stress reactions which annoyed bystanders may experience when cellular phones are used in public places. These indirect health effects presumably outweigh the direct biological perturbations and should be investigated in more detail in the future.

The cellular mechanisms underlying functional hyperemia--the coupling of neuronal activation to cerebral blood vessel responses--are not yet known. Here we show in rat cortical slices that the dilation of arterioles triggered by neuronal activity is dependent on glutamate-mediated [Ca(2+)](i) oscillations in astrocytes. Inhibition of these Ca(2+) responses resulted in the impairment of activity-dependent vasodilation, whereas selective activation--by patch pipette--of single astrocytes that were in contact with arterioles triggered vessel relaxation. We also found that a cyclooxygenase product is centrally involved in this astrocyte-mediated control of arterioles. In vivo blockade of glutamate-mediated [Ca(2+)](i) elevations in astrocytes reduced the blood flow increase in the somatosensory cortex during contralateral forepaw stimulation. Taken together, our findings show that neuron-to-astrocyte signaling is a key mechanism in functional hyperemia.

The effect of three metabolic inhibitors--iodoacetate, potassium cyanide, and potassium arsenate--on neuronal viability was studied in primary rat cortical and hippocampal CA1 neuronal cultures. Iodoacetate (0.1 mM) applied for 5 min to 8-day-old cultures resulted in delayed neuronal death within 3-24 h in cortical and hippocampal CA1 neurons. Neuronal degeneration was preceded by transient inhibition of energy metabolism to approximately 40% and a permanent inhibition of protein synthesis to approximately 50%. The inhibition of protein synthesis and the neuronal death were prevented by the free radical scavenger vitamin E but not by the glutamate antagonist MK-801. Removal of calcium during iodoacetate exposure could not protect against toxicity, and there was no increase of intracellular calcium concentration during and shortly after iodoacetate treatment. Cyanide and arsenate produced only partial neuronal degeneration, even at a dose of 10 mM. These observations demonstrate that brief exposure of neurons to low concentrations of iodoacetate produces a delayed type of neuronal death that is not mediated by either calcium or glutamate. The therapeutic effect of vitamin E points to a free-radical mediated injury and suggests that this type of pathology may also be involved in delayed neuronal death after transient energy depletion in vivo.

Rats were submitted to 10-min cardiac arrest, followed by resuscitation and survival for 1 day, 3 days or 1 week. Five regions of interest (CA1 and CA3 sector of hippocampus, dentate gyrus, reticular nucleus of thalamus and parietal cortex) where studied by light and electron microscopy at each of the survival times, and compared with non-ischemic control rats. Cell counts revealed delayed neuronal loss of about 30% after 3 days in both CA1 and CA3 sectors. Ischemic cell changes consisting of cytoplasmic condensation and nuclear pyknosis appeared in these regions on day 7 and --to a lesser degree-- also affected dentate gyrus, the reticular nucleus of thalamus and cerebral cortex. Ultrastructural alterations were evaluated using an ultrastructural injury catalogue. In all brain regions similar, although quantitatively differently expressed, changes occurred except ribosomal disaggregation, which was restricted to neurons of hippocampal CA1 sector on the first day after cardiac arrest. Progressive alterations included swelling of mitochondria and endoplasmic reticulum, which was most pronounced in CA1 and CA3 sectors of hippocampus, as well as chromatin aggregation and alterations of neuronal volume, which affected mainly the granule cells of dentate gyrus. Other alterations, such as osmiophilic inclusions or the formation of nuclear pore complexes, were transient with a maximum on the first day after cardiac arrest. Treatment with the free-radical scavenger alpha-phenyl-N-tert-butyl nitrone (PBN) suppressed the formation of nuclear pores but otherwise did not markedly change the morphological outcome. In comparison to previous studies of global brain ischemia induced by arterial inflow occlusion of the same duration, the present data demonstrate remarkable preservation of tissue integrity in CA1 sector but also distinct changes in brain regions considered to be resistant to ischemic injury. Morphological alterations of brain after cardiac arrest do not follow the established pattern of selective vulnerability.

Two patterns of transforming growth factor-beta1 (TGF-beta1) expression were identified in brains of normotensive rats following permanent occlusion of the middle cerebral artery (MCAO). First, a relative increase of TGF-beta1 mRNA by 37% was found at 12 h after MCAO in the ipsilateral cingulate cortex as compared to the homotopic contralateral region. The cingulate cortex is located distant from the ischemic territory. Treatment with the glutamate receptor antagonists MK-801 and NBQX did not reduce this expression (34% and 26% increase, respectively). Therefore, peri-infarct depolarization waves were probably not responsible for induction. Secondly, an increase of TGF-beta1 mRNA by 116% was found at 7 days after MCAO within infarcted tissue. This expression was not reduced by the glutamate receptor antagonists MK-801 (increase 140%) and NBQX (increase 137%), either. TGF-beta1 mRNA expression in the cingulate cortex at 12 h after MCAO is possibly mediated by neurons and astroglia and may support cell survival. Expression in the infarcted tissue at 7 days after MCAO is most likely related to the invasion of monocytes and may be involved in the downregulation of inflammatory events, in neoangiogenesis, and in formation of a glial scar around the infarct.

C57Black/6 and SV129 mice are widely used for the production of transgenic mutants in molecular stroke research but the ischemic susceptibility of these strains is influenced by differences in vascular anatomy and the responsiveness to excitotoxins and vasodilatory stimuli. To differentiate between these opposing effects on infarct size, the vascular territory of the two strains was correlated with the hemodynamic, metabolic, and morphological consequences of permanent middle cerebral artery (MCA) occlusion. The vascular anatomy was studied by latex infusion, brain infarction by vital staining, the size of the ischemic penumbra by imaging of ATP and protein synthesis, and blood flow by laser–Doppler flowmetry. In C57Black/6 mice the MCA-supplied vascular territory and the size of brain infarcts were significantly larger than in SV129 mice but the size of the penumbra and the residual blood flow in the center of the MCA-supplying territory were similar in both strains. These findings suggest that differences in infarct size in C57Black/6 and SV129 mice are determined mainly by the vascular anatomy and not by differences in collateral vascular responsiveness or excitotoxicity.

