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  • Correlated changes in NMDA receptor phosphorylation, functional activity, and sedation by chronic ethanol consumption.

    23 July 2018

    Alcohol abuse leads to tolerance, dependence, and memory impairments that involve excitatory glutamatergic NMDA synaptic transmission. The NMDA receptor (NMDAR) is known to undergo activity-dependent adaptive functional changes. Since we observed that acute ethanol inhibition of the NMDAR was regulated by protein tyrosine phosphorylation, we investigated the role of protein tyrosine kinases and phosphatases on the NMDAR functions by chronic ethanol treatment. We carried out whole-cell recording, western blotting, and behavioral righting reflex measurements to assess the impact of chronic ethanol treatment on NMDAR function. Our results indicated that these receptors became resistant to the acute ethanol inhibition following chronic ethanol consumption. This resistance occurred without an increase in the NMDAR subunit expression but was associated with decreases in the levels of phospho-Y-1472 NR2B, increases in the levels of STEP33, increases in phospho-p38 mitogen-activated protein kinase (pp38 MAPK), and acquisition of tolerance to the sedative effects of ethanol. These data suggested that altered protein tyrosine phosphorylation of the NMDAR subunits significantly contributes to functional changes of this receptor by chronic ethanol ingestion. Therefore, preservation of the integrity of tyrosine phosphorylation mechanisms of the NMDAR may be important in controlling the progression of alcohol tolerance and dependence.

  • Regulation of N-methyl-D-aspartate receptor function by constitutively active protein kinase C.

    23 July 2018

    The ability of the constitutively active fragment of protein kinase C (PKM) to modulate N-methyl-D-aspartate (NMDA)-activated currents in cultured mouse hippocampal neurons and acutely isolated CA1 hippocampal neurons from postnatal rats was studied using patch-clamp techniques. The responses of two heterodimeric combinations of recombinant NMDA receptors (NR1a/NR2A and NR1a/NR2B) expressed in human embryonic kidney 293 cells were also examined. Intracellular applications of PKM potentiated NMDA-evoked currents in cultured and isolated CA1 hippocampal neurons. This potentiation was observed in the absence or presence of extracellular Ca2+ and was prevented by the coapplication of the inhibitory peptide protein kinase inhibitor(19-36). Furthermore, the PKM-induced potentiation was not a consequence of a reduction in the sensitivity of the currents to voltage-dependent blockade by extracellular Mg2+. We also found different sensitivities of the responses of recombinant NMDA receptors to the intracellular application of PKM. Some potentiation was observed with the NR1a/NR2A subunits, but none was observed with the NR1a/NR2B combination. Applications of PKM to inside-out patches taken from cultured neurons increased the probability of channel opening without changing single-channel current amplitudes or channel open times. Thus, the activation of protein kinase C is associated with potentiation of NMDA receptor function in hippocampal neurons largely through an increase in the probability of channel opening.

  • Protein kinase C enhances recombinant bovine alpha 1 beta 1 gamma 2L GABAA receptor whole-cell currents expressed in L929 fibroblasts.

    23 July 2018

    The beta 1 and gamma 2L subunits of the gamma-aminobutyric acid type A receptor (GABAR) contain phosphorylation sites for PKC. To determine the effect of PKC on GABAR function, whole-cell recordings were obtained from mouse fibroblasts expressing recombinant alpha 1 beta 1 gamma 2L receptors, and catalytically active PKC (PKM) was applied via the recording pipette. The first experiment was a population study. Intracellular application of PKM increased GABAR currents, and the enhancement was antagonized by coapplication of the PKC inhibitory peptide. No acceleration or deceleration of GABAR desensitization was observed. The second experiment was a reimpalement study in which paired recordings were made successively from individual cells. Enhancement of GABAR currents by PKM was again obtained. PKM increased GABAR currents at high (> 10 microM) but not at low (< 10 microM) GABA concentrations, resulting in increases in both EC50 and maximal GABAR current. Thus, PKC phosphorylation enhanced recombinant alpha 1 beta 1 gamma 2L GABAR current by increasing maximal current without increasing the affinity of GABA for the GABARs.

  • Immunochemical characterization of the beta 2 subunit of the GABAA receptor.

    23 July 2018

    To date three beta subunits of the GABAA receptor have been identified in rat brain as a result of cDNA library screening. The beta 2 subunit has been reported to have a wide distribution in rat brain based on in situ hybridization studies quantifying beta 2 mRNA. To study the beta 2 subunit more directly, we have raised a polyclonal antibody to a synthetic peptide representing residues 315-334 of the intracellular loop of the beta 2 subunit. The antibody, which had been affinity-purified, recognized the beta 2 peptide but did not immunolabel homologous beta 1 and beta 3 subunit peptides, indicating that this antibody is specific for the beta 2 subunit of the receptor. In western blots of the purified receptor, the antibody recognized a major diffuse band of 54-58 kDa and exhibited minor labeling of lower-molecular-mass polypeptides. In western blots of cortex homogenate, the antibody exhibited nervous system-specific labeling of a 55-kDa band that comigrated with the 55-kDa band of the purified receptor. Quantitative immunolabeling of this 55-kDa polypeptide permitted direct determination of the relative amounts of the beta 2 subunit in different brain regions. The brainstem contained the highest relative specific activity of the beta 2 subunit, followed by the inferior colliculus, olfactory lobe, and cerebellum. Lower levels of immunolabeling were seen in hypothalamus, hippocampus, thalamus, and cortex.

  • Ethanol has no effect on cAMP-dependent protein kinase-, protein kinase C-, or Ca(2+)-calmodulin-dependent protein kinase II-stimulated phosphorylation of highly purified substrates in vitro.

    23 July 2018

    The actions of ethanol on kinase stimulated phosphorylation were examined using highly purified protein kinases and a variety of purified substrates. Ethanol (25-200 mM) failed to alter the phosphorylation of histone IIa and histone IIIs by cAMP-dependent protein kinase (PKA) and protein kinase C (PKC), respectively. Moreover, ethanol (25-200 mM) did not affect the phosphorylation of synapsin I by Ca(2+)-calmodulin-dependent protein kinase II (CAM kinase II). Finally, neither PKA nor PKC stimulated phosphorylation of the GABAA receptor (GABAA-R) was modulated by ethanol at any concentration of ethanol tested. These results suggest that ethanol, in pharmacological concentrations, has no direct actions on the ability of these kinases to catalyze the phosphorylation of specific substrate proteins. In particular, ethanol does not appear to directly influence GABAA-R phosphorylation by either PKA or PKC.

  • Phosphorylation-independent effects of second messenger system modulators on gamma-aminobutyric acidA receptor complex function.

    23 July 2018

    Recent studies investigating the functional significance of gamma-aminobutyric acidA (GABAA) receptor complex phosphorylation have employed membrane-permeant compounds to manipulate second messenger systems. Although these compounds affect GABAA receptor function, the dependence of these effects on phosphorylation has not been established. Here we report that several second messenger system modulations can decrease GABAA receptor function independently of their effects on protein phosphorylation. Brain membrane vesicles were lysed and resealed in the presence of EDTA to chelate internal Mg2+. Under these conditions, phosphorylation of vesicle proteins was almost completely inhibited, as determined by incorporation of 32P into phosphoproteins. In these lysed/resealed vesicles, an inhibition of muscimol-stimulated 36Cl- uptake was observed with the cAMP analogs 8-(4-chlorophenylthio)-cAMP, N6,O2'-dibutyryl-cAMP, and 8-bromo-cAMP, the protein kinase inhibitor H7, and the adenylate cyclase activator forskolin. In both intact and EDTA-treated lysed/resealed microsacs, cAMP analogs and H7 inhibited binding of the GABAA receptor ligand [3H]SR 95531 at concentrations shown to inhibit muscimol-stimulated 36Cl- uptake. Forskolin was observed to inhibit the binding of t-butylbicyclophosphoro-[35S]thionate, a ligand that binds to a site on the chloride channel. These results demonstrate that compounds commonly used to alter second messenger systems affect the receptor sites and function of the GABAA receptor chloride channel by mechanisms that do not involve protein phosphorylation. In light of these findings, results obtained with these compounds should be interpreted with caution.

  • Microvesicles of the neurohypophysis are biochemically related to small synaptic vesicles of presynaptic nerve terminals.

    23 July 2018

    Nerve endings of the posterior pituitary are densely populated by dense-core neurosecretory granules which are the storage sites for peptide neurohormones. In addition, they contain numerous clear microvesicles which are the same size as small synaptic vesicles of typical presynaptic nerve terminals. Several of the major proteins of small synaptic vesicles of presynaptic nerve terminals are present at high concentration in the posterior pituitary. We have now investigated the subcellular localization of such proteins. By immunogold electron microscopy carried out on bovine neurohypophysis we have found that three of these proteins, synapsin I, Protein III, and synaptophysin (protein p38) were concentrated on microvesicles but were not detectable in the membranes of neurosecretory granules. In addition, we have studied the distribution of the same proteins and of the synaptic vesicle protein p65 in subcellular fractions of bovine posterior pituitaries obtained by sucrose density centrifugation. We have found that the intrinsic membrane proteins synaptophysin and p65 had an identical distribution and were restricted to low density fractions of the gradient which contained numerous clear microvesicles with a size range the same as that of small synaptic vesicles. The peripheral membrane proteins synapsin I and Protein III exhibited a broader distribution extending into the denser part of the gradient. However, the amount of these proteins clearly declined in the fractions preceding the peak of neurosecretory granules. Our results suggest that microvesicles of the neurohypophysis are biochemically related to small synaptic vesicles of all other nerve terminals and argue against the hypothesis that such vesicles represent an endocytic byproduct of exocytosis of neurosecretory granules.

  • Phosphorylation of FMRP and alterations of FMRP complex underlie enhanced mLTD in adult rats triggered by early life seizures.

    23 July 2018

    Outside of Fragile X syndrome (FXS), the role of Fragile-X Mental Retardation Protein (FMRP) in mediating neuropsychological abnormalities is not clear. FMRP, p70-S6 kinase (S6K) and protein phosphatase 2A (PP2A) are thought to cooperate as a dynamic signaling complex. In our prior work, adult rats have enhanced CA1 hippocampal long-term depression (LTD) following an early life seizure (ELS). We now show that mGluR-mediated LTD (mLTD) is specifically enhanced following ELS, similar to FMRP knock-outs. Total FMRP expression is unchanged but S6K is hyperphosphorylated, consistent with S6K overactivation. We postulated that either disruption of the FMRP-S6K-PP2A complex and/or removal of this complex from synapses could explain our findings. Using subcellular fractionation, we were surprised to find that concentrations of FMRP and PP2A were undisturbed in the synaptosomal compartment but reduced in parallel in the cytosolic compartment. Following ELS FMRP phosphorylation was reduced in the cytosolic compartment and increased in the synaptic compartment, in parallel with the compartmentalization of S6K activation. Furthermore, FMRP and PP2A remain bound following ELS. In contrast, the interaction of S6K with FMRP is reduced by ELS. Blockade of PP2A results in enhanced mLTD; this is occluded by ELS. This suggests a critical role for the location and function of the FMRP-S6K-PP2A signaling complex in limiting the amount of mLTD. Specifically, non-synaptic targeting and the function of the complex may influence the "set-point" for regulating mLTD. Consistent with this, striatal-enriched protein tyrosine phosphatase (STEP), an FMRP "target" which regulates mLTD expression, is specifically increased in the synaptosomal compartment following ELS. Further, we provide behavioral data to suggest that FMRP complex dysfunction may underlie altered socialization, a symptom associated and observed in other rodent models of autism, including FXS.

  • The hospital costs of self-harm

    8 September 2017

    Study reveals the health service costs for hospital care of people who self-harm, emphasising the need for effective clinical services and prevention initiatives.

  • Adam Al-Diwani wins the Margaret Temple Award

    8 November 2017

    Wellcome DPhil Training Fellowship researcher is awarded BMA grant given to assist research into schizophrenia.

  • Trust Me I'm a Doctor: Mental Health Special

    1 November 2017

    On 1 November, BBC Two's flagship medical show focuses on two areas of research at the Department of Psychiatry. Find out more about the research here.

  • Oxford Dementia Research Day

    30 May 2017

    NIHR Oxford Health Biomedical Research Centre and ARUK Oxford Local Network are jointly hosting the annual Oxford Dementia Research Day.

  • A tribute: Elisa Favaron

    5 February 2018

    Valeria Frighi honours friend and colleague, Elisa Favaron, who tragically passed away on 19th January 2018 from breast cancer.

  • Major award to develop VR treatment in the NHS for mental health disorders

    5 February 2018

    The National Institute of Health Research (NIHR) awarded £4 million to enable state-of-the-art psychological therapy to be delivered via virtual reality (VR) in the NHS.

  • 5th Course on Network Meta-Analysis

    5 February 2018

    Andrea Cipriani leads this 3-day interactive course with lectures, group work, hands-on tutorials and supervised statistical sessions for clinicians, researchers and policy makers.

  • Even moderate drinking linked to a decline in brain health, finds study

    7 June 2017

    Moderate alcohol consumption is associated with increased risk of adverse brain outcomes and steeper decline in cognitive skills, finds a study led by Dr Anya Topiwala at the Department of Psychiatry, and published by The BMJ.

  • Department of Psychiatry researchers join the Curiosity Carnival

    26 September 2017

    Curiosity Carnival is part of European Researchers’ Night. This is the first time that the University has taken part, and activities will be taking place across the city on 29 September.

  • Time to vote!

    20 May 2014

    Contested Elections: 12 June 2014 One member of Congregation elected by Congregation from members of the faculties in the Divisions of Mathematical, Physical and Life Sciences and of Medical Sciences

  • Can brief daily mental exercises change the way the human brain processes certain kinds of information?

    20 June 2017

    The aim of this study is to investigate the effects of certain brief mental exercises on the way in which the brain processes specific kinds of information. We are looking for healthy participants (both male and female), aged 18 to 65 years. In order to participate, you must be in good health, not be regularly engaged in any kind of formal mental exercises (e.g. yoga, meditation, mindfulness practices, positive psychology exercises, psychotherapy etc.) and you must not have a history of any mental disorder (such as depression, anxiety disorder, or eating disorder). You would be invited to the Department of Psychiatry (Warneford Hospital) for two study sessions. Both sessions would take approximately 60 to 90 minutes. Between the sessions you would be assigned a brief mental exercise (taking approximately 10 minutes per day) and you would be asked to carry out this exercise each evening for 7 days. After practising for 7 days, your performance on a range of computerized psychological tasks would be assessed. If you are interested and would like more information, please contact Dr Alexander Kaltenboeck (alexander.kaltenboeck@psych.ox.ac.uk) at the Department of Psychiatry. Ethics Approval Reference: R49254/RE003

  • Friends of Oxford Dementia and Ageing Research (OxDARE)

    27 March 2018

    Anyone who is interested in finding out more about dementia and ageing research in Oxford is invited to become a Friend of OxDARE. Friends can choose to register an interest in taking part in future studies and/or receive quarterly newsletters. When new studies get underway, OxDARE researchers will invite interested Friends to take part by email. If you are contacted by one of our researchers, it is your choice whether you would like to participate in their study or not.

  • