Biomedical subjects

F R Sharp

Publications and source records attributed to F R Sharp.

At least 73 records · Page 4Linked to original sources

PubMed1996

DNA fragmentation and HSP70 protein induction in hippocampus and cortex occurs in separate neurons following permanent middle cerebral artery occlusions.

DNA nick end-labeling (TUNEL) and heat shock protein (HSP)70 immunocytochemistry were performed on the same brain sections 1 (n = 6), 3 (n = 12), and 7 (n = 7) days following permanent middle cerebral artery (MCA) occlusions produced in adult rats using the endovascular carotid suture method. In the cortex at 1 and 3 days following MCA occlusions, HSP70 immunoreactive neurons were located outside areas of infarction and showed little evidence of DNA fragmentation. HSP70-stained cortical neurons were intermingled with TUNEL cells near the infarct, but extended for greater distances away from the infarct. DNA fragmentation occurred in CA1 hippocampal neurons in 39% of the animals at 1 and 3 days following ipsilateral MCA occlusion. Bilateral DNA fragmentation occurred in CA1 neurons in one subject. HSP70 protein was expressed in CA1 hippocampal neurons in nine of 18 (50%) animals at 1 and 3 days following MCA occlusions, including all animals that exhibited hippocampal DNA fragmentation. Three animals had bilateral expression of HSP70 in CA1 neurons. Cells that stained for either HSP70 protein or DNA fragmentation existed in close proximity to one another. Approximately 5-7% of HSP70-stained cells were TUNEL stained and 3% of TUNEL-positive cells also stained for HSP70. There was no HSP70 staining or DNA fragmentation in the brains of sham-operated controls (n = 4) or in the brains of animals 7 days following MCA occlusions. These data suggest that ischemic cells capable of translating HSP70 protein generally do not undergo DNA fragmentation. These data support the concept that most HSP70 protein-containing neurons in the cortical "penumbra" and hippocampus survive ischemic injury and are "reversibly injured." It is shown that CA1 hippocampal pyramidal neurons die or are reversibly injured in approximately 50% of animals following permanent MCA occlusions. Although the mechanism of this hippocampal injury is unknown, it could relate to transynaptic activation of N-methyl-D-aspartate (NMDA) receptors that mediate induction of early genes in hippocampus.

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PubMed1996

Eliprodil prevents expression of the 70 kDa heat shock protein in MK801-injured neurones.

The present study examined whether eliprodil (SL 82.0715), an N-methyl-D-aspartate (NMDA) receptor antagonist acting on the polyamine sites induced expression of the 70 kDa heat shock protein (HSP70) in the rat brain. Whereas the NMDA channel blocker MK801 consistently induced HSP70 in posterior cingulate and retrosplenial cortices, eliprodil had no such effects even at the highest dose (50 mg/kg, intraperitoneally), supporting the idea that injury to the cerebrocortical neurones by NMDA receptor antagonists is probably related to specific sites of the receptor. Furthermore, eliprodil, given immediately after injection of MK801, blocked the effects of MK801 on HSP70. The result is discussed in terms of high affinity of eliprodil for the sigma receptor.

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PubMed1996

MK-801 reduces uptake and stimulates efflux of excitatory amino acids via membrane depolarization.

MK-801 and related compounds reduce excitotoxic neuronal injury by blocking N-methyl-D-aspartate (NMDA) receptorgated ion channels. These agents also cause neuronal vacuolization and block glutamate-induced astrocyte swelling, effects that may be unrelated to actions at the NMDA receptor. In the present study, high concentrations of MK-801 (100-1,000 microM) caused uncompetitive inhibition of glutamate uptake in astrocyte and neuronal cultures and stimulated D-aspartate efflux from astrocytes. MK-801 (500 microM) reduced the maximal velocity for glutamate uptake in astrocytes from 31 to 17 nmol.mg protein-1.min-1, whereas competitive NMDA receptor antagonists did not affect glutamate uptake. MK-801 also inhibited uptake of gamma-aminobutyric acid (GABA). Because both GABA uptake and glutamate uptake are electrogenic, one mechanism by which MK-801 could inhibit uptake is by membrane depolarization. Whole cell patch-clamp recording confirmed that MK-801 in the range of 100-1,000 microM caused dose-dependent and reversible depolarization. These concentrations are far higher than necessary to block NMDA receptors, and the findings suggest that actions at sites other than NMDA receptors could contribute to the effects of high doses of MK-801 in some experimental and clinical settings.

