Induction Of C-fos mRNA Research Articles

The induction of BDNF and c-fos mRNA in the hippocampal formation after febrile seizures.

In this study we investigated the expression of brain-derived neurotrophic factor (BDNF) and c-fos mRNA in the hippocampal formation after febrile seizures (FSs) with in situ hybridization histochemistry using riboprobes. The induction of BDNF mRNA was firstly observed in the dentate gyrus at 30 min after FSs. The expression in the dentate gyrus peaked at 3 h and returned to basal level at 24 h. It was also observed in the CA3 of hippocampus from 2 to 3 h. The induction of c-fos mRNA was observed in the dentate gyrus at 30 min and 1 h. These observations suggest that BDNF and c-fos are the genes whose expression can be altered by FSs and might be related to pathologic alterations after FSs.

Functional components of basic fibroblast growth factor signaling that inhibit lung elastin gene expression

Previously, we have demonstrated that basic fibroblast growth factor (bFGF) decreases elastin gene transcription in confluent rat lung fibroblasts via the binding of a Fra-1-c-Jun heterodimer to an activator protein-1-cAMP response element in the distal region of the elastin promoter. In the present study, we show that bFGF activates the mitogen-activated protein kinase extracellular signal-regulated kinase 1/2, resulting in the translocation of phosphorylated extracellular signal-regulated kinase 1/2 into the nucleus followed by increased binding of Elk-1 to the serum response element of the c-Fos promoter, transient induction of c-Fos mRNA, and sustained induction of Fra-1 mRNA. The addition of PD-98059, an inhibitor of mitogen-activated protein kinase kinase, abrogates the bFGF-dependent repression of elastin mRNA expression. Comparative analyses of confluent and subconfluent fibroblast cultures reveal significant differences in elastin mRNA levels and activator protein-1 protein factors involved in the regulation of elastin transcription. These findings suggest that bFGF modulates specific cellular events that are dependent on the state of the cell and provide a rationale for the differential responses that can be expected in development and injury or repair situations.

Stimulation of DNA synthesis and c-fos mRNA expression in primary rat hepatocytes by estrogens.

The mechanism(s) of tumour promotion in liver by estrogens is not well understood although growth stimulation is known to be one important element of their action. As a basis for studying mechanisms of growth control by estrogens, effects of both natural and synthetic estrogens on DNA synthesis and protooncogene c-fos mRNA expression were examined in primary cultures of normal rat hepatocytes. 17beta-Estradiol (E(2)) alone was stimulatory and exhibited dramatic synergism with epidermal growth factor (EGF) in stimulating DNA synthesis. All estrogens tested (natural, synthetic, steroidal and non-steroidal) exhibited an ability to stimulate hepatocyte DNA synthesis. This appears to correlate with their ability to induce c-fos mRNA expression. In contrast to a non-estrogenic liver tumour promoter, phenobarbital, insulin is not permissive for the growth-stimulatory action of E(2). Dexamethasone, which is required for stimulation of DNA synthesis by the non-estrogenic tumour promoter alpha-hexachlorocyclohexane and tetradecanoylphorbol acetate, completely blocked E(2)-stimulated DNA synthesis. Such differential requirements for auxiliary factors suggests that estrogen and other non-estrogenic liver tumour promoters act via distinct mechanisms in stimulating hepatocyte DNA synthesis. E(2) alone had no effect, but when in combination with EGF significantly induced c-fos mRNA expression at early times in culture (maximal at 10 h in culture). Such findings, coupled with the observations that (i) E(2) and EGF were synergistic in growth stimulation, (ii) estrogen receptor levels are higher at early times in culture and (iii) the growth-stimulatory ability of E(2) is limited to 4-24 h in culture, support the notion that in hepatocytes E(2) acts via the estrogen receptor to transactivate c-fos expression (an interaction with EGF), which ultimately culminates in enhanced DNA synthesis. Dexamethasone did not block E(2)-induced c-fos gene expression, suggesting that it acts in a pathway(s) distal to activation of fos gene expression. The possible inhibitory mechanisms of action of dexamethasone on E(2)-stimulated DNA synthesis are discussed.

