Single Electroconvulsive Seizures Research Articles

Sustained Ultrastructural Changes in Rat Hippocampal Formation After Repeated Electroconvulsive Seizures.

BackgroundElectroconvulsive therapy (ECT) is a highly effective and fast-acting treatment for depression used in the clinic. Its mechanism of therapeutic action remains uncertain. Previous studies have focused on documenting neuroplasticity in the early phase following electroconvulsive seizures (ECS), an animal model of ECT. Here, we investigate whether changes in synaptic plasticity and nonneuronal plasticity (vascular and mitochondria) are sustained 3 months after repeated ECS trials.MethodsECS or sham treatment was given daily for 1 day or 10 days to a genetic animal model of depression: the Flinders Sensitive and Resistant Line rats. Stereological principles were employed to quantify numbers of synapses and mitochondria as well as length of microvessels in the hippocampus 24 hours after a single ECS. Three months after 10 ECS treatments (1 per day for 10 days) and sham-treatment, brain-derived neurotrophic factor and vascular endothelial growth factor protein levels were quantified with immunohistochemistry.ResultsA single ECS treatment significantly increased the volume of hippocampal CA1-stratum radiatum, the total length of microvessels, mitochondria number, and synapse number. Observed changes were sustained as shown in the multiple ECS treatment group analyzed 3 months after the last of 10 ECS treatments.ConclusionA single ECS caused rapid effects of synaptic plasticity and nonneuronal plasticity, while repeated ECS induced long-lasting changes in the efficacy of synaptic plasticity and nonneuronal plasticity at least up to 3 months after ECS.

Electroconvulsive Seizure Alters the Expression and Daily Oscillation of Circadian Genes in the Rat Frontal Cortex.

ObjectiveElectroconvulsive therapy (ECT) is the most effective treatment for mood disorders. Accumulating evidence has suggested the important role of circadian genes in mood disorders. However, the effects of ECT on circadian genes have not been systemically investigated. MethodsWe examined the expression and daily oscillation of major circadian genes in the rat frontal cortex after electroconvulsive seizure (ECS). ResultsFirstly, mRNA and protein level were investigated at 24 hr after single ECS (E1X) and repeated ECS treatements for 10 days (E10X), which showed more remarkable changes after E10X than E1X. mRNA expression of Rorα, Bmal1, Clock, Per1, and Cry1 was decreased, while Rev-erbα expression was increased at 24 hr after E10X compared to sham. The proteins showed similar pattern of changes. Next, the effects on oscillation and rhythm properties (mesor, amplitude, and acrophase) were examined, which also showed more prominent changes after E10X than E1X. After E10X, mesor of Rorα, Bmal1, and Cry1 was reduced, and that of Rev-erbα was increased. Five genes, Rev-erbα, Bmal1, Per1, Per2, and Cry2, showed earlier acrophase after E10X. Conclusion The findings suggest that repeated ECS induces reduced expression and phase advance of major circadian genes in the in vivo rat frontal cortex.

Spatial memory impairment in Morris water maze after electroconvulsive seizures.

Electroconvulsive therapy (ECT) is one of the most efficient treatments for severe major depression, but some patients suffer from retrograde memory loss after treatment. Electroconvulsive seizures (ECS), an animal model of ECT, have repeatedly been shown to increase hippocampal neurogenesis, and multiple ECS treatments cause retrograde amnesia in hippocampus-dependent memory tasks. Since recent studies propose that addition of newborn hippocampal neurons might degrade existing memories, we investigated whether the memory impairment after multiple ECS treatments is a cumulative effect of repeated treatments, or if it is the result of a delayed effect after a single ECS. We used the hippocampus-dependent memory task Morris water maze (MWM) to evaluate spatial memory. Rats were exposed to an 8-day training paradigm before receiving either a single ECS or sham treatment and tested in the MWM 24 h, 72 h, or 7 days after this treatment, or multiple (four) ECS or sham treatments and tested 7 days after the first treatment. A single ECS treatment was not sufficient to cause retrograde amnesia whereas multiple ECS treatments strongly disrupted spatial memory in the MWM. The retrograde amnesia after multiple ECS is a cumulative effect of repeated treatments rather than a delayed effect after a single ECS.