Amino Acids↗

PubMed1996

Subarachnoid injections of lysed blood induce the hsp70 stress gene and produce DNA fragmentation in focal areas of the rat brain.

BACKGROUND AND PURPOSE: Most experimental studies of subarachnoid hemorrhage have demonstrated little histological evidence of injury. In the present study we examined both the expression of the hsp70 heat-shock gene, a molecular marker of reversible neuronal injury, and DNA fragmentation, a marker of irreversible cell injury and death. METHODS: Lysed blood, whole blood, oxyhemoglobin, bovine serum albumin, and saline were injected into the cisterna magna of adult rats. The induction of hsp70 mRNA and HSP70 heat-shock protein was assessed with the use of in situ hybridization and immunocytochemistry, respectively. Fragmentation of genomic DNA was studied by DNA nick end- labeling with the use of terminal deoxynucleotidyl transferase and biotinylated dATP. RESULTS: Expression of the hsp70 gene was not induced in the brains of rats injected with whole blood, oxyhemoglobin, bovine serum albumin, or saline. Lysed blood injections, however, induced hsp70 mRNA at 6 and 24 hours in the cerebellar hemispheres and in focal regions of the basal forebrain. HSP70 protein was induced by 24 hours and persisted for at least 4 days in the same regions. HSP70 protein was localized to patches of glial cells and occasional neurons in the forebrain. In the cerebellum HSP70 was localized to Bergmann glial cells, granule cells, molecular layer stellate cells, and occasional Purkinje cells. DNA nick end-labeling showed patches of labeled cells in the basal forebrain that occurred in the same regions that hsp70 mRNA was induced. CONCLUSIONS: The results demonstrate focal stress gene induction and DNA fragmentation after subarachnoid hemorrhage. It is hypothesized that the focal areas of hsp70 induction may reflect ischemic injury due to vasospasm produced by lysed blood and/or injury mediated by direct toxic effects of the lysed blood. The hsp70 induction and DNA nick end-labeling in the same regions suggests that lysed blood produces a spectrum of injury from HSP70 protein-labeled, reversibly injured cells to dead cells with fragmented DNA. Induction of the hsp70 stress gene and DNA nick end-labeling may be useful for evaluating the causes of injury, the spectrum of injury, and potential pharmacological therapies in experimental models of subarachnoid hemorrhage.

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PubMed1996

Induction of HSP70 in rat brain following subarachnoid hemorrhage produced by endovascular perforation.

