Physiological mechanism of strigolactone enhancing tolerance to low light stress in cucumber seedlings.

Strigolactone is a newly discovered type of plant hormone that has multiple roles in modulating plant responses to abiotic stress. Herein, we aimed to investigate the effects of exogenous GR24 (a synthetic analogue of strigolactone) on plant growth, photosynthetic characteristics, carbohydrate levels, endogenous strigolactone content and antioxidant metabolism in cucumber seedlings under low light stress. The results showed that the application of 10 µM GR24 can increase the photosynthetic efficiency and plant biomass of low light-stressed cucumber seedlings. GR24 increased the accumulation of carbohydrates and the synthesis of sucrose-related enzyme activities, enhanced antioxidant enzyme activities and antioxidant substance contents, and reduced the levels of H2O2 and MDA in cucumber seedlings under low light stress. These results indicate that exogenous GR24 might alleviate low light stress-induced growth inhibition by regulating the assimilation of carbon and antioxidants and endogenous strigolactone contents, thereby enhancing the tolerance of cucumber seedlings to low light stress.

Agomelatine protects against neuronal damage without preventing epileptogenesis in the kainate model of temporal lobe epilepsy.

Recent studies about the novel antidepressant agomelatine, which is a mixed MT1 and MT2 melatonin receptor agonist and 5HT2C serotonin receptor antagonist possessing an anticonvulsant and neuroprotective action, suggest that it may have potential to contribute against epileptogenesis and epilepsy-induced memory impairment. In order to ascertain whether protection of some brain structures could suppress epileptogenesis, in the present study, we evaluated the effect of chronic post-status treatment with agomelatine on epileptogenesis, behavioral and neuronal damage induced by kainate acid (KA) status epilepticus (SE). Agomelatine/vehicle treatment (40mg/kg, i.p.) started one hour after SE and continued up to 10weeks in Wistar rats. Latency for onset of spontaneous motor seizures (SMS) and their frequency was detected by a 24-h video-recording. Locomotor activity, anxiety and hippocampus-dependent spatial memory in open field (OF), elevated plus maze (EPM), light-dark test (LDT) and radial arm maze (RAM) test, respectively, were evaluated during the last two weeks after SE. Agomelatine significantly decreased the latency for onset of SMS and increased the seizure frequency during the 2nd and the 3rd week of treatment. The MT1 and MT2 receptor agonist and serotonin 5HT2C receptor antagonist exacerbated the KA-induced hyperlocomotion and impulsive behavior and it was unable to prevent spatial memory impairment of epileptic rats. However, agomelatine induced a neuroprotection in the dorsal hippocampus, specifically in the CA1, septal CA2 and partially in the CA3c region, the hilus of the dentate gyrus, piriform cortex and septo-temporal and temporal basolateral amygdala. Our findings suggest that the beneficial impact against SE-induced neuronal loss exerted by agomelatine is not crucial for the suppression of epileptogenesis and its deleterious consequences in KA model of temporal lobe epilepsy.

Meclofenamic acid improves the signal to noise ratio for visual responses produced by ectopic expression of human rod opsin.

PURPOSE: Retinal dystrophy through outer photoreceptor cell death affects 1 in 2,500 people worldwide with severe impairment of vision in advanced stages of the disease. Optogenetic strategies to restore visual function to animal models of retinal degeneration by introducing photopigments to neurons spared degeneration in the inner retina have been explored, with variable degrees of success. It has recently been shown that the non-steroidal anti-inflammatory and non-selective gap-junction blocker meclofenamic acid (MFA) can enhance the visual responses produced by an optogenetic actuator (channelrhodopsin) expressed in retinal ganglion cells (RGCs) in the degenerate retina. Here, we set out to determine whether MFA could also enhance photoreception by another optogenetic strategy in which ectopic human rod opsin is expressed in ON bipolar cells. METHODS: We used in vitro multielectrode array (MEA) recordings to characterize the light responses of RGCs in the rd1 mouse model of advanced retinal degeneration following intravitreal injection of an adenoassociated virus (AAV2) driving the expression of human rod opsin under a minimal grm6 promoter active in ON bipolar cells. RESULTS: We found treated retinas were light responsive over five decades of irradiance (from 1011 to 1015 photons/cm2/s) with individual RGCs covering up to four decades. Application of MFA reduced the spontaneous firing rate of the visually responsive neurons under light- and dark-adapted conditions. The change in the firing rate produced by the 2 s light pulses was increased across all intensities following MFA treatment, and there was a concomitant increase in the signal to noise ratio for the visual response. Restored light responses were abolished by agents inhibiting glutamatergic or gamma-aminobutyric acid (GABA)ergic signaling in the MFA-treated preparation. CONCLUSIONS: These results confirm the potential of MFA to inhibit spontaneous activity and enhance the signal to noise ratio of visual responses in optogenetic therapies to restore sight.