Emotional stress activates MAP kinase in the rat heart

Emotional stress evoked by immobilization of the rat induces c-fos mRNA or other immediate early genes. This response is mediated by activation of α- and β-adrenoceptors, through mechanisms that have not yet been elucidated. Here we show that immobilization stress activates p44/p42 Mitogen-Activated Protein kinase (p44/p42 MAP kinase, Erk1/Erk2). Pretreatment with the β1-blocker, metoprolol, did not inhibit the activation of stress-induced MAP kinase, while blockage of the α1-adrenoceptor by pretreatment with α1-blocker, prazosin or the α/β-blocker, amosulalol, attenuated the activation. Application of the α1-agonist, phenylephrine, but not the β-agonist, isoproterenol, to the perfused rat heart elicited MAP activation. Thus, emotional stress activates the α1-adrenoceptor-mediated MAP kinase pathway, whereas the pathway of the response mediated by the β-adrenoceptor remains unknown.

Induction of stereotypy in dopamine-deficient mice requires striatal D1 receptor activation.

Motor stereotypies are abnormally repetitive behaviors that can develop with excessive dopaminergic stimulation and are features of some neurologic disorders. To investigate the mechanisms required for the induction of stereotypy, we examined the responses of dopamine-deficient (DD) mice to increasing doses of the dopamine precursor L-DOPA. DD mice lack the ability to synthesize dopamine (DA) specifically in dopaminergic neurons yet exhibit robust hyperlocomotion relative to wild-type (WT) mice when treated with L-DOPA, which restores striatal DA tissue content to approximately 10% of WT levels. To further elevate brain DA content in DD mice, we administered the peripheral L-amino acid decarboxylase inhibitor carbidopa along with L-DOPA (C/l-DOPA). When striatal DA levels reached >50% of WT levels, a transition from hyperlocomotion to intense, focused stereotypy was observed that was correlated with an induction of c-fos mRNA in the ventrolateral and central striatum as well as the somatosensory cortex. WT mice were unaffected by C/L-DOPA treatments. A D1, but not a D2, receptor antagonist attenuated both the C/L-DOPA-induced stereotypy and the c-fos induction. Consistent with these results, stereotypy could be induced in DD mice by a D1, but not by a D2, receptor agonist, with neither agonist inducing stereotypy in WT mice. Intrastriatal injection of a D1 receptor antagonist ameliorated the stereotypy and c-fos induction by C/L-DOPA. These results indicate that activation of D1 receptors on a specific population of striatal neurons is required for the induction of stereotypy in DD mice.

Chronic treatment with certain antipsychotic drugs preserves upregulation of regulator of G-protein signalling 2 mRNA in rat striatum as opposed to c-fos mRNA

Quantitative in situ hybridization on rat coronal brain sections with radiolabelled oligonucleotide probes was performed to investigate the effects of antipsychotic drugs on mRNA levels of regulator of G-protein signalling (RGS) 2 and c-fos. This study demonstrated a similar increase of RGS2 mRNA level in the striatum upon both a single and a 21-day treatment with either haloperidol (2 mg/kg) or risperidone (7.5 mg/kg) in contrast to clozapine (20 mg/kg). Otherwise, the acute c-fos mRNA induction in the striatum was abolished by 74 to 89% upon chronic treatment with either haloperidol or risperidone. In conclusion, the induction of RGS2 mRNA in the striatum, in contrast to the immediate early gene c-fos mRNA, is preserved upon chronic treatment with haloperidol and risperidone.