Current experimental research on subarachnoid hemorrhage (SAH) has been limited by the lack of a small-animal model that physiologically resembles SAH and consistently demonstrates acute and delayed cellular injury. Recently, a model for inducing SAH by endovascular perforation of the internal carotid artery has been developed in the rat. This model physiologically resembles SAH. However, little histological data detailing cellular injury after SAH are available in this or other models. Using immunocytochemistry, the authors investigated the induction of the 70-kD heat shock protein, HSP70, a sensitive marker for cellular stress or injury in the brain, 1 and 5 days following endovascular SAH. The authors also used the conventional histological techniques of cresyl violet and hematoxylin and eosin staining to investigate cellular damage 1 and 5 days after the endovascular SAH. One day following the SAH, HSP70 was induced in all six animals examined in multiple anatomical regions, including the basal forebrain, thalamus, neocortex, striatum, and hippocampus. This HSP70 induction was observed in multiple vascular distributions bilaterally. Immunostaining with HSP70 occurred primarily in neurons but also was observed in glia and endothelium. Five days after the SAH, a similar but more intense pattern of HSP70 immunostaining was observed in all eight animals examined. Specifically, HSP70 immunoreactivity was observed in at least one region of the hippocampus more often at 5 days (six of eight animals) than at 1 day (one of six animals, p < 0.05, one-tailed Fisher's exact test). No HSP70 immunostaining was observed in control animals at 1 day or at 5 days. Conventional histology demonstrated foci of ischemic neuronal damage and cellular necrosis; however, HSP70 immunocytochemistry detailed cellular injury far better than conventional histology in all animals tested at both 1 day and 5 days. Our results demonstrate that HSP70 is induced in multiple regions and cell types 1 day and 5 days following endovascular SAH. Because ischemia is a known inducer of stress genes, the authors propose that acute and delayed ischemia are the processes responsible for the induction of HSP70 that was observed at 1 day and 5 days, respectively. Investigation of HSP70 induction following endovascular SAH may also serve as the basis for a new, inexpensive animal model to assess potential therapeutic interventions.

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PubMed1996

Focal hyperexpression of hemeoxygenase-1 protein and messenger RNA in rat brain caused by cellular stress following subarachnoid injections of lysed blood.

Induction of the hemeoxygenase-1 (ho-1) stress gene is of importance for rapid heme metabolism and protection against oxidative injury in vitro and in vivo. Although ho-1 expression is observed in glia following exposure to whole blood and oxyhemoglobin, expression is mild, and other stress genes are not induced simultaneously in this setting. Hemeoxygenase-1 can be induced by several other physiological stresses in addition to heme. In the brain, ho-1 induction has been observed in the penumbra following focal cerebral ischemia. Because lysed blood is a spasmogen, the authors studied focal hyperexpression of the ho-1 gene after injection of lysed blood, whole blood, or saline into the cisterna magna of adult rats. Immunocytochemical analysis of HO-1 was performed at 1, 2, 3, and 4 days after the injections. Because the 70-kD inducible heat shock protein (HSP70) is induced by cellular stress, alternate sections were immunostained for HSP70 to assess whether focal hyperexpression was a stress phenomenon. An oligonucleotide probe was also used for in situ hybridization to demonstrate that ho-1 messenger (m)RNA was present. Focal HO-1 immunostained areas were observed after lysed blood injection only and were located mainly in the basal cortex and cerebellar hemisphere, although focal hyperexpression was also found in many other regions. The intensity of staining and the number of regions were maximum at 1 day. Double-labeled immunofluorescence revealed that many HO-1-immunoreactive cells were microglia. The HSP70 immunostaining of adjacent sections from the same animals demonstrated focal regions of immunoreactivity whose topography corresponded exactly with the topography of the HO-1-immunostained areas. Conventional histology in regions of HO-1 hyperexpression was often normal. In situ hybridization using the same oligonucleotide demonstrated that ho-1 mRNA was induced in focal areas of forebrain and in large regions of cerebellum within 6 hours of injection. These results demonstrate that focal hyperexpression of the ho-1 stress gene occurs after lysed blood injection and appears to be an indicator of cellular stress and injury in regions in which infarction does not occur. These results also suggest that cellular injury that occurs after injection of lysed blood may go undetected using conventional histology. Although direct heme metabolism was not investigated, our results indicate that rapid metabolism of heme, both intracellular and extracellular, may prove to be beneficial after subarachnoid hemorrhage.

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PubMed1996

The stress gene response in brain.