Seizure-Induced Regulations of Amyloid-β, STEP61, and STEP61 Substrates Involved in Hippocampal Synaptic Plasticity.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline. Pathologic accumulation of soluble amyloid-β (Aβ) oligomers impairs synaptic plasticity and causes epileptic seizures, both of which contribute to cognitive dysfunction in AD. However, whether seizures could regulate Aβ-induced synaptic weakening remains unclear. Here we show that a single episode of electroconvulsive seizures (ECS) increased protein expression of membrane-associated STriatal-Enriched protein tyrosine Phosphatase (STEP61) and decreased tyrosine-phosphorylation of its substrates N-methyl D-aspartate receptor (NMDAR) subunit GluN2B and extracellular signal regulated kinase 1/2 (ERK1/2) in the rat hippocampus at 2 days following a single ECS. Interestingly, a significant decrease in ERK1/2 expression and an increase in APP and Aβ levels were observed at 3-4 days following a single ECS when STEP61 level returned to the baseline. Given that pathologic levels of Aβ increase STEP61 activity and STEP61-mediated dephosphorylation of GluN2B and ERK1/2 leads to NMDAR internalization and ERK1/2 inactivation, we propose that upregulation of STEP61 and downregulation of GluN2B and ERK1/2 phosphorylation mediate compensatory weakening of synaptic strength in response to acute enhancement of hippocampal network activity, whereas delayed decrease in ERK1/2 expression and increase in APP and Aβ expression may contribute to the maintenance of this synaptic weakening.

Potential roles for Homer1 and Spinophilin in the preventive effect of electroconvulsive seizures on stress-induced CA3c dendritic retraction in the hippocampus

Electroconvulsive therapy (ECT) remains the treatment of choice for patients with severe or drug-resistant depressive disorders, yet the mechanism behind its efficacy remains poorly characterized. In the present study, we used electroconvulsive seizures (ECS), an animal model of ECT, to identify proteins possibly involved in the preventive effect of ECS on stress-induced neuronal atrophy in the hippocampus. Rats were stressed daily using the 21-day 6h daily restraint stress paradigm and subjected to sham seizures, a single ECS on the last day of the restraint period or daily repeated seizures for 10 consecutive days during the end of the restraint period. Consistent with previous findings, dendritic atrophy was observed in the CA3c hippocampal region of chronically stressed rats. In addition, we confirmed our recent findings of increased spine density in the CA1 region following chronic restraint stress. The morphological alterations in the CA3c area were prevented by treatment with ECS. On the molecular level, we showed that the synaptic proteins Homer1 and Spinophilin are targeted by ECS. Repeated ECS blocked stress-induced up-regulation of Spinophilin protein levels and further increased the stress-induced up-regulation of Homer1. Given the roles of Spinophilin in the regulation of AMPA receptors and Homer1 in the regulation of metabotropic glutamate receptors (mGluRs), our data imply the existence of a mechanism where ECS regulate cell excitability by modulating AMPA receptor function and mGluR related calcium homeostasis. These molecular changes could potentially contribute to the mechanism induced by ECS which prevents the stress-induced morphological changes in the CA3c region.