It has been suggested that tissue plasminogen activator (tPA), which is widely used for the thrombolytic treatment of stroke, exhibits neurotoxic side effects. To test this hypothesis, mice exposed to 90 min nonthrombotic middle cerebral artery thread occlusion were treated with 10 mg/kg recombinant tPA (rt-PA) at 15 min after the onset of vascular occlusion. Measurements of blood flow, infarct volume, brain swelling and neurological performance revealed faster recirculation and a significant reduction of ischemic injury in rt-PA-treated animals. These data are at variance with previous reports on tPA neurotoxicity and demonstrate, on the contrary, that tPA protects the brain even after non-thrombotic vascular occlusion.

The effects of a traumatic neocortical lesion on c-fos, junB, c-jun, MKP-1 and hsp72 expression were examined by in situ hybridization and immunocytochemistry 1-6 h following transcranial cold injury. The direct current potential was recorded in the injury-remote cortex to evaluate the role of transient direct current shifts, i.e. spreading depressions, in gene expression. In 14 out of 21 injured rats, spreading depression-like depolarizations of the direct current potential were noticed, which were accompanied by a transient decrease in electroencephalographic activity and increase in laser Doppler flow. In seven injured animals, no spontaneous spreading depressions were seen. In animals without spreading depressions, only a short-lasting response of c-fos, junB, c-jun and MKP-1 messenger RNAs as well as c-Fos protein was bilaterally found in the piriform cortex, and--with ipsilateral dominance--the dentate gyrus and hippocampal CA3/4 fields at 1 h after lesioning. In injured animals with spreading depressions however, a strong elevation was seen in layers II-IV and VI of the injury-remote ipsilateral cerebral cortex, which persisted over as long as 6 h. Messenger RNA levels for c-fos, junB and MKP-1 were closely related to the time interval between the last depolarization and the end of experiment. Levels were highest shortly after transient direct current shifts, and decreased thereafter mono-exponentially with half-lives of 48, 75 and 58 min for c-fos, junB and MKP-1 messenger RNAs, respectively. In 6 h animals with spreading depressions, hsp72 messenger RNA was slightly elevated in layer II of the injury-remote cortex, but heat shock protein 72 was not increased. The present results demonstrate that spreading depression is the most prominent factor influencing the trauma-related gene response in the lesion-remote cortical tissue.

Recovery of the cerebral cortex after 10 min of cardiac arrest was studied in rat using noninvasive MRI techniques. The apparent diffusion coefficient (ADC) of brain water was imaged to document reversal of the metabolic impairment. Perfusion-weighted imaging and blood oxygen level dependent (BOLD) imaging were performed to assess functional recovery. To this purpose, rats were anesthetized with alpha-chloralose, and somatosensory cortex was activated by electrical stimulation of the contralateral forepaw. In sham-operated controls, cortical ADC was 862 +/- 10 microm2/s, and stimulation of forepaw led to a focal increase of signal intensity in somatosensory cortex by 71 +/- 22% in perfusion-weighted images and by 6 +/- 1% in BOLD images. One hour after successful resuscitation following 10 min of cardiac arrest, ADC did not differ from control but functional activation was completely suppressed. After 3 hours of reperfusion, functional activity began to reappear but the recovery of the BOLD signal progressed faster than that of the perfusion-weighted signal. The differences in the recovery of ADC, BOLD, and perfusion imaging are related to differences between metabolic and functional recovery on one hand and between blood flow and oxygen extraction on the other. The combination of these MRI methods thus provides detailed qualitative information about the progression of brain recovery after transient circulatory arrest.

Administration of inhibitors of neuronal nitric oxide synthase or deletion of the encoding gene in rodents provided evidence that neuronal nitric oxide synthase activity may contribute to neuronal cell death following global and focal cerebral ischemia. In the present study, we investigated by in situ hybridization the expression of an endogenous inhibitor of neuronal nitric oxide synthase activity, designated protein inhibitor of neuronal nitric oxide synthase and homologous to cytoplasmic dynein light chain, in the post-ischemic rat brain. Following global ischemia induced by cardiac arrest, messenger RNA expression of protein inhibitor of neuronal nitric oxide synthase was rapidly induced in pyramidal neurons of the hippocampal CA3 region and granule cell of the dentate gyrus which are resistant to ischemic damage. In vulnerable CA1 pyramidal neurons however, protein inhibitor of neuronal nitric oxide synthase expression remained at basal level after global ischemia and was associated with an increase in nicotinamide adenine dinucleotide phosphate-diaphorase activity and subsequent DNA fragmentation indicating ischemia-mediated neuronal cell death. Following focal cerebral ischemia induced by permanent occlusion of the middle cerebral artery, transcripts of protein inhibitor of neuronal nitric oxide synthase progressively accumulated in cortical neurons bordering the infarct area. After transient middle cerebral artery occlusion however, messenger RNA levels of protein inhibitor of neuronal nitric oxide synthase increased in the reperfused neocortex. Our findings indicate that cerebral ischemia leads to an increase in neuronal expression of protein inhibitor of neuronal nitric oxide synthase in brain regions where sustained or “uncoupled” nitric oxide synthase activity may be detrimental to neurons. Lack of post-ischemic induction of protein inhibitor of neuronal nitric oxide synthase in CA1 pyramidal neurons may result in high nitric oxide synthase activity after global ischemia and could contribute to delayed neuronal cell death.

We investigated the effects of global system for mobile communication (GSM) microwave exposure on the permeability of the blood-brain barrier using a calibrated microwave exposure system in the 900 MHz band. Rats were restrained in a carousel of circularly arranged plastic tubes and sham-exposed or microwave irradiated for a duration of 4 h at specific brain absorption rates (SAR) ranging from 0.3 to 7.5 W/kg. The extravasation of proteins was assessed either at the end of exposure or 7 days later in three to five coronal brain slices by immunohistochemical staining of serum albumin. As a positive control two rats were subjected to cold injury. In the brains of freely moving control rats (n = 20) only one spot of extravasated serum albumin could be detected in one animal. In the sham-exposed control group (n = 20) three animals exhibited a total of 4 extravasations. In animals irradiated for 4 h at SAR of 0.3, 1.5 and 7.5 W/kg (n = 20 in each group) five out of the ten animals of each group killed at the end of the exposure showed 7, 6 and 14 extravasations, respectively. In the ten animals of each group killed 7 days after exposure, the total number of extravasations was 2, 0 and 1, respectively. The increase in serum albumin extravasations after microwave exposure reached significance only in the group exposed to the highest SAR of 7.5 W/kg but not at the lower intensities. Histological injury was not observed in any of the examined brains. Compared to other pathological conditions with increased blood-brain barrier permeability such as cold injury, the here observed serum albumin extravasations are very modest and, moreover, reversible. Microwave exposure in the frequency and intensity range of mobile telephony is unlikely to produce pathologically significant changes of the blood-brain barrier permeability.