Changes in gene expression in the brain in response to adverse conditions, such as ischemia or excitotoxin exposure, may be part of the injury process or represent an adaptive response which may be protective during subsequent stressful events. In this review we have considered the regulation, functions and potential relationships to the pathophysiology of ischemia of several major groups of stress-induced genes, including those of the M(r) 27,000, 32,000 (heme oxygenase), 70,000 and 90,000 heat shock protein families, the glucose-regulated proteins, glucose transporters and ubiquitin. Patterns of gene expression in several injury models, including focal and global ischemia, excitotoxin/ seizure-related injury and hyperthermia are reviewed. In vitro expression studies and the phenomenon of ischemic tolerance are also discussed. It is concluded that stress gene expression provides a useful marker of cellular injury, and that disjunction of mRNA and protein expression may be indicative of imminent death in cells which survive the initial insult. Though other stress proteins may play a role, it seems unlikely that neuronal hsp70 expression is a major contributor to ischemic tolerance.

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PubMed1995

Induction of HSP-70 after hyperosmotic opening of the blood-brain barrier in the rat.

The cellular response resulting from breakdown of the blood-brain barrier was evaluated 24 h after hyperosomotic infusion of mannitol into the internal carotid artery in the rat. Heat shock protein (HSP-70), a marker of cellular stress and/or injury, was induced in scattered patches of neurons and glia in regions of barrier breakdown. These findings suggest that osmotically induced breakdown of the blood-brain barrier may result in cell injury.

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PubMed1995

HSP70 heat shock protein induction following global ischemia in the rat.

Stress proteins, including the 70 kD heat shock protein (HSP70), are induced in injured cells. The present study was designed to characterize the cells injured by global ischemia in rat brain. Adult rats were subjected to forebrain ischemia using bilateral carotid occlusion and systemic hypotension. HSP70 protein immunostaining of brain sections was performed using the C92 monoclonal antibody one day later. HSP70 immunoreactive cells were found in many brain regions including cortex. HSP70 positive neurons in cortex were found in certain laminae, especially layers 2 and 3. Acid fuchsin positive neurons, cells presumed to be dead, were located only in the layers of cortex where HSP70 immunoreactive neurons were found and were infrequent compared to the large number of HSP70 positive neurons. HSP70 immunoreactive glial cells were detected at the margins of ischemic areas, and were mostly OX42 immunoreactive microglia plus some GFAP immunoreactive astrocytes. In some animals HSP70 stained bipolar cells were detected in the striatum and in white matter which may be type 2 astrocytes. These findings confirm that global ischemia injures microglia and astrocytes, and that cells in a given ischemic region sustain varying degrees of injury--from the HSP70 stained neurons that likely survive the ischemia to acid fuchsin stained cells that die.

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PubMed1995

Induction of heme oxygenase-1 (HO-1) after traumatic brain injury in the rat.

The induction of heme oxygenase-1 (HO-1), the 32 kDa heat shock protein, was examined in the traumatized rat brain. At 24 h after either mild or severe brain injury or sham surgery, HO-1 was immunolocalized in fixed sections of brain. After mild brain injury, hemorrhage was apparent in the subarachnoid space, external capsule and cerebellum. HO-1 was induced in similar areas in macrophages in the subarachnoid space and in glia in the cortex adjacent to the site of impact, the ipsilateral hippocampus, external capsule and cerebellum. After severe brain injury, extensive hemorrhage occurred in the external capsule, hippocampus and cerebellum. HO-1 was induced in glia in these areas of hemorrhage but was more extensive than that seen after mild injury and included the contralateral external capsule and hippocampus. These findings demonstrate remarkable induction of HO-1 in glia in the injured brain. Since heme is a potent inducer of HO-1, it is likely that the subarachnoid and/or intraparenchymal blood induced HO-1 in the glia where the heme was metabolized to biliverdin, iron, and carbon monoxide.

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PubMed1995

Metabolic mapping of rat striatum: somatotopic organization of sensorimotor activity.