Cycles of Transcription and Translation Do Not Comprise the Gonadotropin-Releasing Hormone Pulse Generator in GT1 Cells

Neural control of reproduction is achieved through episodic GnRH secretion, but little is known about the molecular mechanisms underlying pulse generation. The ultradian time domain of GnRH release suggests mechanisms ranging from macromolecular synthesis to posttranslational modification could be involved. We tested if messenger RNA (mRNA) or protein synthesis are components of the pulse generator by determining the effects of transcription and translation inhibitors on episodic GnRH release from immortalized GT1–1 GnRH neurons. Time course and efficacy of transcription and translation blockade were assessed by determining the ability of specific inhibitors to block the robust, rapid induction of c-fos mRNA or protein accumulation by forskolin (10 μm). The transcription inhibitors actinomycin D (ACT-D, 20 μm) or 5,6-dichlorobenzimidazole riboside (DRB, 100 μm), or the translation inhibitors anisomycin (ANI, 10 μm) or puromycin (PUR, 10 μm) were applied to GT1–1 cells 30, 15, or 0 min before forskolin. Northern and Western blots revealed blockade of transcription and translation was rapid and essentially complete. GT1–1 cells were perifused for a 90- to 120-min control period then for 100–130 min with vehicle or inhibitor to examine pulsatile GnRH secretion. GnRH interpeak intervals, peak amplitude, and peak area were not different between control and experimental periods of cells treated with vehicle (n = 15), ACT-D (n = 10), DRB (n = 6), ANI (n = 8), and PUR (n = 6; P > 0.05). This study presents the first clear evidence that the series of reactions resulting in secretion of a GnRH pulse do not include cycles of transcription and translation. Although these mechanisms would be required to replenish components of the pulse generator, they are not integral components of this oscillator. We hypothesize that posttranslational events underlie episodic GnRH release in GT1–1 cells.

Cycles of transcription and translation do not comprise the gonadotropin-releasing hormone pulse generator in GT1 cells.

Neural control of reproduction is achieved through episodic GnRH secretion, but little is known about the molecular mechanisms underlying pulse generation. The ultradian time domain of GnRH release suggests mechanisms ranging from macromolecular synthesis to posttranslational modification could be involved. We tested if messenger RNA (mRNA) or protein synthesis are components of the pulse generator by determining the effects of transcription and translation inhibitors on episodic GnRH release from immortalized GT1-1 GnRH neurons. Time course and efficacy of transcription and translation blockade were assessed by determining the ability of specific inhibitors to block the robust, rapid induction of c-fos mRNA or protein accumulation by forskolin (10 microM). The transcription inhibitors actinomycin D (ACT-D, 20 microM) or 5,6-dichlorobenzimidazole riboside (DRB, 100 microM), or the translation inhibitors anisomycin (ANI, 10 microM) or puromycin (PUR, 10 microM) were applied to GT1-1 cells 30, 15, or 0 min before forskolin. Northern and Western blots revealed blockade of transcription and translation was rapid and essentially complete. GT1-1 cells were perifused for a 90- to 120-min control period then for 100-130 min with vehicle or inhibitor to examine pulsatile GnRH secretion. GnRH interpeak intervals, peak amplitude, and peak area were not different between control and experimental periods of cells treated with vehicle (n = 15), ACT-D (n = 10), DRB (n = 6), ANI (n = 8), and PUR (n = 6; P > 0.05). This study presents the first clear evidence that the series of reactions resulting in secretion of a GnRH pulse do not include cycles of transcription and translation. Although these mechanisms would be required to replenish components of the pulse generator, they are not integral components of this oscillator. We hypothesize that posttranslational events underlie episodic GnRH release in GT1-1 cells.

Mapping of c-fos gene expression in the brain during morphine dependence and precipitated withdrawal, and phenotypic identification of the striatal neurons involved.

The c-fos gene is expressed in the central nervous system in response to various neuronal stimuli. Using in situ hybridization, we examined the effects of chronic morphine treatment and withdrawal on c-fos mRNA in the rat brain, and particularly within identified striatal neurons. Morphine dependence was induced by subcutaneous implantation of two pellets of morphine for 6 days and withdrawal was precipitated by administration of naltrexone. Placebo animals and morphine-dependent rats showed a very weak c-fos mRNA expression in all the structures studied. Our study emphasized the spatial variations in c-fos mRNA expression, and also revealed a peak expression of c-fos mRNA at 1 h after naltrexone-precipitated withdrawal in the projection areas of dopaminergic neurons, noradrenergic neurons and in several regions expressing opiate receptors. Interestingly, morphine withdrawal induces c-fos mRNA expression in the two efferent populations of the striatum (i.e. striatonigral and striatopallidal neurons) both in the caudate putamen and nucleus accumbens. Moreover, the proportions of activated neurons during morphine withdrawal are different in the caudate putamen (mostly in striatopallidal neurons) and in the shell and core parts of the nucleus accumbens (mostly in striatonigral neurons). The activation of striatopallidal neurons suggests a predominant dopaminergic regulation on c-fos gene expression in the striatum during withdrawal. On the contrary, c-fos induction in striatonigral neurons during withdrawal seems to involve a more complex regulation like opioid-dopamine interactions via the mu opioid receptor and the D1 dopamine receptor coexpressed on this neuronal population or the implication of other neurotransmitter systems.