Electroconvulsive seizure induces thrombospondin-1 in the adult rat hippocampus

Synaptic dysfunction has recently gained attention for its involvement in mood disorders. Electroconvulsive therapy (ECT) possibly plays a role in synaptic repair. However, the underlying mechanisms remain uncertain. Thrombospondin-1 (TSP-1), a member of the TSP family, is reported to be secreted by astrocytes and to regulate synaptogenesis. We investigated the effects of electroconvulsive seizure (ECS) on the expression of TSPs in the adult rat hippocampus. Single and repeated ECS significantly increased TSP-1 mRNA expression after 2h and returned to sham levels at 24h. Conversely, the TSP-2 and -4 mRNA levels did not change. Only repeated ECS induced TSP-1 proteins. ECS also induced glial fibrillary acidic protein (GFAP) expression. The GFAP expression occurred later than the TSP-1 mRNA expression following single ECS; however, it occurred earlier and was more persistent following repeated ECS. ECS had no effect on the α2δ-1 or neuroligin-1 expressions, both of which are TSP-1 receptors. Furthermore, chronic treatment with antidepressants did not induce the expression of TSP-1 or GFAP. These findings suggest that repeated ECS, but not chronic treatment with antidepressants, induces TSP-1 expression partially via the activation of astrocytes. Therefore, TSP-1 is possibly involved in the synaptogenic effects of ECS.

Genetic fate mapping of type-1 stem cell-dependent increase in newborn hippocampal neurons after electroconvulsive seizures

Electroconvulsive therapy (ECT) is a uniquely effective treatment for major depressive disorder. An increase in hippocampal neurogenesis is implicated in the recovery from depression. We used an inducible genetic mouse model in which only GFAP-expressing stem-like cells (type-1 cells) and their progeny are selectively labeled with the reporter protein β-galactosidase to track the process of neurogenesis in the dentate gyrus over 3 months following electroconvulsive seizures (ECS), the mouse equivalent of ECT. All ECS protocols tested induced a transient increase in type-1 cell divisions. While this led to an expansion of the type-1 cell pool after high-frequency ECS sessions for 5 consecutive days (5-ECS), asymmetric divisions drove neurogenesis by giving rise to Doublecortin (DCX)-expressing neuroblasts that matured into NeuN+ neurons. Significantly, the increase in newly generated DCX+ and NeuN+ cells after 5-ECS could be traced back to proliferating type-1 cells. Low-frequency continuation ECS (c-ECS) consisting of five single ECS sessions administered every 2 weeks resulted in a similar increase in newborn neurons as the high-frequency 5-ECS protocol. Moreover, the combination of 5-ECS and c-ECS led to a further significant increase in newborn neurons, suggesting a cellular mechanism responsible for the propitious effects of high-frequency ECT followed by continuation ECT in severely depressed patients. The ability of high- and low-frequency ECS to induce normally quiescent type-1 cells to proliferate and generate new neurons sets it apart from other antidepressant treatments and may underlie the superior clinical efficacy of ECT.

Electroconvulsive seizure, but not imipramine, rapidly up-regulates pro-BDNF and t-PA, leading to mature BDNF production, in the rat hippocampus

Electroconvulsive therapy is the most effective treatment for antidepressant-resistant depression, although its mechanism has not been fully elucidated. Previous studies have demonstrated that electroconvulsive seizures (ECS) induce expression of brain-derived neurotrophic factor (BDNF) in the rat hippocampus. However, in contrast with mature BDNF (mBDNF) known to have antidepressant effects, its precursor (pro-BDNF) has harmful effects on neurons. We therefore hypothesized that efficient processing of pro-BDNF is a critical requirement for the antidepressant effects of ECS. We found that single administration of ECS rapidly increased not only hippocampal levels of pro-BDNF but also those of prohormone convertase 1 (PC1) and tissue-plasminogen activator (t-PA), which are proteases involved in intra- and extracellular pro-BDNF processing, respectively. Interestingly, pro-BDNF and t-PA levels were increased in hippocampal synaptosomes after single ECS, suggesting their transport to secretory sites. In rats receiving 10-d repeated ECS, accumulation of pro-BDNF and a resultant increase in mBDNF levels were observed. While t-PA levels increased and accumulated following repeated ECS, PC1 levels did not, suggesting that intracellular processing capacity is limited. Finally, chronic administration of imipramine significantly increased mBDNF levels, but not pro-BDNF and protease levels, indicating that the therapeutic mechanism of imipramine differs from that of ECS. Taken together, these results suggest that, while intra- and extracellular proteases are involved in pro-BDNF processing in single ECS, t-PA plays a dominant role following repeated ECS. Such efficient pro-BDNF processing as well as strong induction of BDNF expression may contribute to the antidepressant effects of ECS.

