Meteorin Alleviates Paclitaxel-Induced Peripheral Neuropathic Pain in Mice.

Chemotherapy-induced peripheral neuropathy is a challenging condition to treat, and arises due to severe, dose-limiting toxicity of chemotherapeutic drugs such as paclitaxel. This often results in debilitating sensory and motor deficits that are not effectively prevented or alleviated by existing therapeutic interventions. Recent studies have demonstrated the therapeutic effects of Meteorin, a neurotrophic factor, in reversing neuropathic pain in rodent models of peripheral nerve injury induced by physical trauma. Here, we sought to investigate the potential antinociceptive effects of recombinant mouse Meteorin (rmMeteorin) using a paclitaxel-induced peripheral neuropathy model in male and female mice. Paclitaxel treatment (4 × 4 mg/kg, i.p.) induced hind paw mechanical hypersensitivity by day 8 after treatment. Thereafter, in a reversal dosing paradigm, five repeated injections of rmMeteorin (.5 and 1.8 mg/kg s.c. respectively) administered over 9 days produced a significant and long-lasting attenuation of mechanical hypersensitivity in both sexes. Additionally, administration of rmMeteorin ( .5 and 1.8 mg/kg), initiated before and during paclitaxel treatment (prevention dosing paradigm), reduced the establishment of hind paw mechanical hypersensitivity. Repeated systemic administration of rmMeteorin in both dosing paradigms decreased histochemical signs of satellite glial cell reactivity as measured by glutamine synthetase and connexin 43 protein expression in the dorsal root ganglion. Additionally, in the prevention administration paradigm rmMeteorin had a protective effect against paclitaxel-induced loss of intraepidermal nerve fibers. Our findings indicate that rmMeteorin has a robust and sustained antinociceptive effect in the paclitaxel-induced peripheral neuropathy model and the development of recombinant human Meteorin could be a novel and effective therapeutic for chemotherapy-induced peripheral neuropathy treatment. PERSPECTIVE: Chemotherapy neuropathy is a major clinical problem that decreases quality of life for cancer patients and survivors. Our experiments demonstrate that Meteorin treatment alleviates pain-related behaviors, and signs of neurotoxicity in a mouse model of paclitaxel neuropathy.

SDI-118, a novel procognitive SV2A modulator: First-in-human randomized controlled trial including PET/fMRI assessment of target engagement.

Background: Current treatments for progressive neurodegenerative disorders characterized by cognitive impairment either have limited efficacy or are lacking altogether. SDI-118 is a small molecule which modulates the activity of synaptic vesicle glycoprotein 2A (SV2A) in the brain and shows cognitive enhancing effects in a range of animal models of cognitive deficit. Methods: This first-in-human study evaluated safety, tolerability, and pharmacokinetics/pharmacodynamics of SDI-118 in single ascending oral doses up to 80 mg administered to 32 healthy male subjects. Brain target occupancy was measured in eight subjects using positron emission tomography with PET-ligand [11C]-UCB-J. Food effect was assessed in seven subjects. Mood state was regularly evaluated using standardized questionnaires, and resting state fMRI data were analyzed as exploratory objectives. Key Results: At all doses tested, SDI-118 was well tolerated and appeared safe. Adverse events were mainly dizziness, hypersomnia, and somnolence. All were mild in intensity and increased in frequency with increasing administered dose. No dose-limiting adverse reactions were observed at any dose. SDI-118 displayed a linear pharmacokinetic profile with no significant food effect. Brain penetration and target engagement were demonstrated by a dose-proportional SV2A occupancy. Conclusion: Single oral doses of SDI-118 up to 80 mg were very well tolerated in healthy male subjects. Dose-proportional SV2A occupancy in the brain was demonstrated with brain imaging. Adverse effects in humans mainly occurred in higher dose ranges, with high occupancy levels, and were all mild and self-limiting. These data support further clinical exploration of the compound in patients with cognitive disorders. Clinical Trial Registration: https://clinicaltrials.gov/, identifier NCT05486195.

Adult Neurogenesis and Antidepressant Treatment: The Surprise Finding by Ron Duman and the Field 20 Years Later.