Distribution of c-fos mRNA in the brain following intracerebroventricular injection of nitric oxide (NO)-releasing compounds: possible role of NO in central cardiovascular regulation.

We injected nitric oxide (NO)-releasing compounds and NO synthase (NOS) inhibitors into the brains of conscious, freely moving rats and measured the effects on mean arterial blood pressure (MAP) and heart rate, as well as on the expression of c-fos mRNA, neuronal NOS (nNOS) mRNA and NADPH-diaphorase, an indicator of NOS activity. When administered i.c.v., the NO donor, NOC-18, caused a significant fall in MAP and heart rate, whereas the NOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME), induced a significant rise in MAP. The same dose of NOC-18 or L-NAME when administered i.v. did not affect MAP and heart rate. Centrally administered NOC-18 induced c-fos mRNA expression in several regions of the brain involved in the baroreceptor response, including the nucleus of the solitary tract, the area postrema and the rostral ventrolateral medulla, as well as areas involved in the integration of autonomic, neuroendocrine and behavioural responses, including the medial preoptic area, the organum vasculosum lamina terminalis, the bed nucleus of stria terminalis, the paraventricular nucleus (PVN), the supraoptic nucleus (SON), the central nucleus of amygdala (CeA) and the locus coeruleus. Most of the areas that expressed c-fos also contained nNOS mRNA and/or NADPH-d-positive neurones and fibres. i.c.v. injection of L-NAME induced c-fos mRNA expression in PVN, SON, locus coeruleus and NTS, suggesting a tonic inhibition of neuronal activity by NO or stimulation of neuronal activity by endogenous NO. i.v. injection of NOC-18 or L-NAME did not induce any significant c-fos mRNA expression in rat brain. These results demonstrate that NO acts directly in the brain to reduce the systemic blood pressure, and that the endogenous NO pathway may play a role in cardiovascular and autonomic regulation by modulating neuronal activities in discrete regions of the brain.

C-Fos expression by dopaminergic receptor activation in rat hippocampal neurons.

While dopamine is likely to modulate hippocampal synaptic plasticity, there has been little information about how dopamine affects synaptic transmission in the hippocampus. The expression of IEGs including c-fos has been associated with late phase LTP in the CA1 region of the hippocampus. The induction of c-fos by dopaminergic receptor activation in the rat hippocampus was investigated by using semiquantitative RT-PCR and immunocytochemistry. The hippocampal slices which were not treated with dopamine showed little expression of c-fos mRNA. However, the induction of c-fos mRNA was detected as early as 5 min after dopamine treatment, peaked at 60 min, and remained elevated 5 h after treatment. Temporal profiles of increases in c-fos mRNA by R(+)-SKF-38393 (50 microM) and forskolin (50 microM) were similar to that of dopamine. An increase in [cAMP] was observed in dopamine-, SKF-, or forskolin-treated hippocampal slices. By immunocytochemical studies, control hippocampal cells showed little expression of c-Fos immunoreactivity. However, when cells were treated with dopamine, an increase in the expression of c-Fos immunoreactivity was observed after treatment for 2 h. The treatment of hippocampal neurons with R(+)-SKF38393 (50 microM) or forskolin (50 microM) also induced a significant increase in c-Fos expression. These results indicate that the dopamine D1 receptor-mediated cAMP dependent pathway is associated with the expression of c-Fos in the hippocampal neurons. These data are consistent with the possible role of endogenous dopamine on synaptic plasticity via the regulation of gene expression. Furthermore, these results imply that dopamine might control the process of memory storage in the hippocampus through gene expression.