Effects of repeated electroconvulsive seizure on cell proliferation in the rat hippocampus

Electroconvulsive therapy (ECT) is known as a successful treatment for severe depression. Despite great efforts, the biological mechanisms underlying the beneficial effects of ECT remain largely unclear. In this study, animals received a single, 10, or 20 applications of electroconvulsive seizure (ECS), and then cell proliferation and apoptosis were investigated in the subgranular zone (SGZ) of the dentate gyrus. We analyzed whether a series of ECSs could induce changes in the dentate gyrus in a dose-response fashion. A single-ECS seizure significantly increased cell proliferation in the SGZ by ∼2.3-fold compared to sham treatment. After 10 ECSs, a significant increase in cell proliferation was observed in the SGZ by ∼2.4-fold compared to sham treatment. Moreover, 10 ECSs induced a significant increase in cell proliferation by 1.3-fold compared to a single-ECS group. However, cell proliferation did not differ between the group with 20 ECSs and sham group. In addition, a significant increase in the number of apoptotic cells was found in the group with 10 ECSs, whereas no significant change in it was found in either a single ECS or 20 ECSs group compared to sham treatment. These findings indicate that the optimal number of treatments and duration of stimulation requires investigation. Further studies are needed to elucidate the intracellular mechanisms underlying both effective and excessive ECT.

Electroconvulsive seizure increases phosphorylation of PKC substrates, including GAP-43, MARCKS, and neurogranin, in rat brain

Protein kinase C (PKC) has been suggested as a molecular target related to the pathogenetic and therapeutic mechanisms of mood disorders in which electroconvulsive seizure (ECS) is effective. However, the reports concerning the effects of ECS on PKC are anecdotal and need further clarification. In this study, we examined the effects of ECS treatment on the phosphorylation of PKC substrates, including GAP-43, MARCKS, and neurogranin. Immunoblot using anti-p-PKC substrate antibodies revealed that a single ECS treatment induced temporal changes in the phosphorylation level of PKC substrates in rat brain, reflecting the effects on PKC activity. Phosphorylation of GAP-43 and MARCKS, representative PKC substrates related to synaptic remodeling, increased from 5 to 30 min, after a transient decrease at 0 min immediately after ECS, and returned to basal levels at 60 min in rat frontal cortex, hippocampus, and cerebellum. Phosphorylation of neurogranin, another PKC substrate, showed a similar pattern of temporal changes in the frontal cortex and hippocampus. Immunohistochemical analysis revealed that p-GAP-43 and p-MARCKS were densely stained throughout the neuronal cells of the prefrontal cortex and hippocampus, and the Purkinje cells of cerebellum, after ECS treatment. Brief and transient activation of PKC may be translated into long-term biochemical changes, resulting in synaptic plasticity. Taken together, the acute effects of ECS on PKC activity, which could be an underpinning of long-term biochemical changes induced by ECS, may contribute to understand the molecular mechanism of ECS.

Differential expression of synaptic vesicle proteins after repeated electroconvulsive seizures in rat frontal cortex and hippocampus

Electroconvulsive therapy (ECT) remains the treatment of choice for patients with severe or drug-resistant depressive disorders, yet the mechanism behind its efficacy and the effect on neurotransmission is essentially unknown. As synaptic vesicle proteins (SVPs) are required for vesicle fusion and neurotransmitter release, we have examined the effect of single and repeated electroconvulsive seizures (ECS), an animal model of ECT, on the expression of 14 SVPs in the rat frontal cortex and the hippocampus using quantitative real-time polymerase chain reaction (real-time qPCR). Only in the frontal cortex, the mRNA level of synapsin II was significantly upregulated after repeated ECS. In contrast, the mRNA levels of 6 of the 14 SVPs were significantly regulated in the hippocampus after ECS. We found that SNAP29 was upregulated and synaptotagmin III was downregulated after one single ECS in the hippocampus. Furthermore, SNAP29, synapsin I, synapsin III, VAMP2, and VAMP5 were significantly upregulated, whereas synaptotagmin III was significantly downregulated after repeated ECS in the hippocampus. We suggest that these genes are highly important in the long-term therapeutic effect of ECS, and thus it can be hypothesized that the SVPs are involved in the pathophysiology of depression.