Diseases that affect the striatum produce movement disorders, for which rats have been a useful model. To determine the organization of functional, neural activity in the rat striatum related to motor activity, we used electrical stimulation of the motor cortex and [14C]deoxyglucose autoradiography. The stimulation produced movements of each of three body regions. Both the motor and somatosensory cortex were activated. Image analysis was used to objectively localize peak activation and to provide a map for further stereotaxic and localization studies. In the anterior striatum, in the dorsolateral sector, regions of peak activation were well separated for each body region: the hindlimb peak activation was dorsomedial, the forelimb ventrolateral and vibrissae medial. Also, the activation fields were larger in anterior than in posterior striatum. Furthermore, activation ipsilateral to movement was present and the peak localization was offset from peaks contralateral to movement. In addition, there were activation regions in lateral striatum where body region representations may overlap. This is the first demonstration of a global striatal somatotopy that separates the limbs and vibrissae in rats. The functional average revealed by the deoxyglucose autoradiography showed a predominant isotropic or rod-like representation of sensorimotor activity for the limbs in striatum during movement and confirms aspects of the anatomy known for the corticostriate system in primates: metabolism was 'patchy,' and extended throughout long anteroposterior domains in striatum. These extensive and patchy arrangements suggest integrative, combinational and/or associative networks.

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PubMed1995

Apoptotic cell death of a temperature-sensitive central neuronal cell line.

A neuron-like cell line HS-2, derived from a primary fetal rat (E17) hippocampal cell culture using the temperature-sensitive SV 40 large T antigen, exhibits flat shape and grows well in culture medium with 5% fetal calf serum (FCS) at the permissive temperature (PT, 33.5 degrees C). At the non-permissive temperature (NPT, 38.5 degree C), many, but not all cells, have a neuronal shape with processes. The addition of dibutyryl-cAMP promotes the morphological changes in the cells to a neuron-like shape with long neurite-like processes and the cells exhibit neuron-specific enolase- and glutamic acid decarboxylase-immunoreactivity. Apoptotic cell death also occurs in these cultures at the NPT. DNA fragmentation and chromatin condensation that are characteristic of apoptosis occur within 8 h of being placed at the NPT. By 48 h after being placed at the NPT, the number of surviving cells decreases by 40% in the presence of 5% FCS. This cell line should be useful for investigating the mechanisms of 'programmed cell death' of neurons, which appears to occur during brain development and possibly in CNS degenerative diseases.

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PubMed1995

Cloning of rat grp75, an hsp70-family member, and its expression in normal and ischemic brain.

Following metabolic stress a variety of gene products are induced in cells in the brain, some of which may protect the tissue from subsequent stresses. The heat shock proteins (hsps), in particular hsp70, have been widely studied in this context, but evidence for the involvement of known hsps in protection of the CNS is inconclusive. We have therefore undertaken the search for other stress-induced proteins which may mitigate ischemic injury. Beginning with degenerate RT-PCR, we have isolated a rat-brain cDNA encoding a protein highly similar to human grp75, a mitochondrial member of the hsp70-family of stress proteins. It is also highly similar to two non-mitochondrial proteins; mortalin, a senescence-related gene product, and pbp74, a protein implicated in B-cell peptide processing. Sequence structure and phylogenetic analyses predict mitochondrial localization and induction by a calcium ionophore and glucose deprivation in PC12 cells support its identification as rat grp75. In situ analysis of normal brain reveals an unusual distribution, with very high expression in neurons of the basal forebrain, reticular and subthalamic nuclei, globus pallidus, amygdala and elsewhere. grp75-mRNA is upregulated following focal brain ischemia in a distinctive fashion. When the degree of injury is small, induction occurs in the area of injury, similar to the pattern observed for hsp70. However, when the injury is extensive, hsr is upregulated in neurons outside the ischemic area. The induction of grp75 may represent a sensitive marker of metabolically compromised tissue.

Amino Acid Sequence↗

PubMed1995

NMDA and D1 receptors mediate induction of c-fos and junB genes in striatum following morphine administration: implications for studies of memory.