Daytime spikes in dopaminergic activity drive rapid mood-cycling in mice.

Disruptions in circadian rhythms and dopaminergic activity are involved in the pathophysiology of bipolar disorder, though their interaction remains unclear. Moreover, a lack of animal models that display spontaneous cycling between mood states has hindered our mechanistic understanding of mood switching. Here, we find that mice with a mutation in the circadian Clock gene (ClockΔ19) exhibit rapid mood-cycling, with a profound manic-like phenotype emerging during the day following a period of euthymia at night. Mood-cycling coincides with abnormal daytime spikes in ventral tegmental area (VTA) dopaminergic activity, tyrosine hydroxylase (TH) levels and dopamine synthesis. To determine the significance of daytime increases in VTA dopamine activity to manic behaviors, we developed a novel optogenetic stimulation paradigm that produces a sustained increase in dopamine neuronal activity and find that this induces a manic-like behavioral state. Time-dependent dampening of TH activity during the day reverses manic-related behaviors in ClockΔ19 mice. Finally, we show that CLOCK acts as a negative regulator of TH transcription, revealing a novel molecular mechanism underlying cyclic changes in mood-related behavior. Taken together, these studies have identified a mechanistic connection between circadian gene disruption and the precipitation of manic episodes in bipolar disorder.

[Foveolar effects of dexamethasone intravitreal implant in central retinal vein occlusion].

AIM: To evaluate functional and morphometric parameters of the central retina in patients with postocclusive macular edema treated with dexamethasone intravitreal implant injection. MATERIAL AND METHODS: We examined 5 patients (5 eyes) with newly diagnosed central retinal vein occlusion complicated by macular edema, including 4 men and 1 woman aged 55.8±3.65 years (experimental group). All the patients received a single injection of dexamethasone intravitreal implant. The maximum follow-up period was 12 months. The control group consisted of 5 presbiopic patients (10 eyes) aged 59.14±3.14 years. RESULTS: One month after injection, the best corrected visual acuity (BCVA) and central retinal light sensitivity improved (from 0.09±0.03 to 0.19±0.05 and from 3.18±0.19 to 11.07±0.97 dB, correspondingly), while foveolar thickness decreased from 425.36±57.87 to 273.75±36.65 µm. One year after the treatment, BCVA remained high and averaged 0.21±0.14. The total light sensitivity also remained higher than that at baseline, however, decreased down to 4.8±0.76 dB. Optical coherence tomography showed some flatness of the fovea. Foveolar thickness appeared 1.5 times higher than that in the control group and 1.2 times higher than that at the 1-month follow-up after dexamethasone intravitreal implant injection. Over the whole follow-up period, IOP has never significantly exceeded the baseline, optical media remained clear. CONCLUSION: 1. Dexamethasone intravitreal implant has been shown effective in resolving postocclusive macular edema, improving visual functions, and increasing central retinal light sensitivity within the first month after injection. 2. Positive changes in morphometric parameters of the central retina induced by the injection involve inner segments of photoreceptors as well as the outer nuclear, outer plexiform and inner nuclear layers. The morphofunctional effect persists for no less than 12 months after injection. 3. Over the 1-year follow-up period, there has been no negative influence of the implant on either intraocular pressure level, or lens transparency.

[Centrally acting cholinomimetics in the complex therapy of progressive glaucomatous optic neuropathy].