Structure-related oxidative damage in rat brain after acute and chronic electroshock.

The role of oxidative stress in electroconvulsive therapy-related effects is not well studied. The purpose of this study was to determine oxidative stress parameters in several brain structures after a single electroconvulsive seizure or multiple electroconvulsive seizures. Rats were given either a single electroconvulsive shock or a series of eight electroconvulsive shocks. Brain regions were isolated, and levels of oxidative stress in the brain tissue (cortex, hippocampus, striatum and cerebellum) were measured. We demonstrated a decrease in lipid peroxidation and protein carbonyls in the hippocampus, cerebellum, and striatum several times after a single electroconvulsive shock or multiple electroconvulsive shocks. In contrast, lipid peroxidation increases both after a single electroconvulsive shock or multiple electroconvulsive shocks in cortex. In conclusion, we demonstrate an increase in oxidative damage in cortex, in contrast to a reduction of oxidative damage in hippocampus, striatum, and cerebellum.

Electroconvulsive seizures induce endothelial cell proliferation in adult rat hippocampus

Background Electroconvulsive seizures, an animal model for electroconvulsive treatment, induce a strong increase in neurogenesis in the dentate gyrus of adult rats. Hippocampal neurogenesis has previously been described as occurring in an angiogenic niche. This study examines the effect of electroconvulsive seizures on proliferation of vascular cells in rat hippocampus. Methods Rats were injected with bromodeoxyuridine to label proliferating cells in the dentate gyrus after single/multiple electroconvulsive seizures in a dose-response study and at various time points after single electroconvulsive seizures in a time-course study. Results A dose-response effect on the number of bromodeoxyuridine-labeled endothelial cells located in the granule cell layer, hilus, and molecular layer was noted, as was the case with the number of neural precursors in the subgranular zone. The time-course study revealed that endothelial cell and neural precursor proliferation occurred in concert in response to a single electroconvulsive seizure. Conclusions Our data suggest that in response to electroconvulsive seizures, endothelial cell and neural proliferation is coregulated. The increase in endothelial cell proliferation may act to support the increased neural proliferation and neuronal activity or vice versa, possibly leading to structural changes within the hippocampus of importance for the antidepressant effect of electroconvulsive seizures.

Electroconvulsive seizures increase hippocampal neurogenesis after chronic corticosterone treatment

Major depression is often associated with elevated glucocorticoid levels. High levels of glucocorticoids reduce neurogenesis in the adult rat hippocampus. Electroconvulsive seizures (ECS) can enhance neurogenesis, and we investigated the effects of ECS in rats where glucocorticoid levels were elevated in order to mimic conditions seen in depression. Rats given injections of corticosterone or vehicle for 21 days were at the end of this period treated with either a single or five daily ECSs. Proliferating cells were labelled with bromodeoxyuridine (BrdU). After 3 weeks, BrdU-positive cells in the dentate gyrus were quantified and analyzed for co-labelling with the neuronal marker neuron-specific nuclear protein (NeuN). In corticosterone-treated rats, neurogenesis was decreased by 75%. This was counteracted by a single ECS. Multiple ECS further increased neurogenesis and no significant differences in BrdU/NeuN positive cells were detected between corticosterone- and vehicle-treated rats given five ECS. Approximately 80% of the cells within the granule cell layer and 10% of the hilar cells were double-labelled with BrdU and NeuN. We therefore conclude that electroconvulsive seizures can increase hippocampal neurogenesis even in the presence of elevated levels of glucocorticoids. This further supports the hypothesis that induction of neurogenesis is an important event in the action of antidepressant treatment.