C-Fos Expression by Dopaminergic Receptor Activation in Rat Hippocampal Neurons

While dopamine is likely to modulate hippocampal synaptic plasticity, there has been little information about how dopamine affects synaptic transmission in the hippocampus. The expression of IEGs including c-fos has been associated with late phase LTP in the CA1 region of the hippocampus. The induction of c-fos by dopaminergic receptor activation in the rat hippocampus was investigated by using semiquantitative RT-PCR and immuno-cytochemistry. The hippocampal slices which were not treated with dopamine showed little expression of c-fos mRNA. However, the induction of c-fos mRNA was detected as early as 5 min after dopamine treatment, peaked at 60 min, and remained elevated 5 h after treatment. Temporal profiles of increases in c-fos mRNA by R(+)-SKF-38393 (50 μM) and forskolin (50 μM) were similar to that of dopamine. An increase in [cAMP] was observed in dopamine-, SKF-, or forskolin-treated hippocampal slices. By immunocytochemical studies, control hippocampal cells showed little expression of c-Fos immunoreactivity. However, when cells were treated with dopamine, an increase in the expression of c-Fos immunoreactivity was observed after treatment for 2 h. The treatment of hippocampal neurons with R(+)-SKF38393 (50 μM) or forskolin (50 μM) also induced a significant increase in c-Fos expression. These results indicate that the dopamine D1 receptor-mediated cAMP dependant pathway is associated with the expression of c-Fos in the hippocampal neurons. These data are consistent with the possible role of endogenous dopamine on synaptic plasticity via the regulation of gene expression. Furthermore, these results imply that dopamine might control the process of memory storage in the hippocampus through gene expression.

Sphingosine-1-phosphate, lysophosphatidic acid, and sphingosylphosphorylcholine induce c-fos mRNA expression in C6 glioma cells

Sphingosine-1-phosphate, lysophosphatidic acid, and sphingosylphosphorylcholine induce c-fos mRNA expression in C6 glioma cells

Induction of the c-jun protooncogene expression by areca nut extract and arecoline on oral mucosal fibroblasts.

To investigate the mechanisms of areca quid (AQ)-induced carcinogenesis, expression of c-fos and c-jun protooncogenes was examined in human oral mucosal fibroblasts after exposure to areca nut extracts (ANE) or arecoline. We found that treatment of cells with 200 microg/ml ANE or 10 microg/ml arecoline for 1 h induced about three-fold increase in c-jun mRNA levels. This increase was transient and the level of c-jun mRNAs returned rapidly to control levels thereafter. However, ANE and arecoline did not induce c-fos mRNA expression at detectable levels. During AQ chewing, oral mucosal cells are continuously stimulated by ANE and arecoline. Persistent induction of the c-jun protooncogene by ANE and arecoline may be one of the mechanisms in the carcinogenesis of oral squamous cell carcinoma in Taiwan. Furthermore, we observed that pre-incubation of cells with either N-acetyl-cysteine [a glutathione (GSH) precursor] or L-buthionine-S,R-sulfoximine (a specific inhibitor of GSH biosynthesis) had a minimal effect on arecoline-induced c-jun expression. Therefore, arecoline-induced c-jun expression is independent of GSH depletion.

Impaired response to hepatocyte growth factor in FRTL-5 rat thyroid cells expressing a functional hepatocyte growth factor receptor.