After a period of global cerebral ischemia, CO2 reactivity and the hemodynamic–metabolic activation to functional stimulation are transiently suppressed. This raises the question of whether the impaired functional coupling reflects disturbances of functional integrity of the brain or an impaired cerebrovascular reactivity. We, therefore, compared the recovery of CO2 reactivity with that of somatosensory evoked potentials, functional flow activation and neurologic deficits in a rodent model of cardiac arrest-induced cerebral ischemia, followed by up to 7 days of reperfusion. Cardiac arrest of 10 minutes' duration was produced in 24 animals by electrical fibrillation of the heart. Five animals were sham-operated controls. Resuscitation was performed by external cardiac massage, using standard resuscitation procedures. Functional activation was carried out under chloralose anesthesia by electrical stimulation of forepaws. CO2 reactivity was tested by ventilation of animals with 6% CO2. During functional and hypercapnic stimulation CBF was measured in the somatosensory cortex using laser–Doppler flowmetry, and at the end of the experiment by 14C-iodoantipyrine autoradiography. Neurologic deficits were scored by evaluating consciousness and various sensory and motor functions. In control animals 6% CO2 increased CBF measured by laser–Doppler flowmetry by 28.8% ± 8.7%. Forepaw stimulation generated somatosensory evoked potentials with an amplitude of 750 ± 217 μV and increased CBF measured by laser–Doppler flowmetry by 86.0% ± 18.1%. After return of spontaneous circulation, CO2 reactivity was transiently reduced to about 30% of control at 1 hour of reperfusion ( P < 0.05) but returned to near control at 5 hours. Somatosensory evoked potential amplitudes were reduced to 15% of control at 45 minutes of reperfusion and returned to only 50% to 60% at 3 and 7 days after return of spontaneous circulation ( P < 0.05). Functional activation of blood flow was completely suppressed during the first hour after return of spontaneous circulation but also recovered to 50% to 60% of control at 3 days after return of spontaneous circulation ( P < 0.05). Linear regression analysis revealed a significant correlation between recovery of functional activation of blood flow and both recovery of the amplitude of somatosensory evoked potentials ( P = 0.03) and the neurologic deficit score ( P = 0.02), but not between neurologic deficit score and recovery of CO2 reactivity or somatosensory evoked potential amplitudes. These data demonstrate that the suppression of functional activation of blood flow after 10 minutes cardiac arrest is not related to impairment of coupling mechanisms but reflects ongoing disturbances of the functional integrity of the brain. Assessment of functional flow coupling is a reliable way to study postischemic recovery of the brain.

The effect of trophic factors on neuronal survival after 30 min oxygen and glucose deprivation (in vitro ischemia) was studied in primary hippocampal and cortical neuronal cultures of rat. In vitro ischemia was produced at 37°C by placing cultures in glucose-free medium, the oxygen content of which was removed by gassing with pure argon. After in vitro ischemia neurons were allowed to recover either in serum-free minimal essential medium (MEM) or in MEM containing 5% native horse serum, 100 ng/ml basic fibroblast growth factor (bFGF) or 10 ng/ml transforming growth factor-β1 (TGF-β1), respectively. Cultures that recovered in serum-free medium suffered a progressive type of neuronal injury: survival of either cortical or hippocampal neurons declined from about 60% after 1 h to 50% after 3 h, 40% after 6 h and less than 20% after 24 h. Addition of serum proteins to the incubation medium did not influence early survival (up to 3-6 h) but significantly improved survival after 24 h (more than 40% in both hippocampal and cortical cultures). Addition of TGF-β1 and bFGF had only minor effects. These data show that serum reduces delayed ischemic cell death by a mechanism which is different from that of TGF-β1 or bFGF protection.

Intrastriatal injection of the excitotoxin N-methyl-dsc-aspartate (NMDA) in neonatal rat brain resulted in an acute ipsilateral decrease of the apparent diffusion coefficient (ADC) of brain tissue water, as measured with diffusion-weighted MRI. The early diffusion changes were accompanied by only mild changes in the overall metabolic status as measured by in vivo1H MRS and 31P MRS and metabolic imaging of brain sections. Minimal decreases in the high-energy phosphate levels and a small hemispheric acidosis were observed in the first 6¿h after NMDA administration. In addition, there was very modest lactate accumulation. Twenty-four hours after the induction of the excitotoxic injury the tissue energy status was still only moderately affected, whereas an overall decrease of 1H MRS-detected brain metabolites was found. Treatment with the non-competitive NMDA-antagonist MK-801 given within 90 min after NMDA injection rapidly reversed the NMDA-induced changes in the entire ipsilateral hemisphere. The effect of the competitive NMDA-antagonist D-CPPene was restricted to the cortical areas and was accomplished on a slower time scale. Our results indicate that; (i) early excitotoxicity in the neonatal rat brain does not lead to profound changes in the metabolic status; and (ii) brain tissue water ADC changes are not necessarily associated with a metabolic energy failure.

The β-amyloid precursor protein (APP) bears characteristics of an acute-phase protein and therefore is likely to be involved in the glial response to brain injury. In the brain, APP is rapidly synthesized by activated glial cells in response to comparatively mild neuronal lesions, e.g., a remote peripheral nerve injury. Perfusion deficits in the brain result largely in neuronal necrosis and are a common condition in elderly patients. This neuronal necrosis is accompanied by a pronounced reaction of astrocytes and microglia, which can also be observed in animal models. We have therefore studied in the rat, immunocytochemically, the induction of APP after 30 min of global ischemia caused by four-vessel occlusion. The postishemic brain injuries were examined at survival times from 12 h to 7 days. From day 3 onward, APP immunoreactivity was strongly induced in the CA1and CA4regions of the rat dorsal hippocampus as well as in the dorsolateral striatum. In these areas, the majority of APP-immunoreactive cells were reactive glial fibrillary acidic protein (GFAP)-positive astrocytes, as shown by double-immunofluorescence labeling for GFAP and APP. Additionally, small ramified cells, most likely activated microglia, expressed APP immunoreactivity. In contrast, in the parietal cortex, APP immunoreactivity occurred focally in clusters of activated microglia rather than in astrocytes, as demonstrated by double-immunofluorescence labeling for APP and the microglia-binding lectin Griffonia simplicifolia isolectin B4. In conclusion, following global ischemia, APP is induced in reactive glial cells with spatial differences in the distribution pattern of APP induction in astrocytes and microglia.