Increased neurogenesis in a model of electroconvulsive therapy

Background: Electroconvulsive therapy (ECT) is a widely used and efficient treatment modality in psychiatry, although the basis for its therapeutic effect is still unknown. Past research has shown seizure activity to be a regulator of neurogenesis in the adult brain. This study examines the effect of a single and multiple electroconvulsive seizures on neurogenesis in the rat dentate gyrus. Methods: Rats were given either a single or a series of 10 electroconvulsive seizures. At different times after the seizures, a marker of proliferating cells, Bromodeoxyuridine (BrdU), was administered to the animals. Subsequently, newborn cells positive for BrdU were counted in the dentate gyrus. Double staining with a neuron-specific marker indicated that the newborn cells displayed a neuronal phenotype. Results: A single electroconvulsive seizure significantly increased the number of new born cells in the dentate gyrus. These cells survived for at least 3 months. A series of seizures further increased neurogenesis, indicating a dose-dependent mechanism. Conclusions: We propose that generation of new neurons in the hippocampus may be an important neurobiologic element underlying the clinical effects of electroconvulsive seizures.

Repetitive electroconvulsive seizures induce activity of c-Jun N-terminal kinase and compartment-specific desensitization of c-Jun phosphorylation in the rat brain

Electroconvulsive seizures (ECS) are used for therapy of pharmacoresistent depression and are supposed to induce long-lasting neuronal alterations in morphology and gene expression. In this study, we have investigated the phosphorylation of the transcription factor protein c-Jun at its serine 73 residue by immunohistochemistry and the activity of the c-Jun N-terminal kinase 1 (JNK1) by immunocomplex assay following repetitive ECS in adult rats. In untreated controls, nuclear c-Jun immunoreactivity, but not N-terminal phosphorylation, was present in a variety of neuronal populations including the hippocampus, the temporobasal cortex and the amygdalar complex. Daily ECS for 1, 5 or 10 days (1×, 5× or 10× ECS) did not alter the expression of c-Jun but caused a substantial N-terminal phosphorylation of c-Jun (phospho-c-Jun). Nuclear phospho-c-Jun immunoreactivity was maximal within 15 min following ECS, and became absent after 30 min. The highest levels of phospho-c-Jun labeling were found after 1× ECS in the amygdalar complex, the dorsomedial hypothalamus and the piriform cortex. The inducibility of c-Jun N-terminal phosphorylation was preserved in the medial amygdala and piriform cortex, but significantly declined in the basal amygdala and medial hypothalamus with progressive ECS stimulation. One single ECS 3 or 5 days following 10× ECS yielded a pattern of phospho-c-Jun as seen following 10× ECS; thus, a lag of 5 days was not sufficient to provoke the initial level of N-terminal phosphorylation of c-Jun. In the dentate gyrus, c-Jun was not phosphorylated at any investigated time inspite of its high constitutive expression. In some contrast with this compartment-specific phosphorylation of c-Jun, immunocomplex assays revealed that the JNK1 activity was strongly enhanced in both amygdala and hippocampus. Our findings demonstrate that rapid JNK activation and phosphorylation of c-Jun as stand-by transcription factor characterize the beginning of neuroplastic changes, e.g., following ECS, a classic treatment of mental disorders. The N-terminal phosphorylation is compartment specific and can habituate following repetitive stimulation suggesting that the differential activation of the JNK/c-Jun axis is part of the neuronal strategy to integrate transynaptic excitation.

Differential Intracellular Sorting of Immediate Early Gene mRNAs Depends on Signals in the mRNA Sequence

This study characterizes the differential targeting of recently synthesized immediate early gene (IEG) mRNAs to neuronal cell bodies versus dendrites and tests the hypothesis that this targeting is based on signals in the encoded proteins. A single electroconvulsive seizure induces the expression of a number of IEG mRNAs in granule cells of the dentate gyrus. Most of these IEG mRNAs remain in the cell body, including two that are characterized in the present study (the mRNAs for NGFI-A and COX-2). In contrast, the mRNA for Arc moved rapidly into dendrites at an apparent rate of approximately 300 micron/hr. Inhibiting protein synthesis with cycloheximide did not disrupt the differential mRNA sorting, demonstrating that the differential targeting of mRNAs is not dependent on translation.