The FRTL-5 rat thyroid cell line is widely used for studies of thyrocyte function and growth. The objective of the present study was to investigate the effects of hepatocyte growth factor (HGF) on FRTL-5 cells. HGF has previously been known to be a potent regulator of thyrocyte growth and differentiation. Met, the receptor for HGF was expressed in FRTL-5 cells, as well as in primary cultures of porcine thyrocytes included in the study as control. On HGF stimulation Met was tyrosine phosphorylated in both porcine and FRTL-5 cells, indicating an activation of the receptor. Addition of HGF induced changes of cell shape, scattering and proliferation of the porcine thyrocytes, but not in the FRTL-5 cells; yet, a functional coupling of Met to the p85 subunit of the phosphatidylinositol-3'-kinase (PI3'-K) in coprecipitation experiments, formation of focal adhesions detected in immunofluorescence staining with an antivinculin antibody, and induction of c-fos mRNA in Northern blot analysis was observed in FRTL-5 cells, showing a transduction of the HGF/Met signal. In summary, despite the expression of apparently functional Met, the FRTL-5 cells are unable to properly respond to HGF.

Characterization of Audiogenic-Like Seizures in Naive Rats Evoked by Activation of AMPA and NMDA Receptors in the Inferior Colliculus

The role of glutamate receptors in the inferior colliculus (IC) in audiogenic and audiogenic-like seizures was investigated in adult rats with transient neonatal hypothyroidism by 0.02% propylthiouracil (PTU) treatment through mother's milk (PTU rats) and in naive rats treated intracisternally with N-methyl-d-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazole-proprionic acid (AMPA), or cyclothiazide, an inhibitor of rapid AMPA receptor desensitization. All rats showed audiogenic or audiogenic-like seizures characterized by running fit (RF) and generalized tonic–clonic seizures (GTCS). While systemically administered MK-801 inhibited GTCS, intracisternally administered NBQX inhibited RF and GTCS in both audiogenic and audiogenic-like seizures. Auditory stimulation shortened the latency to GTCS induced by AMPA, but not NMDA, at a subclinical dose and further elongated the shortened duration of RF, but not GTCS, induced by MK-801 pretreatment. Furthermore, Northern blot analysis was used to evaluate the expression of the immediate-early gene c-fos in the IC following induction of audiogenic or audiogenic-like seizures. The significant induction of c-fos mRNA by audiogenic seizures in PTU rats or by AMPA- or cyclothiazide-induced seizures in naive rats was prominent in the IC. MK-801 suppressed c-fos mRNA expression in the IC induced by audiogenic seizures in PTU rats or by AMPA-induced seizures in naive rats. NBQX suppressed the expression of c-fos mRNA in the IC induced by AMPA-induced seizures but did not suppress c-fos mRNA in PTU rats or rats with cyclothiazide-induced seizures. Auditory stimuli failed to affect c-fos mRNA induction by AMPA. The present study suggests that audiogenic-like seizures can be reproduced by glutamate receptor agonists in which AMPA receptors are primarily linked to the initiation of audiogenic seizures (RF) while NMDA receptors presumably located within the IC are involved in the propagation of GTCS in audiogenic seizures.

Neuroprotective agent chlomethiazole attenuates c-fos, c-jun, and AP-1 activation through inhibition of p38 MAP kinase.

Recent evidence suggests that stress-activated protein kinases expressed in glial cells have very important roles during cerebral ischemia. The neuroprotective agent chlomethiazole, which is known to enhance the conductance at the GABA(A) receptor complex, is presently in clinical trials for the treatment of severe stroke. Here the authors suggested that chlormethiazole has anti-inflammatory properties because it potently and selectively inhibited p38 mitogen-activated protein (MAP) kinase in primary cortical glial cultures. The inhibition of p38 MAP kinase resulted in the attenuation of the induction of c-fos and c-jun mRNA and AP-1 DNA binding by lipopolysaccharide (LPS). In addition, chlomethiazole inhibited the activation of an AP-1-dependent luciferase reporter plasmid in SK-N-MC human neuroblastoma cells in response to glutamate. Chlomethiazole inhibited the p38 MAP kinase activity as revealed by the decrease in the LPS-induced phosphorylation of the substrates ATF-2 and hsp27, whereas the phosphorylation status of the p38 MAP kinase itself was unaffected. Interestingly, chlomethiazole exhibited an IC(50) of approximately 2 micromol/L for inhibition of c-fos mRNA expression, indicating 25 to 75 times higher potency than reported EC(50) values for enhancing GABA(A) chloride currents. The results indicated a novel mechanism of action of chlomethiazole, and provided support for a distinctive role of p38 MAP kinase in cerebral ischemia.