Of Duman's many influential findings, the finding that long-term treatment with antidepressant drugs produces an increase in neurogenesis in the subgranular zone of the adult hippocampus may be one of the most enduring and far-reaching. This novel discovery and his decades of continued research in the field led to a new hypothesis about the mechanism of action of antidepressants, providing a critical step in our understanding of the neurotrophic hypothesis of depression and synaptic plasticity. It is now accepted that antidepressant treatments can oppose and even reverse the effects of stress on the brain and on newly born hippocampal cells, possibly via neurotrophic factors, which Duman had continued to explore. Furthermore, ablation studies have shown preclinically that hippocampal neurogenesis may be necessary for some of the clinical effects of antidepressant drugs. Duman's laboratory continued to interrogate neurotrophins and synaptic plasticity, demonstrating that newer clinically approved antidepressant compounds also affect neurogenesis and synaptic plasticity. In this review, we summarize Duman's original findings and discuss the current state of the field of neurogenesis with respect to animal models and human studies and the implications of those findings on the field of drug discovery.

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

BACKGROUND: Electroconvulsive 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. METHODS: ECS 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. RESULTS: A 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. CONCLUSION: A 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.

NMDAR activation regulates the daily rhythms of sleep and mood.

STUDY OBJECTIVES: The present studies examine the effects of NMDAR activation by NYX-2925 diurnal rhythmicity of both sleep and wake as well as emotion. METHODS: Twenty-four-hour sleep EEG recordings were obtained in sleep-deprived and non-sleep-deprived rats. In addition, the day-night cycle of both activity and mood was measured using home cage ultrasonic-vocalization recordings. RESULTS: NYX-2925 significantly facilitated non-REM (NREM) sleep during the lights-on (sleep) period, and this effect persisted for 3 days following a single dose in sleep-deprived rats. Sleep-bout duration and REM latencies were increased without affecting total REM sleep, suggesting better sleep quality. In addition, delta power during wake was decreased, suggesting less drowsiness. NYX-2925 also rescued learning and memory deficits induced by sleep deprivation, measured using an NMDAR-dependent learning task. Additionally, NYX-2925 increased positive affect and decreased negative affect, primarily by facilitating the transitions from sleep to rough-and-tumble play and back to sleep. In contrast to NYX-2925, the NMDAR antagonist ketamine acutely (1-4 hours post-dosing) suppressed REM and non-REM sleep, increased delta power during wake, and blunted the amplitude of the sleep-wake activity rhythm. DISCUSSION: These data suggest that NYX-2925 could enhance behavioral plasticity via improved sleep quality as well as vigilance during wake. As such, the facilitation of sleep by NYX-2925 has the potential to both reduce symptom burden on neurological and psychiatric disorders as well as serve as a biomarker for drug effects through restoration of sleep architecture.

NYX-2925, A Novel N-methyl-D-aspartate Receptor Modulator: A First-in-Human, Randomized, Double-blind Study of Safety and Pharmacokinetics in Adults.

NYX-2925, a new chemical entity, acts as a co-agonist to glutamate at the N-methyl-D-aspartate receptor (NMDAR). At low concentrations of endogenous agonists (glycine/D-serine), NYX-2925 partially activates NMDARs, modulating neural pathways relevant for chronic pain. NYX-2925 is being developed for the treatment of chronic pain conditions, including painful diabetic peripheral neuropathy and fibromyalgia. In this first-in-human, phase I, single-ascending dose (50-1,200 mg) and multiple-ascending dose (150-900 mg) study, the safety, tolerability, and pharmacokinetics (PKs) of NYX-2925 were evaluated in 84 healthy adult volunteers. No safety concerns emerged, including no dissociative side effects. NYX-2925 exhibited dose-proportional PKs and minimal accumulation following once-daily dosing for 7 days. Cerebrospinal fluid (CSF) measurements confirmed that NYX-2925 crosses the blood brain barrier, with maximum CSF concentrations approximating 6-9% of maximum plasma concentrations at the same dose level. NYX-2925 was safe and well-tolerated in healthy volunteers, and the study results support the continued clinical development for chronic pain conditions.