Glutamate neurotoxicity was studied in primary neuronal cultures prepared from rat cerebral cortex and hippocampal CA1 sector. Neurons were cultivated with 5% native horse serum and then exposed to 0.1 or 1.0 mM glutamate for 5 min. Subsequently, neurons were allowed to recover for 24 hours either in the presence or in the absence of 5% native horse serum. In the absence of serum, neurons showed morphological signs of degeneration and exhibited marked loss of vitality as tested by vital staining and release of lactate dehydrogenase (LDH). In contrast, when neurons were cultivated in the presence of serum, no degenerative changes were seen and the neurons survived. Heat inactivated serum did not prevent neuronal death but addition of basic fibroblast growth factor (bFGF) or transforming growth factor-beta 1 (TGF-beta 1) had the same protective effect as native serum. Measurements of intracellular calcium activity ([Ca2+]i) with the indicator dye fura-2 revealed a sharp increase during glutamate exposure. In the absence of serum, [Ca2+]i returned to near control within 5 min but it secondarily increased after 1 hour to almost the same level as during glutamate exposure. This delayed increase was more pronounced in CA1 than in cortical neurons, it correlated linearly with the initial rise during glutamate exposure, and it was greatly reduced in the presence of serum. These observations suggest that glutamate neurotoxicity in vitro is a function of the delayed and not of the primary rise of intracellular calcium activity, and that trophic factors prevent neurotoxicity by attenuating this delayed response.

The temporospatial expression pattern of four immediate early genes (IEGs) (c- fos, c- jun, junB, NGFI-B) following 30 min of global ischemia was investigated in rat brains by in situ hybridization and immunohistochemistry (c- fos). All examined IEG mRNAs, as well as Fos-like immunoreactivity, increased transiently in vulnerable and resistant brain regions following ischemia, but the induction profiles were distinct. Ischemia caused a post-ischemic early-onset, transient c- fos induction in widespread regions, as well as a late-onset induction restricted to vulnerable regions. Late-onset c- fos induction was observed in the CA1 region and the ventral thalamus but not in the striatum or neocortex, where neurons degenerate at a quicker pace. After recirculation, c- jun mRNA appeared to be initially coinduced with c- fos mRNA, but c- jun mRNA levels remained elevated or increased in various regions, including all vulnerable regions, when c- fos mRNA had already declined to near basal levels. Compared to c- fos and c- jun, junB induction was less pronounced and confined largely to the dentate gyrus. NGFI-B mRNA increased moderately and only in brain regions exhibiting the most dramatic c- fos increases and with similar kinetics. The differential activation of the investigated IEGs suggests that rather complex long-term adaptive processes may be initiated at the genomic level after global ischemia. The present findings provide further evidence that the activation of IEGs forms part of the brain's metabolic response to ischemia, but no simple correlation appears to exist between the induction of the investigated IEGs and the phenomenon of selective vulnerability.

In the periphery of ischemic brain lesions, transient spreading depression-like direct current (DC) deflections occur that may be of pathophysiological importance for determining the volume of the ischemic infarct. The effect of these deflections on cerebral blood flow, tissue oxygen tension, and electrophysiology was studied in rats submitted to intraluminal thread occlusion of the middle cerebral artery (MCA) and compared with the changes following potassium chloride (KCl)-induced spreading depression of intact animals. Immediately after MCA occlusion, cortical laser–Doppler flow (LDF) in the periphery of the MCA territory sharply decreased to 35 ± 14% of control (mean ± SD; p < 0.05), tissue Po2 declined from 28 ± 4 to 21 ± 3 mm Hg (p < 0.05), and EEG power fell to ∼80% of control. During 7-h occlusion, 3–11 DC deflections with a mean duration of 5.2 ± 4.8 min occurred at irregular intervals, and EEG power gradually declined to 66 ± 16% of control (p < 0.05). During the passage of DC deflections, LDF did not change, but Po2 further declined to 19 ± 4 mm Hg (p < 0.05). KCl-induced depolarizations of intact rats were significantly shorter (1.4 ± 0.5 min; p < 0.05) and were accompanied by a 43% increase in LDF (p < 0.05) and a slight but significant increase in tissue Po2 from 22 ± 4 to 25 ± 4 mm Hg (p < 0.05). The comparison of periinfarct and KCl-induced depolarizations demonstrates that oxygen requirements are not coupled to an appropriate flow response in the periinfarct zone with severely reduced blood flow. The resulting episodes of relative hypoxia could explain the previously documented relationship between the number of depolarizations and infarct volume.

The effect of the glutamate antagonist MK-801 on the ischemic threshold of energy metabolism and protein synthesis (CPS) was studied in rats submitted to 3 h occlusion of the left middle cerebral artery (MCA). Local blood flow and CPS were measured by double tracer autoradiography, and local ATP content by bioluminescence imaging. In untreated animals breakdown of energy metabolism occurred at flow values below 15 +/- 1 and CPS inhibition below 51 +/- 15 ml/100 g/min (means +/- S.D.). MK-801 treatment (3 mg/kg immediately after MCA occlusion) did not change the ischemic flow threshold of energy failure (16 +/- 3 ml/100 g/min) but lead to a highly significant decline of the perfusion threshold for the inhibition of CPS to 19 +/- 4 ml/100 g/min (P0.01). Our data demonstrate that MK-801 dramatically reduces the threshold for the suppression of protein synthesis which could explain previously reported therapeutical effects on the reduction of brain infarct size.

The relationship between blood flow and metabolism was studied in halothane-anaesthetized, normothermic rats submitted to 30 min global ischemia by four-vessel occlusion. Phosphocreatine (PCr), ATP, intracellular pH and intracellular magnesium (pMg) were measured by "P NMR spectroscopy, and blood flow by laser Doppler flowmetry. Prior to ischemia the PCr/ATP ratio of fully relaxed spectra was 2.4 k 0.3, intracellular pH was 7.26 +_ 0.15 and pMg was 3.26 f 0.13. Vascular occlusion led to complete cessation of blood flow in four out of eight rats, and to incomplete ischaemia (< 10% of control) in the other four animals. During vascular occlusion EEG Battened and energy metabolism broke down in all but one animal with a residual blood flow of 8% of control. pH declined to 6.70 f 0.08. The speed of electrophysiological and metabolic recovery after 30 min ischemia varied considerably from animal to animal. Variability depended mainly on the recirculation delay (i.e., the interval from vascular release to normalization of blood flow) but was independent of residual blood flow during ischemia, pre-ischemic glucose, ischemic or post-ischemic acidosis, or the degree of post-ischemic hypoperfusion. After 3 h recirculation PCr and intracellular pH returned to normal but pMg was slightly increased, and ATP was reduced by up to 50% in all animals except the rat with incomplete breakdown of energy metabolism during ischemia. The dissociation between PCr and ATP is attributed to a loss of total adenylate, the severity of which depends on the quality of post-ischemic recirculation. The data refute the hypothesis that the quality of post-ischemic metabolic recovery depends mainly on the severity of tissue acidosis but stress the importance of post-ischemic haemodynamic factors for the speed and quality of brain resuscitation.