The c-fos and junB immediate early genes (IEGs) were induced in neurons of the medial and ventral striatum following administration of morphine. The striatal induction of c-fos and junB mRNA and Fos protein was blocked by naloxone, the D1 dopamine (DA) receptor antagonists, SCH23390 and SCH39166, and the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, MK801. SCH23390 and MK801 did not block morphine induction of c-fos and junB in septum. Since the pattern of the morphine induction of c-fos and junB in striatum and nucleus accumbens was similar to that observed with cocaine and amphetamine [2,18,45,51], these data support current concepts that limbic striatum and nucleus accumbens are among the brain regions that mediate drug abuse [9,10,23,27,49]. If it is true that D1 receptors activate the CRE (cyclase response element) and NMDA receptors activate the SRE (serum response element) in the c-fos promoter [1], then this data suggests that serial activation of mu opiate, NMDA and D1 receptors on different neurons is required to induce Fos in striatal neurons with D1 Moreover, concurrent activation of NMDA and D1 receptors is required for Fos induction in striatal neurons. The Fos induced by this simultaneous activation of NMDA and D1 receptors should lead to long-term changes of gene expression that might also be involved in changes of brain circuits that could form the basis for 'memories' relating to prior exposure to addictive drugs.

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PubMed1995

Focal brain injury induces multiple immediate early genes encoding zinc finger transcription factors.

Focal brain injury is known to markedly induce the fos and jun families of immediate early genes (IEGs). This study employed in situ hybridization to examine the effects of focal brain injury, produced by the intracerebral injection of saline or ibotenic acid on the expression of IEGs encoding zinc finger transcription factors. Thirty minutes after the injections, NGFI-A, NGFI-B, NGFI-C, and egr-3 mRNAs were induced in dentate gyrus, hippocampal pyramidal cells, cerebral cortex, caudate-putamen and piriform cortex of the injured hemisphere. Nurr1 was induced in hippocampal pyramidal cells and dentate granule cells. After three hours the induction of NGFI-A, NGFI-B, NGFI-C and Nurr1 persisted in all brain regions except for the dentate granule cells. By six hours after injection mRNAs for most of the zinc finger genes had returned to control levels. However, the expression of egr-3 3 and 6 h after the injection was identical to that observed at 30 min after the injection and it was the only gene the expression of which persisted 6 h following the injections. Twenty-four hours after the injection, the expression of all five IEGs returned to control levels. In general, no gross differences in the IEG induction were observed between the animals injected with saline and ibotenic acid. Since these zinc finger genes were expressed in the same regions where fos and jun family members are induced by similar types of brain injury, it is suggested that these transcription factors may act in concert with Fos/Jun family members.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1995

Expression of c-fos and hsp70 mRNA after traumatic brain injury in transgenic mice overexpressing CuZn-superoxide dismutase.

The aim of this study was to determine the role of oxidative stress on c-fos and hsp70 gene expression in transgenic (Tg) mice overexpressing CuZn-superoxide dismutase (SOD-1) following traumatic brain injury (TBI). hsp70 mRNA, as investigated using in situ hybridization, was induced around the lesion at 4 and 24 h, but not at 1 and 48 h, in both Tg and non-transgenic (nTg) mice littermates. The degree of hsp70 induction was somewhat greater in nTg than Tg mice at 4 and 24 h after TBI. c-fos mRNA was induced throughout cortex, hippocampus, caudate putamen and the ventricular wall in Tg and nTg mice. TBI induced c-fos bilaterally in the cortex in both animals. There was a time-dependent difference in cortical c-fos expression between nTg and Tg mice. The induction of c-fos mRNA in the striatum was greater in nTg at 24 h and decreased in both animals by 48 h. Edema of the injured cortex was significantly attenuated in Tg mice at all time points (1-48 h). These data show that the degree of hsp70 induction and the degree, extent, and duration of c-fos induction produced by TBI are affected by levels of superoxide dismutase activity. It is proposed that superoxide radicals affect spreading depression and brain edema produced by TBI and that this effect may either directly or indirectly modulate the expression of the c-fos and hsp70 genes after TBI.

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PubMed1995

Anatomic patterns of Fos immunostaining in rat brain following systemic endotoxin administration.