Mitochondria Are Critical for BDNF-Mediated Synaptic and Vascular Plasticity of Hippocampus following Repeated Electroconvulsive Seizures.

Background: Electroconvulsive therapy is a fast-acting and efficient treatment of depression used in the clinic. The underlying mechanism of its therapeutic effect is still unclear. However, recovery of synaptic connections and synaptic remodeling is thought to play a critical role for the clinical efficacy obtained from a rapid antidepressant response. Here, we investigated the relationship between synaptic changes and concomitant nonneuronal changes in microvasculature and mitochondria and its relationship to brain-derived neurotrophic factor level changes after repeated electroconvulsive seizures, an animal model of electroconvulsive therapy. Methods: Electroconvulsive seizures or sham treatment was given daily for 10 days to rats displaying a genetically driven phenotype modelling clinical depression: the Flinders Sensitive and Resistant Line rats. Stereological principles were employed to quantify numbers of synapses and mitochondria, and the length of microvessels in the hippocampus. The brain-derived neurotrophic factor protein levels were quantified with immunohistochemistry. Results: In untreated controls, a lower number of synapses and mitochondria was accompanied by shorter microvessels of the hippocampus in "depressive" phenotype (Flinders Sensitive Line) compared with the "nondepressed" phenotype (Flinders Resistant Line). Electroconvulsive seizure administration significantly increased the number of synapses and mitochondria, and length of microvessels both in Flinders Sensitive Line-electroconvulsive seizures and Flinders Resistant Line-electroconvulsive seizures rats. In addition, the amount of brain-derived neurotrophic factor protein was significantly increased in Flinders Sensitive Line and Flinders Resistant Line rats after electroconvulsive seizures. Furthermore, there was a significant positive correlation between brain-derived neurotrophic factor level and mitochondria/synapses. Conclusion: Our results indicate that rapid and efficient therapeutic effect of electroconvulsive seizures may be related to synaptic plasticity, accompanied by brain-derived neurotrophic factor protein level elevation and mitochondrial and vascular support.

NYX-2925 Is a Novel NMDA Receptor-Specific Spirocyclic-ß-Lactam That Modulates Synaptic Plasticity Processes Associated with Learning and Memory.

Background: N-methyl-D-aspartate receptors are one member of a family of ionotropic glutamate receptors that play a pivotal role in synaptic plasticity processes associated with learning and have become attractive therapeutic targets for diseases such as depression, anxiety, schizophrenia, and neuropathic pain. NYX-2925 ((2S, 3R)-3-hydroxy-2-((R)-5-isobutyryl-1-oxo-2,5-diazaspiro[3.4]octan-2-yl)butanamide) is one member of a spiro-ß-lactam-based chemical platform that mimics some of the dipyrrolidine structural features of rapastinel (formerly GLYX-13: threonine-proline-proline-threonine) and is distinct from known N-methyl-D-aspartate receptor agonists or antagonists such as D-cycloserine, ketamine, MK-801, kynurenic acid, or ifenprodil. Methods: The in vitro and in vivo pharmacological properties of NYX-2925 were examined. Results: NYX-2925 has a low potential for "off-target" activity, as it did not exhibit any significant affinity for a large panel of neuroactive receptors, including hERG receptors. NYX-2925 increased MK-801 binding to human N-methyl-D-aspartate receptor NR2A-D subtypes expressed in HEK cells and enhanced N-methyl-D-aspartate receptor current and long-term potentiation (LTP) in rat hippocampal slices (100-500 nM). Single dose ex vivo studies showed increased metaplasticity in a hippocampal LTP paradigm and structural plasticity 24 hours after administration (1 mg/kg p.o.). Significant learning enhancement in both novel object recognition and positive emotional learning paradigms were observed (0.01-1 mg/kg p.o.), and these effects were blocked by the N-methyl-D-aspartate receptor antagonist CPP. NYX-2925 does not show any addictive or sedative/ataxic side effects and has a therapeutic index of >1000. NYX-2925 (1 mg/kg p.o.) has a cerebrospinal fluid half-life of 1.2 hours with a Cmax of 44 nM at 1 hour. Conclusions: NYX-2925, like rapastinel, activates an NMDA receptor-mediated synaptic plasticity process and may have therapeutic potential for a variety of NMDA receptor-mediated central nervous system disorders.

Neurovascular plasticity of the hippocampus one week after a single dose of ketamine in genetic rat model of depression.

Glutamatergic system and the structural plasticity hypothesis are principal components for rapid and sustained antidepressant effects of novel antidepressant therapeutics. This study represents the first investigation of the structural plasticity of the hippocampus as one of the main contributed mechanisms to the sustained anti-depressive effect of ketamine. Flinders Sensitive Line (FSL) and Flinders Resistant Line (FRL) rats were given a single intraperitoneal injection of ketamine (15 mg/kg) or saline 7 days before perfusion-fixed. The optical fractionator method was used to estimate the total number of neurons in the granular cell layer. Microvessel length in the molecular layer of DG was evaluated with global spatial sampling method. By use of the physical disector method, the number of synapses was estimated. The volume of the hippocampus was larger in the FRL-vehicle rats compared with FSL-vehicle group and in FSL-ketamine versus FSL-vehicle rats (P < 0.05). The number of non-perforated synapses was significantly higher in the FSL-ketamine versus FSL-vehicle group, (P = 0.01). A significant effect of ketamine on enhancement of the number of neurons in DG in FSL rats was observed (P = 0.01). The total length of the microvessels 1 week after ketamine treatment in the FSL rats significantly increased (P < 0.05). Our results indicate that neurovascular changes of hippocampus could be one of the possible mechanisms underlying the sustained antidepressant effect of ketamine by reversing alteration of the number of the excitatory synapses, neuronal number and length of the microvessels in the hippocampus. © 2016 Wiley Periodicals, Inc.

Mitochondrial plasticity of the hippocampus in a genetic rat model of depression after antidepressant treatment.

Depressive disorders and the treatment thereof have been associated with a number of neuroplastic events, such as neurogenesis and synaptic remodeling in discrete areas of the brain. The associations of these events in changes regarding the energy supply have not been investigated. Here, we investigated the changes in mitochondrial plasticity and its correlation to morphological alterations of neuroplasticity in the hippocampus, both associated with a depressive phenotype, and after treatment, with antidepressant imipramine. Design-based stereological methods were used to estimate the number and volume of mitochondria in CA1 of the hippocampus in two different strains of rats, the Sprague-Dawley (SD) and Flinders rats, which display a genetic susceptibility to depressive behavior, the Flinders-sensitive line (FSL) and their corresponding controls, the Flinders-resistant line (FRL). Results showed a significantly reduced number of mitochondria in CA1, which was significantly smaller in the untreated FSL saline group compared to the FRL group. However, the mean volume of mitochondria was significantly larger in the FSL saline group compared to the FRL saline group. Following treatment, the FSL imipramine group showed a significant increase in the number of mitochondria compared to the FSL saline group. Treatment with imipramine in the SD rats did not induce significant differences in the number of mitochondria. Our results indicate that depression may be related to impairments of mitochondrial plasticity in the hippocampus and antidepressant treatment may counteract with the structural impairments. Moreover, the changes in mitochondrial morphology and number are a consistent feature of neuroplasticity.

Quantitative hippocampal structural changes following electroconvulsive seizure treatment in a rat model of depression.

OBJECTIVE: The pathophysiology of depression and the effects of antidepressant treatment are hypothesized to be related to hippocampal structural changes. This study aims to investigate the effect of electroconvulsive seizures on behavior and hippocampal structure in a rat model of depression. METHODS: Flinders Sensitive Line (FSL) and Flinders Resistant Line (FRL) rats were treated daily for 10 days with either electroconvulsive seizures or sham treatment. The behavior was evaluated using the forced swim test. Design-based stereological methods were used to quantify the hippocampal volume and the numbers of neurons and glial cells in specific hippocampal subregions. RESULTS: The basal level of hippocampal volume and neuron number differed significantly between the two rat strains, and a trend toward the FSL strain having more glial cells was found. The structural differences found between the sham-treated animals were counteracted by electroconvulsive seizure (ECS) treatment, which also normalized the behavior. ECS treatment increased the number of glial cells in hilus significantly in the FRL rats and with the same tendency for the FSL rats. CONCLUSION: Our results indicate that along with hippocampal neurogenesis, gliogenesis may also be involved in the pathophysiology of depression and in the effect of antidepressant treatment. The underlying mechanisms remain unknown, and further investigations are required to clarify whether the structural changes are necessary to induce a therapeutic effect of antidepressant treatment or if they rather represent an epiphenomenon.

Imipramine treatment increases the number of hippocampal synapses and neurons in a genetic animal model of depression.

The aim was to investigate treatment effects of the antidepressant imipramine on the markers of neuronal plasticity. We investigated changes in neuron and synapse numbers in a rat strain that displays a genetic susceptibility to depressive behavior, the Flinders Sensitive and Resistant Lines (FSL/FRL). All rats were treated with imipramine (15 mg/kg) or saline (i.p) once daily for 25 days. The volume, neuron and synapse numbers in the hippocampus were estimated using design-based stereological methods. Under untreated conditions, the volume and the number of neurons and synapses were significantly smaller in the FSL saline group (untreated "depressed" rats) compared with the FRL saline group (normal rats), showing correlation to the observed decreased immobility in the forced swim test. Imipramine treatment significantly increased the number of neurons in the granule cell layer (GCL) and spine synapses in the CA1 in the FSL imipramine group (treated "depressed" rats) compared with the FSL saline group. The neuron numbers in the GCL and Hilus showed no differences in the FSL imipramine group compared to the FRL saline group. In conclusion, baseline levels of the volume and the number of neurons and spine synapses in hippocampus were significantly smaller in the untreated FSL rats. Our findings indicate that chronic imipramine treatment reverses the suppression of neurogenesis and synaptogenesis in the hippocampus of the "depressed" FSL rats, and this occurs in correlation with behavioral effects. Our results support the neuronal plasticity hypothesis that depressive disorders may be related to impairments of structural plasticity and neuronal viability in hippocampus, furthermore, antidepressant treatment counteracts the structural impairments.

Repeated electroconvulsive seizures increase the total number of synapses in adult male rat hippocampus.

The underlying mechanism of the therapeutic effect of electroconvulsive therapy (ECT) is still unclear. Here we investigated whether repeated electroconvulsive seizures (ECS), an animal model of ECT, in rats induce neuroplastic changes in the subregions of the hippocampus. ECS or sham treatment was given daily for 10 days to adult male rats. Stereological principles were employed to quantify volumes and the number of neurons and synapses. Volumes of granule cell layer (GCL) and Hilus in Dentate Gyrus of the hippocampus were significantly larger in the ECS treatment group. The neuron numbers in GCL, synapse numbers (including total synapses, spine synapses, and both perforated and nonperforated spine synapse subtypes) and synapse height in CA1 were significantly increased in the ECS treatment group. Our results indicated that repeated ECS induces neurogenesis, synaptogenesis and remodelling of synapses in rat hippocampus. This could provide a potential mechanism to explain the therapeutic effect of ECS.

Electroconvulsive seizure restores neurogenesis and hippocampus-dependent fear memory after disruption by irradiation.

Ongoing neurogenesis in the adult hippocampus is thought to play a role in learning and memory processes, and in response to antidepressant treatments. Low doses of irradiation (IRR) produce a significant long-lasting inhibitory effect on hippocampal neurogenesis that correlates with long-lasting behavioral deficits. Here we report that electroconvulsive seizure (ECS), which robustly increases adult neurogenesis in naïve animals, also reverses the disruption of neurogenesis produced by IRR exposure. Moreover, we find that vascular endothelial growth factor (VEGF) is an essential mediator of this effect. Expression of VEGF in the granule cell layer (GCL) of the hippocampus is decreased by IRR, and ECS administration reverses this deficit in VEGF. There is a corresponding alteration in the number of endothelial cells, which express VEGF, in the hippocampal GCL following IRR and ECS. We also find that blockade of VEGF signaling attenuates ECS-induced proliferation, and VEGF infusion partially restores proliferation in irradiated animals. To examine the functional consequences of IRR and ECS on neurogenesis, hippocampus-dependent contextual fear conditioning was assessed. We found that following disruption by IRR, ECS restores contextual learning to baseline levels at time points consistent with its effects on neurogenesis. These findings demonstrate that ECS, in part via induction of VEGF, can reverse long-term neurogenesis deficits resulting from IRR, and that these effects have functional consequences on hippocampus-dependent fear memory.

Changes in rat hippocampal CA1 synapses following imipramine treatment.

Neuronal plasticity in hippocampus is hypothesized to play an important role in both the pathophysiology of depressive disorders and the treatment. In this study, we investigated the consequences of imipramine treatment on neuroplasticity (including neurogenesis, synaptogenesis, and remodelling of synapses) in subregions of the hippocampus by quantifying number of neurons and synapses. Adult male Sprague-Dawley rats were injected with imipramine or saline (i.p.) daily for 14 days. Unbiased stereological methods were used to quantify the number of neurons and synapses. No differences in the volume and number of neurons of hippocampal subregions following imipramine treatment were found. However, the number and percentage of CA1 asymmetric spine synapses increased significantly and, conversely, the percentage of asymmetric shaft synapses significantly decreased in the imipramine treated group. Our results indicate that administration of imipramine for 14 days in normal rats could significantly increase the excitatory spine synapses, and change the relative distribution of spine and shaft synapses. We speculate that the present findings may be explained by the establishment of new synaptic connections and by remodelling or transformation of existing synapses.

Differential regulation of c-Fos and FosB in the rat brain after amygdala kindling.

Members of the inducible transcription factor Fos family, that are part of the AP-1 complex that binds to the corresponding promoter site, are implicated in the regulation of gene transcription after acute and chronic seizures. However, little is known about the temporal expression of the AP-1 transcription factors and if individual proteins composing this complex have distinct roles in development and maintenance of permanent epilepsy. In this study, the AP-1 binding capacity, its content of different Fos proteins, and the anatomical specificity, were analyzed 2 or 18 h after achieving full kindling in rats. The same analysis was performed in fully kindled animal receiving a new stimulus after a 3-week pause to determine the extent of stability of the AP-1 transcription factors. While both c-Fos and FosB were induced in all cortical areas after a single stimulus, only FosB-immunoreactivity remained after 18 h. A single stimulation to kindled animals left undisturbed for 3 weeks induced a long-lasting upregulation of AP-1 binding in the frontal cortex, but not in the hippocampus suggesting a permanent exposure of AP-1 heterocomplexes in the frontal cortex. Supershift assays showed that FosB is the dominant component of the long-term AP-1 complex. It is concluded that the AP-1 binding complex in fully kindled rats is composed of different proteins, and that FosB-containing AP-1 complexes mediate long-term effects in the frontal cortex.

Electroconvulsive seizure treatment increases cell proliferation in rat frontal cortex.

Recent studies have demonstrated increased neurogenesis in adult hippocampus in response to electroconvulsive seizure (ECS) or antidepressant drug treatment. Adult neurogenesis in the subgranular zone of the hippocampus and the subventricular zone is well established, whereas neuronal proliferation outside of these areas under unstimulated conditions is not observed. Since mood disorders are likely to involve brain regions in addition to hippocampus, particularly the frontal cortex, it is likely that antidepressant treatments produce cellular changes in these brain regions as well. In this study, we have investigated the effect of repeated ECS administration on the proliferation of cells in the frontal cortex, and we have examined the phenotype of these cells 4 weeks after labeling with a cell division marker. We found that ECS treatment increases the number of newly divided cells in the frontal cortex and that these new cells express markers of either endothelial cells or oligodendrocytes, but not neurons. It is possible that increased proliferation of these cell types in the frontal cortex could reverse the loss of glial cell number and the reduced volume that has been reported in the frontal cortex of depressed patients.

Day-night changes in downstream regulatory element antagonist modulator/potassium channel interacting protein activity contribute to circadian gene expression in pineal gland.

The molecular mechanisms controlling the oscillatory synthesis of melatonin in rat pineal gland involve the rhythmic expression of several genes including arylalkylamine N-acetyltransferase (AA-NAT), inducible cAMP early repressor (ICER), and Fos-related antigen-2 (fra-2). Here we show that the calcium sensors downstream regulatory element antagonist modulator/potassium channel interacting protein (DREAM/KChIP)-3 and KChIP-1, -2 and -4 bind to downstream regulatory element (DRE) sites located in the regulatory regions of these genes and repress basal and induced transcription from ICER, fra-2 or AA-NAT promoters. Importantly, we demonstrate that the endogenous binding activity to DRE sites shows day-night oscillations in rat pineal gland and retina but not in the cerebellum. The peak of DRE binding activity occurs during the day period of the circadian cycle, coinciding with the lowest levels of fra-2, ICER, and AA-NAT transcripts. We show that a rapid clearance of DRE binding activity during the entry in the night period is related to changes at the posttranscriptional level of DREAM/KChIP. The circadian pattern of DREAM/KChIP activity is maintained under constant darkness, indicating that an endogenous clock controls DREAM/KChIP function. Our data suggest involvement of the family of DREAM repressors in the regulation of rhythmically expressed genes engaged in circadian rhythms.

Downregulation of the CCAAT-enhancer binding protein beta in deltaFosB transgenic mice and by electroconvulsive seizures.

Previous studies demonstrate that chronic, but not acute electroconvulsive seizures (ECS), increases levels of deltaFosB, a long-lasting transcription factor, in the hippocampus, and this effect correlates with the slow onset and long-lasting clinical effects of antidepressant treatment. To understand how deltaFosB mediates long-term plasticity in the hippocampus, we analyzed the gene expression profile of inducible transgenic mice expressing deltaFosB with a highly sensitive microarray assay and a customized computer analysis program. The CCAAT-enhancing binding protein-beta (C/EBPbeta) was identified as one of the genes downregulated by deltaFosB in the hippocampus. The downregulation of C/EBPbeta in the inducible deltaFosB transgenic mice was confirmed by other quantitative assays including real-time RT-PCR and low density dot blotting. Analysis of the C/EBPbeta expression in the hippocampus of rats treated with ECS revealed that the C/EBPbeta mRNA was also downregulated by chronic, but not acute ECS administration, the most effective treatment for depression. Given the reported role of C/EBPbeta in behavioral conditioning models, it is possible that the deltaFosB-mediated downregulation of C/EBPbeta in the hippocampus may be a molecular mechanism by which antidepressants alleviate some of the symptoms of depressed patients.

Chronic electroconvulsive seizure up-regulates beta-catenin expression in rat hippocampus: role in adult neurogenesis.

BACKGROUND: Beta-catenin was discovered as a cytoskeletal protein, constituting a link between the cadherins to the actin cytoskeleton. Aside from this function, beta-catenin is a key effector molecule in the Wnt signaling pathway, serving as a downstream transcription factor. METHODS: In this study, we examined the influence of electroconvulsive seizures (ECS) on the expression of beta-catenin, as well as expression of Wnt-2, in rat hippocampus. Repeated administration of generalized seizures increased levels of beta-catenin immunoreactivity in the subgranular zone of the hippocampus. To assess the relationship of beta-catenin to cell division in the dentate gyrus of the adult rat hippocampus, colocalization of beta-catenin with a marker of cell division was examined. RESULTS: Beta-catenin immunoreactivity was consistently localized in newborn cells in this region, indicating a possible role in cell division and differentiation in adult hippocampus. We also found that ECS treatment significantly increased levels of Wnt-2, one of the ligands that activates beta-catenin signaling. CONCLUSIONS: These results demonstrate that ECS increases Wnt-beta-catenin signaling and suggest that this pathway could mediate in part the neuronal adaptations underlying the therapeutic action of this treatment paradigm.