The rate of leucine incorporation into brain proteins was studied in rats with experimental brain tumors produced by intracerebral transplantation of the glioma clone F98. Incorporation was measured with [14C]leucine using a controlled infusion technique for maintaining constant specific activity of [14C]leucine in plasma, followed by quantitative autoradiography and biochemical tissue analysis. After 45 min the specific activity of free [14C]leucine in plasma was 2.5-3 times higher than in brain and brain tumor, indicating that the precursor pool for protein synthesis was fueled both by exogenous (plasma-derived) and endogenous (proteolysis-derived) amino acids. Endogenous recycling of amino acids amounted to 73% of total free leucine pool in brain tumors and to 60-70% in normal brain. Taking endogenous amino acid recycling into account, leucine incorporation was 78.7 +/- 16.0 nmol/g of tissue/min in brain tumor, and 17.2 +/- 4.2 and 9.7 +/- 3.3 nmol/g/min in normal frontal cortex and striatum, respectively. Leucine incorporation within tumor tissue was markedly heterogeneous, depending on the local pattern of tumor proliferation and necrosis. Our results demonstrate that quantitative measurement of leucine incorporation into brain proteins requires estimation of recycling of amino acids derived from proteolysis and, in consequence, biochemical determination of the free amino acid precursor pool in tissue samples. With the present approach such measurements are possible and provide the quantitative basis for the evaluation of therapeutic interventions.

The effect of various anesthetics on the functional-metabolic coupling of cerebral cortex was studied in rats submitted to unilateral somatosensory stimulation. The regional cerebral metabolic rate of glucose (CMRglc) was measured autoradiographically using the 2-deoxyglucose method, and somatosensory activation was carried out by electrical stimulation of the left forepaw. In animals treated with 70% nitrous oxide, 0.5% halothane/70% nitrous oxide or 40 mg/kg pentobarbital, CMRglc of somatosensory cortex did not change despite generation of primary evoked cortical potentials. Anesthesia with 80 mg/kg alpha-chloralose, in contrast, led to a focal increase of CMRglc in the primary somatosensory cortex from 52.1 +/- 18.3 to 73.1 +/- 18.9 mumol/100 g/min (means +/- s.d.). Metabolic activation was strictly confined to the forelimb (FL) area of somatosensory cortex, and it exhibited a laminar pattern with maximal activation in layers I, II and IV. The preservation of functional-metabolic coupling under a surgical dose of chloralose renders this anesthetic particularly suited for the investigation of coupling processes under conditions where the experimental requirements preclude the use of unanaesthetized animals.

The ischemic threshold of protein synthesis and energy state was determined 1, 6, and 12 h after middle cerebral artery (MCA) occlusion in rats. Local blood flow and amino acid incorporation were measured by double tracer autoradiography, and local ATP content by substrate-induced bioluminescence. The various images were evaluated at the striatal level in cerebral cortex by scanning with a microdensitometer with 75 μm resolution. Each 75 × 75 μm digitized image pixel was then converted into the appropriate units of either protein synthesis, ATP content, or blood flow. The ischemic threshold was defined as the flow rate at which 50% of pixels exhibited complete metabolic suppression. One hour after MCA occlusion, the threshold of protein synthesis was 55.3 ± 12.0 ml 100 g−1 min−1 and that of energy failure was 18.5 ± 9.8 ml 100 g−1 min−1. After 6 and 12 h of MCA occlusion, the threshold of protein synthesis did not change (52.0 ± 9.6 and 56.0 ± 6.5 ml 100 g−1 min−1, respectively) but the threshold of energy failure increased significantly at 12 h following MCA occlusion to 31.9 ± 9.7 ml 100 g−1 min−1 ( p < 0.05 compared to 1 h ATP threshold value; all values are mean ± SD). In focal cerebral ischemia, therefore, the threshold of energy failure gradually approached that of protein synthesis. Our results suggest that with increasing duration of ischemia, survival of brain tissue is determined by the high threshold of persisting inhibition of protein synthesis and not by the much lower one of acute energy failure. If the ischemic penumbra is considered to comprise the region in which cerebral protein synthesis is suppressed and energy state is preserved, it follows that the size of the penumbra decreases with the duration of ischemia.

The effect of increasing static magnetic field strength up to 4.7 Tesla on the electrical function of the cat brain was studied by EEG frequency analysis and recording of somatosensory evoked potentials. While the latencies of the peaks P6 and P10 of the somatosensory evoked potentials were stable during the time course of the experiment, EEG intensity, EEG frequency index and the P10/N15 amplitude showed substantial fluctuations

A quantitative method for determination of endogenous serum proteins has been established and tested in an experimental model of peritumoural brain oedema in cats. Rocket and crossed immunoelectrophoresis were applied for determination of total serum proteins, albumin, IgG and haemoglobin in blood and brain homogenates. Modifications such as the use of non-ionic detergents and of antisera with different specificity were established for each antigen under investigation. The content of total serum proteins, albumin and IgG was substantially higher in tumour and peritumoural brain tissue than in the non-oedematous brain. The measurement of haemoglobin allowed the calculation of blood volume and, in consequence, the differentiation between intra- and extravascular serum proteins. The results are in line with earlier measurements obtained by different analytical methods and demonstrate that the present technique provides a reliable approach for the quantitative assessment of serum protein extravasation.

Coupling between local perfusion and metabolism was examined in Mongolian gerbils during the development of delayed neuronal death using a combination of double-tracer autoradiography and imaging of local energy state. Animals were anesthetized with 1.5% halothane and forebrain ischemia was produced by occluding both common carotid arteries. After 5 min of ischemia, brains were recirculated for 6 h and 1, 2, or 4 days. At the end of the experiment, regional cerebral blood flow (CBF) and glucose utilization (CMRglc) were determined in identical brain sections with [131I]iodoantipyrine and [14C]deoxyglucose, respectively. Adjacent sections were taken for imaging of ATP and glucose using substratespecific bioluminescence reactions. In the CA1 subfield of control animals, CBF and CMRglc amounted to 81 ± 8 ml 100g−1 min−1 and 69 ± 2 μmol 100 g−1 min-1, respectively, and the calculated CBF/CMRglc ratio was 1.18 ± 0.12 ml/μmol (mean ± SD). After ischemia, the CBF/CMRglc ratio increased to 1.31 ± 0.14, 1.43 ± 0.16, 1.45 ± 0.16, and 1.56 ± 0.18 ml/μmol following 6 h and 1, 2, or 4 days recirculation, respectively. Glucose levels did not change during the 6 h to 4 day recirculation period in the hippocampal CA1 subfield. In the same region, ATP levels were unchanged during 6 h to 2 day postischemic recovery but reduced to about 70% after 4 days of recirculation. The results indicate that a mismatch of the flow-metabolism couple following transient ischemia does not appear to contribute to the postischemic maturation of delayed neuronal death in selectively vulnerable brain regions.

The effect of manganese(III)tetraphenylporphine sulfonate (MnTPPS) on the relaxation enhancement of NMR images (MRI) was studied in experimental brain tumors in rats. Brains were inoculated with the glioma cell line F98 12 to 19 days before the NMR experiment, and the effect of MnTPPS (0.25 mmol/kg body weight) was investigated 2 and 4 days after intraperitoneal injection. After MnTPPS addition tumors could be clearly distinguished by the brightness from the surrounding brain whereas they were barely visible without contrast enhancement. At SE time of 25 msec and TR time of 3500 msec the ratio of magnetization values of tumor versus normal grey matter increased from 0.98 ± 0.08 to 1.24 ± 0.09 (means ± SD). When TR was shortened to 1100 msec contrast enhancement further increased to 1.77 ± 0.25. These results demonstrate for the first time that MnTPPS is an efficient agent for contrast enhancement of brain tumors.

The dorsal hippocampus of cat was investigated by light microscopy and immunohistochemistry following 1 h global cerebral ischemia and various recirculation times from 1 day to 1 year. Complete ischemia was produced by combining hypotension with intrathoracic occlusion of major arteries. Post-ischemic resuscitation was carried out using an intensive care regimen with continuous neurophysiological monitoring. Brains of controls (n = 4) and post-ischemic animals (n = 12) were fixed in formaldehyde and prepared for histology and immunohistochemistry of glial fibrillary acidic protein (GFAP). In all post-ischemic animals the hilus and the regio superior of dorsal hippocampus which encompasses the CA1 subfield were severely damaged. Neurons in these regions exhibited the typical sequela of neuronal death. GFAP staining revealed vivid astroglial proliferation in stratum lacunosum-moleculare and stratum oriens. Changes in the regio inferior of dorsal hippocampus, i.e., CA3 subfield, and in dentate gyrus granular layer, were variable. Although most animals exhibited moderate to severe neuronal and glial alterations, groups of surviving cells were observed in the stratum oriens and in the granular layer of dentate gyrus. In one animal the majority of CA3 pyramidal cells and granule cells was preserved. These findings demonstrate that after 1 h of complete cerebral ischemia dorsal hippocampus exhibits two different types of injury: a consistent pattern of selective vulnerability in the hilus and the regio superior, and a variable pattern of non-selective injury in the regio inferior and dentate gyrus. The two patterns can be best explained by intrinsic (pathoclitic) and extrinsic (hemodynamic/edema) factors, respectively and are likely to represent basically different mechanisms of ischemic injury.

Transient forebrain ischemia of 30 min duration was produced in anaesthetized rats by four-vessel occlusion. After survival periods of 3 h to three days brains were perfusion-fixed and sections through the mid-dorsal hippocampus were processed for conventional staining and immunohistochemical analysis. Neuronal damage in the hilus was manifested 3-8 h after ischemia; neurons in the CA1 and CA2 sector suffered delayed neuronal death after 48-72 h whereas the dentate gyrus and the CA3 sector were normal. Vasogenic edema formation was visualized using antibodies against rat serum-proteins, serum albumin and immunoglobulins. By 3 h after ischemia, only faint and diffuse serum-staining was detected. At 8 h survival, weak astrocytic-staining was present. After 24-72 h CA1-CA2 exhibited massive serum extravasation. The molecular layer of the dentate gyrus showed edema formation in the absence of granule cell damage. The glial reaction was studied using antibodies against glial fibrillary acidic protein, vimentin and S-100 protein. Glial fibrillary acidic protein and S-100 protein-staining increased in areas with either edema or neuronal damage. In contrast, changes in vimentin were only detected in areas with neuronal necrosis. The observations demonstrate that following 30 min of ischemia neuronal damage is accompanied by changes in blood-brain barrier function and reactive glial alterations. The dissociation between neuronal necrosis and astroglial hypertrophy and hyperplasia reflects differences in cellular responsiveness which constitute inherent features of postischemic hippocampal injury.

Brain damage induced by focal interruption of blood flow can be differentiated in two pathophysiologically different categories: a hemodynamic type of injury, resulting in primary necrotic brain damage, and a molecular type of injury which leads to delayed or secondary brain injury [15]. Primary necrotic brain injury occurs when blood flow declines - and remains - below the threshold of energy failure. In anaesthetized laboratory animals, this threshold gradually increases from about 15% of control shortly after the onset of ischemia to about 30% after several hours of vascular occlusion [29].

Brain damage induced by focal interruption of blood flow can be differentiated in two pathophysiologically different categories: a hemodynamic type of injury, resulting in primary necrotic brain damage, and a molecular type of injury which leads to delayed or secondary brain injury [15]. Primary necrotic brain injury occurs when blood flow declines — and remains — below the threshold of energy failure. In anaesthetized laboratory animals, this threshold gradually increases from about 15% of control shortly after the onset of ischemia to about 30% after several hours of vascular occlusion [35].

The therapeutical potential of transplantation of undifferentiated and predifferentiated murine embryonic stem cells for the regeneration of the injured brain was investigated in two rodent stroke models. Undifferentiated embryonic stem cells xenotransplanted into the rat brain at the hemisphere opposite to the ischemic injury migrated along the corpus callosum towards the damaged tissue and differentiated into neurons in the border zone of the lesion. In the homologous mouse brain, the same murine embryonic stem cells did not migrate, but produced highly malignant teratocarcinomas at the site of implantation, independent of whether they were predifferentiated in vitro to neural progenitor cells. The authors demonstrated a hitherto unrecognized inverse outcome after xenotransplantation and homologous transplantation of embryonic stem cells, which raises concerns about safety provisions when the therapeutical potential of human embryonic stem cells is tested in preclinical animal models.

The evolution of brain injury was examined in mice subjected to focal cerebral ischemia as induced by 30 min of intraluminar thread occlusion of the middle cerebral artery, followed by 3 h to 3 days of reperfusion. Metabolic dysfunctions were studied by 3H-leucine autoradiography for the measurement of cerebral protein synthesis and by regional ATP bioluminescent imaging. Metabolic changes were compared with responses of the genes c-fos, c-jun, heat-shock protein gene (hsp)72, p53-activated gene (pag)608 and caspase-3, which were investigated by in situ hybridization histochemistry and immunocytochemistry, and correlated with the degree of DNA fragmentation, as assessed by the terminal TdT-mediated dUTP-biotin nick end labeling method. Intraluminar thread occlusion led to a reproducible reduction of cerebral laser Doppler flow to 20-30% of control. Thread withdrawal was followed by a short-lasting post-ischemic hyperperfusion to approximately 120%. In non-ischemic control animals, fractional protein synthesis values of 0.81+/-0.26 and 0.94+/-0.23 were obtained. Thread occlusion resulted in a suppression of protein synthesis throughout the territory of the middle cerebral artery after 3 h of reperfusion (0.04+/-0.08 in caudate-putamen and 0.14+/-0.19 in somatosensory cortex, P

The effects of post-ischemic recirculation on regional cerebral metabolism and DNA fragmentation was examined in mice subjected to 30 min, 1 h or 2 h transient middle cerebral artery occlusion (MCAO) followed by 1 h to 3 days recirculation. At the end of ischemia, the regional extent of metabolic disturbances was roughly the same, irrespective of the length of ischemia (ATP depletion: 452–54%; cerebral protein synthesis (CPS) suppression: 59–65% of ipsilateral hemisphere). During recirculation, ATP initially recovered but then secondarily declined, the severity of deterioration depending on the duration of MCAO and the recovery of CPS. Areas of residual CPS suppression and secondary ATP depletion were 11±14% and 3±5% after 30 min MCAO, 37±7% and 35±9% after lh MCAO, and 60±8% and 61±10% after 2h MCAO, respectively. Single- and double-strand DNA breaks appeared after 3 h recirculation in those areas in which CPS did not return, covering 19±17% and 19±19% of contralateral hemisphere after 30 min MCAO, 27±9% and 32±9% after 60 min of MCAO, and 58±7% and 59±19% after 2 h MCAO. These data suggest that secondary energy failure after transient MCAO is heralded by persisting inhibition of CPS and accompanied by single- and double-strand DNA fragmentations.

The effects of intracarotid thrombolysis with recombinant tissue-plasminogen activator (rt-PA) on cerebral laser Doppler flow (LDF) and the degree of ischemic injury, as revealed by triphenyltetrazolium chloride (TTC) staining, were studied 24 h following cerebral thromboembolism in mice. Thromboembolization with fibrin-rich clot material (0.28-microl clot volume) led to an LDF decline to about 20-30% of baseline in untreated mice, which resulted in reproducible infarcts of the middle cerebral artery (MCA) territory (122.8 +/- 29.4 mm(3)). Administration of rt-PA (10 mg/kg) 15 min after clot injection induced a progressive LDF restoration to approximately 115% of control values after 2 h, and brought about a significant reduction of the infarct volume (62.3 +/- 42.4 mm(3)). Our results indicate that ischemic injury may be significantly attenuated by intracarotid thrombolysis. However, injury is not completely reversed, even if reperfusion is initiated as early as 15 min after embolization.

Rats submitted to focal cerebral ischemia by middle cerebral artery clot embolism were treated with recombinant tissue plasminogen activator (rt-PA) at increasing delays (1.5, 3 and 4.5 h) after the onset of ischemia. Treatment efficacy was evaluated by NMR imaging of the apparent diffusion coefficient of water (ADC). In untreated animals the size of the ADC-detectable lesion gradually increased after clot embolism, expanding over 8 h to 174 +/- 17% of the volume visible at 30 min. Thrombolysis initiated 1.5 h after embolism did not reverse the ischemic lesion but reduced its growth to 113 +/- 19% (p < 0.05). Lesion size increased to 135 +/- 14% after 3 h (NS) and to 214 +/- 35% after 4.5 h delay (NS). Thrombolysis with rt-PA attenuates infarct expansion but does not reverse ischemic injury.

An essential role for caspases in programmed neuronal cell death has been demonstrated in various in vitro studies, and synthetic caspase inhibitors have recently been shown to prevent neuronal cell loss in animal models of focal cerebral ischemia and traumatic brain injury, respectively. The therapeutic utility of caspase inhibitors, however, will depend on preservation of both structural and functional integrity of neurons under stressful conditions. The present study demonstrates that expression and proteolytic activity of caspase-3 is up-regulated in the rat hippocampus after transient forebrain ischemia. Continuous i.c.v. infusion of the caspase inhibitor N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone significantly attenuated caspase-3-like enzymatic activity, and blocked delayed cell loss of hippocampal CA1 neurons after ischemia. Administration of N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethyl ketone, however, did not prevent impairment of induction of long-term potentiation in post-ischemic CA1 cells, suggesting that caspase inhibition alone does not preserve neuronal functional plasticity.

Brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF) are distributed widely within the central nervous system and convey neuroprotection against apoptosis and various metabolic and excitotoxic insults. We investigated whether these factors could limit infarct size in a model of permanent occlusion of the middle cerebral artery (MCA) in rat. BDNF and CNTF were infused into the territory of the occluded MCA using an osmotic minipump. The infusion was started shortly after vascular occlusion and continued for 24 h. Brains were removed at this time for determination of infarct volume and the presence and distribution of DNA-fragmented cells, using in situ end labeling with terminal deoxynucleotidyl transferase (TUNEL staining). BDNF produced a 33% reduction of total infarct volume, compared with vehicle-treated animals (P

The high energy requirements compared to the low energy reserves render the brain particularly vulnerable to hypoxic conditions. To protect the brain against hypoxia, powerful cerebrovascular regulatory systems assure an increase of blood flow to compensate for the reduced arterial oxygen content. This system is so efficient that during respiratory hypoxia brain metabolism is little disturbed as long as cardiac function does not fail. Only with declining blood pressure cerebral blood flow also declines, and brain energy metabolism rapidly collapses.

The effects of a cortex lesion on alterations in cortical direct-current (DC) potential, cerebral metabolism and gene expression were examined in rats at 1–6 h after transcranial cold injury. In 14 of 21 injured rats, spreading depression (SD)-like depolarizations were recorded, which were accompanied by a transient decrease in electroencephalogram activity and a parallel increase in perfusion. Metabolic disturbances did not differ between injured animals with and without SD. The lesion surrounding was characterized by increased glucose and lactate contents without major disturbances of protein synthesis or energy state. A transient peri-focal decrease in tissue pH by 0.4 units was noticed after 1 h, followed by tissue alkalosis 3 h post-injury. In injured animals without SD, a short-lasting expression of immediate-early gene (IEG) mRNAs was found in piriform cortex, in the dentate gyrus and hippocampal CA3/CA4 subfields at 1 h after lesioning. In injured animals with SDs, a strong elevation of IEGs was seen additionally in layers II-IV and VI of the injury-remote ipsilateral cerebral cortex, which persisted for as long as 6 h. The mRNA levels for c-fos, junB and mitogen-activated protein kinase phosphatase (MKP)-1 were closely related to the time interval between the last DC deflection and the termination of the experiment, yielding a post-depolarization decline with half-lives of 48, 75, and 58 min for c-fos, junB and MKP-1, respectively. The results of the present study demonstrate that SD is a prominent factor influencing trauma-related gene responses in the lesion-remote cerebral cortex. In contrast to focal cerebral ischemia, however, SDs do not aggravate the metabolic dysfunction in the area surrounding the lesion.

Following transient global cerebral ischemia, there is a progressive increase in nitric oxide (NO) synthase activity in hippocampal CA1 neurons that may be enhanced by a lack of protein inhibitor of neuronal NO synthase (PIN). The concomitant accumulation of NO and other reactive oxygen species causes deoxyribonucleic acid (DNA) injury, as indicated by the futile attempt to activate the DNA repair enzyme, ref-1, and by the expression of DNA damage-inducible, cell death-promoting PAG608 in CA1 neurons 1 day after ischemia. Nuclear phospho-c-Jun(Ser-73) immunoreactivity becomes apparent in CA1 cells, suggesting that oxidative stress and DNA damage activate c-Jun N-terminal kinases. One day after ischemia, expression of caspase-3 is upregulated in CA1 neurons and caspase-3-like proteolytic activity increases in hippocampal extracts. Intracerebroventricular infusion of the caspase inhibitor, Z-DEVD-FMK, prevents CA1 cell loss, indicating that CA1 cells die by programmed cell death. Following transient focal ischemia, PIN transcripts and phospho-c-Jun rapidly accumulate in neurons of the reperfused cortex. Immunoreactivity for Bcl-2-associated death protein (Bad) becomes apparent in post-ischemic cortical neurons. Furthermore, the infarct area is significantly larger in bcl-2-deficient mice, strongly suggesting that Bcl-2 and related proteins influence neuronal cell death after focal ischemia.

The heterogeneity of c-fos and hsp72 mRNA expression during focal ischemia was studied in mice by combining in situ hybridization with metabolic imaging. Focal ischemia was produced by middle cerebral artery occlusion for 3 h. The infarct core and the penumbra were differentiated by regional ATP and cerebral protein synthesis (CPS) imaging. hsp72 mRNA expression was restricted to the ischemic penumbra, as defined by the dissociation between preserved ATP and suppressed CPS. c-fos mRNA was expressed not only in the penumbra but also in the peri-ischemic normal brain tissue in which both ATP and CPS were preserved. These data demonstrate a highly selective differential expression of immediate-early and stress-related genes in the peri-infarct surrounding which is explained by different mechanisms of gene induction.

The effect of the novel inhibitor of receptor-activated and calcium store-operated nonselective cation channels, (RS)-(3,4-dihydro-6,7-dimethoxyisoquinoline-1-gamma 1)-2-phenyl-N, N-di-[2(2,3,4-trimethoxyphenyl) ethyl]acetamide (LOE 908 MS), on focal cerebral ischemia was studied in halothane-anesthetized rats submitted to permanent suture occlusion of the right middle cerebral artery (MCA). The treated group (n = 7) received subcutaneous injections of 30 mg/kg LOE 908 MS (in 1 ml saline) 10 min after vascular occlusion and again after 3 h. The untreated group (n = 11) was injected subcutaneously with 1 ml saline at the same times. Evolution of infarct was monitored by electrophysiological recording of EEG and cortical steady potential and by diffusion-weighted magnetic resonance imaging during the initial 6 h of vascular occlusion. The hemodynamic, biochemical, and morphological changes were studied after 6 h by combining autoradiographic measurement of blood flow with histological stainings and pictorial measurements of ATP, glucose, and tissue pH. In the untreated animals, the ischemic lesion volume [defined as the region in which the apparent diffusion coefficient (ADC) of water declined to below 80% of control] steadily increased by approximately 50% during the initial 6 h of vascular occlusion relative to the first set of data 10 min postocclusion. In the treated animals, in contrast, the ADC lesion volume declined by approximately 20% during the same interval. Treatment also led to a significant reduction in the number of periinfarct depolarizations. After 6 h of vascular occlusion, blood flow was significantly higher in the treated animals, and the volume of ATP-depleted and morphologically injured tissue representing the infarct core was 60-70% smaller. The volume of severely acidic tissue, in contrast, did not differ, indicating that LOE 908 MS does not reduce the size of ischemic penumbra. These findings demonstrate that postocclusion treatment of permanent focal ischemia with LOE 908 MS delays the expansion of the infarct core into the penumbra for a duration of at least 6 h and therefore substantially prolongs the window of opportunity for the reversal of the ischemic impact in the peripheral parts of the evolving infarct.

The astroglial and microglial reaction to ischemic neuronal death was studied in hippocampus of rats submitted to 30-min, near-complete forebrain ischemia. The global metabolic response to ischemia was assessed by measuring energy metabolism and protein synthesis, and the cell-specific reactions by using a battery of histological, in situ hybridization and immunocytochemical techniques.