To identify brain neurons that participate in the acute phase response, rat brains were examined immunocytochemically for Fos protein following the intravenous administration of bacterial endotoxin (lipopolysaccharide, LPS). Two to three hours after the injection of LPS, 150 micrograms/kg body weight, to adult male Long-Evans rats, a consistent anatomic pattern of Fos immunostained cell nuclei is seen. In the brain stem, prominant Fos immunostaining is induced in tyrosine hydroxylase immunoreactive neurons of the caudal ventral-lateral medulla (the A1 cell group), in both tyrosine hydroxylase positive and negative neurons of nu. tractus solitarius, in the parabrachial nu., and in a few neurons of the locus ceruleus. In the hypothalamus, endotoxin induces Fos expression in magnocellular neurons of the paraventricular and supraoptic nuclei and internuclear cell groups. A higher percentage of oxytocin-immunoreactive cells is double labeled for Fos nuclear immunostaining than vasopressin-immunoreactive cells. A minority of somatostatin immunoreactive periventricular hypothalamic neurons are Fos positive. Other hypothalamic nuclei that contain endotoxin-induced Fos nuclear immunostaining include the parvocellular neurons of the paraventricular nu., the dorsomedial and arcuate nuclei, the lateral hypothalamus, the dorsal hypothalamic area (zona incerta), and the median nucleus of the preoptic area. LPS induces numerous Fos-positive neurons in regions known to respond to a variety of stressful stimuli; these regions include the preoptic area, bed nucleus of the stria terminalis, lateral septum, and the central and medial nuclei of the amygdala. Moreover, Fos nuclear immunostaining is seen in neurons of circumventricular organs: the organum vasculosum of the lamina terminalis, the subfornical organ, and the area postrema. The maximum intensity of Fos nuclear immunostaining occurs 2-3 h after endotoxin administration and declines thereafter. It is attenuated by pretreatment with indomethacin, 25 mg/kg body weight Sc, or dexamethasone, 1 mg/kg IP. These observations are consistent with the participation of a variety of brain neuronal systems in the acute phase response and elucidate the functional neuroanatomy of that response at the cellular level.

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PubMed1995

Cerebellar toxicity of phencyclidine.

Phencyclidine (PCP), dizocilpine maleate (MK801), and other NMDA antagonists are toxic to neurons in the posterior cingulate and retrosplenial cortex. To determine if additional neurons are damaged, the distribution of microglial activation and 70 kDa heat shock protein (HSP70) induction was studied following the administration of PCP and MK801 to rats. PCP (10-50 mg/kg) induced microglial activation and neuronal HSP70 mRNA and protein expression in the posterior cingulate and retrosplenial cortex. In addition, coronal sections of the cerebellar vermis of PCP (50 mg/kg) treated rats contained vertical stripes of activated microglial in the molecular layer. In the sagittal plane, the microglial activation occurred in irregularly shaped patches, suggesting damage to Purkinje cells. In accord with this finding, PCP induced HSP70 protein and mRNA expression in Purkinje cells. Although there were relatively few foci of microglial activation and cells with HSP70 protein induction, HSP70 mRNA was detected in many Purkinje cells located throughout the cerebellar hemispheres as well as the vermis. MK801, at doses of 5-10 mg/kg, induced microglial activation and neuronal HSP70 mRNA and protein expression in the cingulate and retrosplenial cortex but not in the cerebellum. At the dose of 1 mg/kg MK801 induced HSP70 but did not consistently activate microglia. These data suggest that microglia are activated by MK801 doses that kill or severely damage neurons, whereas HSP70 is induced in "stressed" neurons at MK801 doses well below those that produce severe neurotoxicity. These observations suggest that PCP, but not MK801, is toxic to Purkinje cells and raise the question of whether NMDA antagonists or sigma ligands other than PCP are toxic to the cerebellum. Moreover, this study illustrates the usefulness of microglial activation and HSP70 induction as markers of neurotoxicity.

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