Signals that regulate astroglial gene expression: induction of GFAP mRNA following seizures or injury is blocked by protein synthesis inhibitors.

Previous studies have revealed that a single electroconvulsive seizure (ECS) strongly induces glial fibrillary acidic protein (GFAP) expression in astrocytes in the hippocampal dentate gyrus. The signals that trigger this induction are not known, but circumstantial evidence suggests the hypothesis that GFAP expression may be induced as a result of the induction of growth factor expression by dentate granule cells that also occurs as a result of the ECS and other types of seizures. The present study tests one prediction of this hypothesis by evaluating whether increases in GFAP mRNA levels after ECS are blocked by inhibiting protein synthesis at various times after the ECS. We report that the upregulation of GFAP expression following ECS is blocked by protein synthesis inhibitors given 5 min before or up to 12 h after a single ECS. This temporal gradient suggests an intermediate step involving the increased expression of a protein growth factor.

Rat nurr1 is prominently expressed in perirhinal cortex, and differentially induced in the hippocampal dentate gyrus by electroconvulsive vs. kindled seizures

We isolated a rat orphan nuclear hormone receptor from a brain cortex cDNA library. The sequence of the cDNA insert was 2154 bp with an open reading frame of 1794 bp encoding a putative protein of 598 amino acids and predicted molecular mass of 65 kDa. The deduced amino acid sequence showed a strong homology to the mouse nurr1 and human NOT1 orphan nuclear hormone receptors of the NGFI-B/nur77/NAK1 gene subfamily. We refer to this rat clone as r-nurr1. Northern blot analysis showed that r-nurr1 mRNA was highly expressed in the brain and moderately in the lung as a 4.0 kb transcript. A smaller transcript of 2.5 kb was also detected in the testes. The level of r-nurr1 transcript in the heart, skeletal muscle, liver, kidney and spleen was marginal. In situ hybridization showed that r-nurr1 mRNA was constitutively expressed in various regions of the CNS, particularly in the deeper layers (IV to VI) of the perirhinal cortex and area 2 of parietal cortex. We further evaluated the modulation of r-nurr1 expression in CNS by an electroconvulsive seizure (ECS) and by an amgydala-kindled seizure. A single ECS administered via earclip electrodes induced a rapid and transient increase of r-nurr1 mRNA in the granule cells of the dentate gyrus, being significant at 15 min after the seizure, maximal ≈1 h and back to baseline at 4 h. The amygdala kindled seizure revealed a less robust and restricted nurr-1 induction in the CNS, as only two of the four kindled animals showed a unilateral induction of nurr1 mRNA in the dentate gyrus. These results suggest that r-nurr1 is an immediate-early gene that is differentially induced by ECS vs. kindled seizures. In addition, as r-nurr1 is prominently expressed in the specific brain sites associated with memory acquisition and consolidation, it may play a role in memory processing.

High frequency transcranial magnetic stimulation mimics the effects of ECS in upregulating astroglial gene expression in the murine CNS

The present study evaluates the consequences of high frequency (25 hz) trans-cranial magnetic stimulation on the expression of glial fibrillary acidic protein (GFAP) in the murine CNS. Trains of transcranial magnetic stimulation (1–30 trains at 25 Hz, 10 s duration) were delivered to mice via 5-cm diameter round coils. The stimulation produced stimulus-locked motor responses but did not elicit behavioral seizures. GFAP mRNA levels were evaluated 12, 24, 36, 48 h, 4 days, and 8 days following stimulation by in situ hybridization. Following multiple 25 Hz trains, there were dramatic increases in the levels of GFAP mRNA in the hippocampal dentate gyrus; more modest increases were observed in the cerebral cortex. The selective increases in GFAP mRNA in the dentate gyrus were similar to those observed following single electroconvulsive seizures (ECS). These results indicate that trans-cranial magnetic stimulation can be used to modulate astroglial gene expression, inducing the first stage of a reactive response that is similar to what occurs following nervous system injury.