UNLABELLED: Many factors exist that are associated with higher risk of glaucoma progression. Arterial hypotension, low perfusion pressure, vasospastic syndrome, diabetes mellitus, myopia, etc. increase the need for neuroprotective therapy, which is aimed at stabilizing the pathological process and creating favorable conditions for maintaining visual functions. The aim of this study was to assess the therapeutic efficacy of Gliatilin as part of the complex treatment of progressive glaucomatous optic neuropathy. MATERIAL AND METHODS: A total of 240 patients were randomly selected and divided into 2 groups, 120 patients each. Both groups were matched for age, somatic comorbidity, and the gravity of the glaucomatous process. Patient age averaged 71.3±1.6 years. Advanced glaucoma prevailed in both groups: 70.0 and 76.6% correspondingly. Neuroprotective therapy included drugs from different pharmacological classes so that different aspects of pathogenesis were addressed. Apart from that, patients from Group I first received intravenous Gliatilin (1000 mg/4ml, 12--15 doses) and then switched to oral (1 capsule b.i.d. for 4 months). All patients underwent standard ophthalmic examination and static perimetry. RESULTS: No adverse effects were observed over the first two weeks of Gliatilin course, during which the patients stayed in the hospital. IOP level was normal and stable. Although neuroprotective therapy does not directly affect IOP, stability of the latter describes the dynamics of the glaucomatous process. When assessing changes in visual functions, particular attention was paid to the central visual field, foveolar and total light sensitivity, peripheral visual field, and MD and PSD indices. All mean values showed a tendency toward improvement, more pronounced in the Gliatilin group. CONCLUSION: A complex therapy cannot be limited to a single drug only, and to make better decisions, one should consider not only ocular, but also general condition of the patient. Adjuvant Gliatilin in the complex therapy of progressive glaucoma is appropriate and efficient, especially in case of systemic atherosclerosis and cerebrovascular insufficiency. The frequency of stabilization therapy depends on the efficacy of the latest course and clinical manifestations of the glaucomatous process.

Inhibition of Acid Sphingomyelinase by Antidepressants Counteracts Stress-Induced Activation of P38-Kinase in Major Depression.

BACKGROUND/AIMS: Major depressive disorder is a common disease with serious morbidity, including increased risk of death from suicide. Major depressive disorder is treated with antidepressants. However, the molecular targets of antidepressants remained ill-defined and require further elucidation. METHODS: Mice were treated with corticosterone to induce stress, amitriptyline and the p38-kinase (p38K) inhibitor SB239063 or a combination of these drugs. Phosphorylation of p38K in hippocampal neurons was determined by immunostaining with a phospho-specific antibody, neuronal proliferation using BrdU-labelling and behaviour employing a set of behavioural tests. RESULTS: Corticosterone induced phosphorylation/activation of p38K in the hippocampus in vivo. Antidepressants reversed the effect of corticosterone on p38K activation in wildtype mice, but had no effect in acid sphingomyelinase-deficient animals. Corticosterone also reduced neurogenesis and triggered depression-like behavioural changes, effects that were prevented by pharmacological inhibition of p38K. CONCLUSION: Stress induces p38K phosphorylation/activation in the hippocampus and thereby reduces neurogenesis and induces depression-like symptoms, events that are prevented by antidepressants via inhibition of the acid sphingomyelinase/ceramide system.

Regulation of photoreceptor gap junction phosphorylation by adenosine in zebrafish retina.

Electrical coupling of photoreceptors through gap junctions suppresses voltage noise, routes rod signals into cone pathways, expands the dynamic range of rod photoreceptors in high scotopic and mesopic illumination, and improves detection of contrast and small stimuli. In essentially all vertebrates, connexin 35/36 (gene homologs Cx36 in mammals, Cx35 in other vertebrates) is the major gap junction protein observed in photoreceptors, mediating rod-cone, cone-cone, and possibly rod-rod communication. Photoreceptor coupling is dynamically controlled by the day/night cycle and light/dark adaptation, and is directly correlated with phosphorylation of Cx35/36 at two sites, serine110 and serine 276/293 (homologous sites in teleost fish and mammals, respectively). Activity of protein kinase A (PKA) plays a key role during this process. Previous studies have shown that activation of dopamine D4 receptors on photoreceptors inhibits adenylyl cyclase, down-regulates cAMP and PKA activity, and leads to photoreceptor uncoupling, imposing the daytime/light condition. In this study, we explored the role of adenosine, a nighttime signal with a high extracellular concentration at night and a low concentration in the day, in regulating photoreceptor coupling by examining photoreceptor Cx35 phosphorylation in zebrafish retina. Adenosine enhanced photoreceptor Cx35 phosphorylation in daytime, but with a complex dose-response curve. Selective pharmacological manipulations revealed that adenosine A2a receptors provide a potent positive drive to phosphorylate photoreceptor Cx35 under the influence of endogenous adenosine at night. A2a receptors can be activated in the daytime as well by micromolar exogenous adenosine. However, the higher affinity adenosine A1 receptors are also present and have an antagonistic though less potent effect. Thus, the nighttime/darkness signal adenosine provides a net positive drive on Cx35 phosphorylation at night, working in opposition to dopamine to regulate photoreceptor coupling via a push-pull mechanism. However, the lower concentration of adenosine present in the daytime actually reinforces the dopamine signal through action on the A1 receptor.

Dopamine modulates the off pathway in light-adapted mouse retina.

DL-2-Amino-4-phosphonobutyric acid (APB) is often used as a tool to block On pathways in studies of interactions between On and Off pathways in retinas. APB is an agonist of mGluR6 receptors and hyperpolarizes the On cone bipolar cells and rod bipolar cells. How APB affects Off responses of retinal ganglion cells (RGCs) in mouse retinas under dark and light adaptation is not clear. The light-evoked excitatory postsynaptic currents (light-evoked EPSCs) from Off and On-Off RGCs cells were recorded using whole-cell patch-clamp recording to assess how APB affects Off responses (light-evoked Off EPSCs) of RGCs in dark- and light-adapted mouse retinas. We found that APB differentially affected Off responses of RGCs in dark- and light-adapted mouse retinas. Under dark adaptation, while the APB-sensitive Off responses were blocked, APB increased the remaining Off responses (mainly from the secondary rod Off pathways) via removal of inhibition from On pathways to Off pathways. Under light adaptation, APB decreased Off responses. Glycinergic and GABAergic antagonists did not prevent the APB-induced reduction of Off responses of RGCs; however, a dopaminergic type 1 receptor (D(1)) blocker (SCH 23390) and a hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker (ZD 7288) prevented the APB-induced reduction of Off responses of RGCs under light adaptation. The results indicated afunctional circuit: On cone bipolar cells to Off cone bipolar cells via D(1) receptors and HCN channels.

The modulatory role of taurine in retinal ganglion cells.

Taurine (2-aminoethylsuphonic acid) is present in nearly all animal tissues, and is the most abundant free amino acid in muscle, heart, CNS, and retina. Although it is known to be a major cytoprotectant and essential for normal retinal development, its role in retinal neurotransmission and modulation is not well understood. We investigated the response of taurine in retinal ganglion cells, and its effect on synaptic transmission between ganglion cells and their presynaptic neurons. We find that taurine-elicited currents in ganglion cells could be fully blocked by both strychnine and SR95531, glycine and GABA(A) receptor antagonists, respectively. This suggests that taurine-activated receptors might share the antagonists with GABA and glycine receptors. The effect of taurine at micromolar concentrations can effectively suppress spontaneous vesicle release from the presynaptic neurons, but had limited effects on light-evoked synaptic signals in ganglion cells. We also describe a metabotropic effect of taurine in the suppression of light-evoked response in ganglion cells. Clearly, taurine acts in multiple ways to modulate synaptic signals in retinal output neurons, ganglion cells.

Role of cerebellar cortical protein synthesis in transfer of memory trace of cerebellum-dependent motor learning.

We developed a new protocol that induces long-term adaptation of horizontal optokinetic response (HOKR) eye movement by hours of spaced training and examined the role of protein synthesis in the cerebellar cortex in the formation of memory of adaptation. Mice were trained to view 800 cycles of screen oscillation either by 1 h of massed training or by 2.5 h to 8 d of training with 0.5 h to 1 d space intervals. The HOKR gains increased similarly by 20-30% at the end of training; however, the gains increased by 1 h of massed training recovered within 24 h, whereas the gains increased by spaced training were sustained over 24 h. Bilateral floccular lidocaine microinfusions immediately after the end of training recovered the gains increased by 1 h of massed training but did not affect the gains increased by 4 h of spaced training, suggesting that the memory trace of adaptation was transferred from the flocculus to the vestibular nuclei within 4 h of spaced training. Blockade of floccular protein synthesis, examined by bilateral floccular microinfusions of anisomycin or actinomycin D 1-4 h before the training, impaired the gains increased by 4 h of spaced training but did not affect the gains increased by 1 h of massed training. These findings suggest that the transfer of the memory trace of adaptation occurs within 4 h of spaced training, and proteins synthesized in the flocculus during training period may play an important role in memory transfer.

Bcl-xL-mediated remodeling of rod and cone synaptic mitochondria after postnatal lead exposure: electron microscopy, tomography and oxygen consumption.

PURPOSE: Postnatal lead exposure produces rod-selective and Bax-mediated apoptosis, decreased scotopic electroretinograms (ERGs), and scotopic and mesopic vision deficits in humans and/or experimental animals. Rod, but not cone, inner segment mitochondria were considered the primary site of action. However, photoreceptor synaptic mitochondria were not examined. Thus, our experiments investigated the structural and functional effects of environmentally relevant postnatal lead exposure on rod spherule and cone pedicle mitochondria and whether Bcl-xL overexpression provided neuroprotection. METHODS: C57BL/6N mice pups were exposed to lead only during lactation via dams drinking water containing lead acetate. The blood [Pb] at weaning was 20.6±4.7 µg/dl, which decreased to the control value by 2 months. To assess synaptic mitochondrial structural differences and vulnerability to lead exposure, wild-type and transgenic mice overexpressing Bcl-xL in photoreceptors were used. Electron microscopy, three-dimensional electron tomography, and retinal and photoreceptor synaptic terminal oxygen consumption (QO(2)) studies were conducted in adult control, Bcl-xL, lead, and Bcl-xL/lead mice. RESULTS: The spherule and pedicle mitochondria in lead-treated mice were swollen, and the cristae structure was markedly changed. In the lead-treated mice, the mitochondrial cristae surface area and volume (abundance: measure correlated with ATP (ATP) synthesis) were decreased in the spherules and increased in the pedicles. Pedicles also had an increased number of crista segments per volume. In the lead-treated mice, the number of segments/crista and fraction of cristae with multiple segments (branching) similarly increased in spherule and pedicle mitochondria. Lead-induced remodeling of spherule mitochondria produced smaller cristae with more branching, whereas pedicle mitochondria had larger cristae with more branching and increased crista junction (CJ) diameter. Lead decreased dark- and light-adapted photoreceptor and dark-adapted photoreceptor synaptic terminal QO(2). Bcl-xL partially blocked many of the lead-induced alterations relative to controls. However, spherules still had partially decreased abundance, whereas pedicles still had increased branching, increased crista segments per volume, and increased crista junction diameter. Moreover, photoreceptor and synaptic QO(2) were only partially recovered. CONCLUSIONS: These findings reveal cellular and compartmental specific differences in the structure and vulnerability of rod and cone inner segment and synaptic mitochondria to postnatal lead exposure. Spherule and pedicle mitochondria in lead-exposed mice displayed complex and distinguishing patterns of cristae and matrix damage and remodeling consistent with studies showing that synaptic mitochondria are more sensitive to Ca(2+) overload, oxidative stress, and ATP loss than non-synaptic mitochondria. The lead-induced decreases in QO(2) likely resulted from the decreased spherule cristae abundance and smaller cristae, perhaps due to Bax-mediated effects as they occurred in apoptotic rod inner segments. The increase in pedicle cristae abundance and CJ diameter could have resulted from increased Drp1-mediated fission, as small mitochondrial fragments were observed. The mechanisms of Bcl-xL-mediated remodeling might occur via interaction with formation of CJ protein 1 (Fcj1), whereas the partial protection of synaptic QO(2) might result from the enhanced efficiency of energy metabolism via Bcl-xL's direct interaction with the F1F0 ATP synthase and/or regulation of cellular redox status. These lead-induced alterations in photoreceptor synaptic terminal mitochondria likely underlie the persistent scotopic and mesopic deficits in lead-exposed children, workers, and experimental animals. Our findings stress the clinical and scientific importance of examining synaptic dysfunction following injury or disease during development, and developing therapeutic treatments that prevent synaptic degeneration in retinal and neurodegenerative disorders even when apoptosis is blocked.

Early retinoic acid deprivation in developing zebrafish results in microphthalmia.

Vitamin A deficiency causes impaired vision and blindness in millions of children around the world. Previous studies in zebrafish have demonstrated that retinoic acid (RA), the acid form of vitamin A, plays a vital role in early eye development. The objective of this study was to describe the effects of early RA deficiency by treating zebrafish with diethylaminobenzaldehyde (DEAB), a potent inhibitor of the enzyme retinaldehyde dehydrogenase (RALDH) that converts retinal to RA. Zebrafish embryos were treated for 2 h beginning at 9 h postfertilization. Gross morphology and retinal development were examined at regular intervals for 5 days after treatment. The optokinetic reflex (OKR) test, visual background adaptation (VBA) test, and the electroretinogram (ERG) were performed to assess visual function and behavior. Early treatment of zebrafish embryos with 100 µM DEAB (9 h) resulted in reduced eye size, and this microphthalmia persisted through larval development. Retinal histology revealed that DEAB eyes had significant developmental abnormalities but had relatively normal retinal lamination by 5.5 days postfertilization. However, the fish showed neither an OKR nor a VBA response. Further, the retina did not respond to light as measured by the ERG. We conclude that early deficiency of RA during eye development causes microphthalmia as well as other visual defects, and that timing of the RA deficiency is critical to the developmental outcome.

Transient early-life forebrain corticotropin-releasing hormone elevation causes long-lasting anxiogenic and despair-like changes in mice.

During development, early-life stress, such as abuse or trauma, induces long-lasting changes that are linked to adult anxiety and depressive behavior. It has been postulated that altered expression of corticotropin-releasing hormone (CRH) can at least partially account for the various effects of stress on behavior. In accord with this hypothesis, evidence from pharmacological and genetic studies has indicated the capacity of differing levels of CRH activity in different brain areas to produce behavioral changes. Furthermore, stress during early life or adulthood causes an increase in CRH release in a variety of neural sites. To evaluate the temporal and spatial specificity of the effect of early-life CRH exposure on adult behavior, the tetracycline-off system was used to produce mice with forebrain-restricted inducible expression of CRH. After transient elevation of CRH during development only, behavioral testing in adult mice revealed a persistent anxiogenic and despair-like phenotype. These behavioral changes were not associated with alterations in adult circadian or stress-induced corticosterone release but were associated with changes in CRH receptor type 1 expression. Furthermore, the despair-like changes were normalized with antidepressant treatment. Overall, these studies suggest that forebrain-restricted CRH signaling during development can permanently alter stress adaptation leading to increases in maladaptive behavior in adulthood.

Cannabinoids excite circadian clock neurons.

Cannabinoids, the primary active agent in drugs of abuse such as marijuana and hashish, tend to generate a distorted sense of time. Here we study the effect of cannabinoids on the brain's circadian clock, the suprachiasmatic nucleus (SCN), using patch clamp and cell-attached electrophysiological recordings, RT-PCR, immunocytochemistry, and behavioral analysis. The SCN showed strong expression of the cannabinoid receptor CB1R, as detected with RT-PCR. SCN neurons, including those using GABA as a transmitter, and axons within the SCN, expressed CB1R immunoreactivity. Behaviorally, cannabinoids did not alter the endogenous free-running circadian rhythm in the mouse brain, but did attenuate the ability of the circadian clock to entrain to light zeitgebers. In the absence of light, infusion of the CB1R antagonist AM251 caused a modest phase shift, suggesting endocannabinoid modulation of clock timing. Interestingly, cannabinoids had no effect on glutamate release from the retinohypothalamic projection, suggesting a direct action of cannabinoids on the retinohypothalamic tract was unlikely to explain the inhibition of the phase shift. Within the SCN, cannabinoids were excitatory by a mechanism based on presynaptic CB1R attenuation of axonal GABA release. These data raise the possibility that the time dissociation described by cannabinoid users may result in part from altered circadian clock function and/or entrainment to environmental time cues.

Setdb1 histone methyltransferase regulates mood-related behaviors and expression of the NMDA receptor subunit NR2B.

Histone methyltransferases specific for the histone H3-lysine 9 residue, including Setdb1 (Set domain, bifurcated 1)/Eset/Kmt1e are associated with repressive chromatin remodeling and expressed in adult brain, but potential effects on neuronal function and behavior remain unexplored. Here, we report that transgenic mice with increased Setdb1 expression in adult forebrain neurons show antidepressant-like phenotypes in behavioral paradigms for anhedonia, despair, and learned helplessness. Chromatin immunoprecipitation in conjunction with DNA tiling arrays (ChIP-chip) revealed that genomic occupancies of neuronal Setdb1 are limited to <1% of annotated genes, which include the NMDA receptor subunit NR2B/Grin2B and other ionotropic glutamate receptor genes. Chromatin conformation capture and Setdb1-ChIP revealed a loop formation tethering the NR2B/Grin2b promoter to the Setdb1 target site positioned 30 kb downstream of the transcription start site. In hippocampus and ventral striatum, two key structures in the neuronal circuitry regulating mood-related behaviors, Setdb1-mediated repressive histone methylation at NR2B/Grin2b was associated with decreased NR2B expression and EPSP insensitivity to pharmacological blockade of NR2B, and accelerated NMDA receptor desensitization consistent with a shift in NR2A/B subunit ratios. In wild-type mice, systemic treatment with the NR2B antagonist, Ro25-6981 [R-(R,S)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperidine propranol], and hippocampal small interfering RNA-mediated NR2B/Grin2b knockdown resulted in behavioral changes similar to those elicited by the Setdb1 transgene. Together, these findings point to a role for neuronal Setdb1 in the regulation of affective and motivational behaviors through repressive chromatin remodeling at a select set of target genes, resulting in altered NMDA receptor subunit composition and other molecular adaptations.

miR775 integrates light, sucrose and auxin associated pathways to regulate root growth in Arabidopsis thaliana.

MicroRNAs (miRNAs), a class of single-stranded non-coding RNA of 20-24 nucleotides, regulate gene expression by target gene transcript cleavage or translation inhibition. The phytohormone auxin is a crucial regulator of almost every process involved in plant growth and development. Several studies have demonstrated the involvement of miRNA(s) in the regulation of the auxin signaling pathway and plant development. However, very few studies have identified the auxin-mediated regulation of miRNA(s). In this study, we reveal the detailed mechanism of auxin-mediated regulation of the cell wall-related miR775- Galactosyl transferase (GalT) module, which plays an important role in root growth in Arabidopsis thaliana. We also showed two interdependent mechanisms by which miR775 regulates root growth: miR775-GalT and light-mediated sucrose-dependent pathways. Treatment of GUS reporter lines with Indole Acetic Acid (IAA), sucrose, and light apparently enhanced the abundance of miR775 in root tissue. miR775 overexpressing (miR775OX) lines showed changes in root architecture, including increased primary root growth and root hair, by targeting GalT. miR775OX lines also showed tolerance toward low Pi. These results provide new insights into the auxin regulation of cell wall-related miR775 and suggest its significant role in plant root growth and development by modifying the cell wall.

Two R7 regulator of G-protein signaling proteins shape retinal bipolar cell signaling.

RGS7, RGS11, and their binding partner Gbeta5 are localized to the dendritic tips of retinal ON bipolar cells (ON-BPC), where mGluR6 responds to glutamate released from photoreceptor terminals by activation of the RGS7/RGS11 substrate, Galphao. To determine their functions in retinal signaling, we investigated cell-specific expression patterns of RGS7 and RGS11 by immunostaining, and measured light responses by electroretinography in mice with targeted disruptions of the genes encoding them. RGS7 staining is present in dendritic tips of all rod ON-BPC, but missing in those for subsets of cone ON-BPC, whereas the converse was true for RGS11 staining. Genetic disruption of either RGS7 or RGS11 produced delays in the ON-BPC-derived electroretinogram b-wave, but no changes in the photoreceptor-derived a-wave. Homozygous RGS7 mutant mice had delays in rod-driven b-waves, whereas RGS11 mutant mice had delays in rod-driven, and especially in cone-driven b-waves. The b-wave delays were further enhanced in mice homozygous for both RGS7 and RGS11 gene disruptions. Thus, RGS7 and RGS11 act in parallel to regulate the kinetics of ON bipolar cell responses, with differential impacts on the rod and cone pathways.

CRF receptor blockade prevents initiation and consolidation of stress effects on affect in the predator stress model of PTSD.

Post traumatic stress disorder (PTSD) is a chronic anxiety disorder initiated by an intensely threatening, traumatic event. There is a great need for more efficacious pharmacotherapy and preventive treatments for PTSD. In animals, corticotropin-releasing factor (CRF) and the CRF1 receptor play a critical role in behavioural and neuroendocrine responses to stress. We tested the hypothesis that CRF1 activation is required for initiation and consolidation of long-term effects of trauma on anxiety-like behaviour in the predator exposure (predator stress) model of PTSD. Male C57BL6 mice were treated with the selective CRF1 antagonist CRA0450 (2, 20 mg/kg) 30 min before or just after predator stress. Long-term effects of stress on rodent anxiety were measured 7 d later using acoustic startle, elevated plus maze (EPM), light/dark box, and hole-board tests. Predator stress increased startle amplitude and delayed startle habituation, increased time in and decreased exits from the dark chamber in the light/dark box test, and decreased risk assessment in the EPM. CRF1 antagonism had limited effects on these behaviours in non-stressed controls, with the high dose decreasing risk assessment in the EPM. However, in stressed animals CRF1 antagonism blocked initiation and consolidation of stressor effects on startle, and returned risk assessment to baseline levels in predator-stressed mice. These findings implicate CRF1 activation in initiation and post-trauma consolidation of predator stress effects on anxiety-like behaviour, specifically on increased arousal as measured by exaggerated startle behaviours. These data support further research of CRF1 antagonists as potential prophylactic treatments for PTSD.

Vascular endothelial growth factor attenuates status epilepticus-induced behavioral impairments in rats.

Vascular endothelial growth factor (VEGF) is a vascular growth factor more recently recognized as a neurotrophic factor (for review, see Storkebaum E, Lambrechts D, Carmeliet P. BioEssays 2004;26:943-54). We previously reported that endogenous VEGF protein is dramatically upregulated after pilocarpine-induced status epilepticus in the rat, and that intra-hippocampal infusions of recombinant human VEGF significantly protected against the loss of hippocampal CA1 neurons in this model (Nicoletti JN, Shah SK, McCloskey DP, et al. Neuroscience 2008;151:232-41). We hypothesized that we would see a preservation of cognitive and emotional functioning with VEGF treatment accompanying the neuroprotection previously observed in this paradigm. Using the Morris water maze to evaluate learning and memory, and the light-dark task to assess anxiety, we found a selective profile of preservation. Specifically, VEGF completely preserved normal anxiety functioning and partially but significantly protected learning and memory after status epilepticus. To determine whether the ability of VEGF to attenuate behavioral deficits was accompanied by sustained preservation of hippocampal neurons, we stereologically estimated CA1 pyramidal neuron densities 4 weeks after status epilepticus. At this time point, we found no significant difference in neuronal densities between VEGF- and control-treated status epilepticus animals, suggesting that VEGF could have protected hippocampal functioning independent of its neuroprotective effect.