Distribution and initiation of seizure activity in a rat brain with subcortical band heterotopia.

Misplaced (heterotopic) cortical neurons are a common feature of developmental epilepsies. To better understand seizure disorders associated with cortical heterotopia, the sites of aberrant discharge activity were investigated in vivo and in vitro in a seizure-prone mutant rat (tish) exhibiting subcortical band heterotopia. Depth electrode recordings and postmortem assessment of regional c-fos mRNA levels were used to characterize the distribution of aberrant discharge activity during spontaneous seizures in vivo. Electrophysiologic recordings of spontaneous and evoked activity also were performed by using in vitro brain slices from the tish rat treated with proconvulsant drugs (penicillin and 4-aminopyridine). Depth electrode recordings demonstrate that seizure activity begins almost simultaneously in the normotopic and heterotopic areas of the tish neocortex. Spontaneous seizures induce c-fos mRNA in normotopic and heterotopic neocortical areas, and limbic regions. The threshold concentrations of proconvulsant drugs for inducing epileptiform spiking were similar in the normotopic and heterotopic areas of tish brain slices. Manipulations that blocked communication between the normotopic and heterotopic areas of the cortex inhibited spiking in the heterotopic, but not the normotopic, area of the cortex. These findings indicate that aberrant discharge activity occurs in normotopic and heterotopic areas of the neocortex, and in certain limbic regions during spontaneous seizures in the tish rat. Normotopic neurons are more prone to exhibit epileptiform activity than are heterotopic neurons in the tish cortex, and heterotopic neurons are recruited into spiking by activity initiated in normotopic neurons. The findings indicate that seizures in the tish brain primarily involve telencephalic structures, and suggest that normotopic neurons are responsible for initiating seizures in the dysplastic neocortex.

Expression of proto-oncogenes in bovine preimplantation blastocysts.

Proto-oncogenes are involved in the regulation of gene expression, for example after ligand binding to growth factor receptors. Expression of the proto-oncogenes c-fos, c-jun, c-ha-ras and c-myc was studied in in vivo grown and in vitro cultured bovine preimplantation blastocysts employing RT-PCR, ribonuclease protection assay and immunohistochemistry. Thirteen- and 14- day-old preimplantation blastocysts, i.e. stages before and during trophoblast elongation, were used. In in vivo-grown blastocysts c-fos, c-jun and c-ha-ras transcripts as well as c-Fos, c-Jun and c-Myc proteins were detected in all stages studied. Cultured blastocysts were treated with 10 nM epidermal growth factor and 10 nM transforming growth factor-alpha simultaneously. Epidermal growth factor and transforming growth factor-alpha treatment induced c-fos mRNA and c-Myc protein expression. The induction of downstream targets of the epidermal growth factor receptor by epidermal growth factor and transforming growth factor-alpha indicates a functional epidermal growth factor signal transduction pathway in elongating bovine blastocysts.

CP-101,606, an NR2B subunit selective NMDA receptor antagonist, inhibits NMDA and injury induced c-fos expression and cortical spreading depression in rodents

(1S,2S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (CP-101,606) is a noncompetitive antagonist of N-methyl-D-aspartate (NMDA) receptors containing the NR2B subunit. This compound was used to investigate the role of NR2B containing receptors in three responses to NMDA receptor activation in vivo. In mouse, CP-101,606 completely inhibited increases in fos-like immunoreactivity in dentate gyrus caused by a subconvulsant intraperitoneal dose of NMDA. In rat, the compound completely blocked cortical c-fos mRNA induction following focal injury in parietal cortex and the initiation and propagation of electrically induced cortical spreading depression. Inhibition of these responses by CP-101,606 indicates that c-fos induction and cortical spreading depression are dependent on activation of NMDA receptors containing the NR2B subunit. Since NMDA receptor dependent c-fos induction and cortical spreading depression may contribute to neuron loss after focal CNS injury, inhibition of these responses by CP-101,606 may contribute to the neuroprotective efficacy of the compound.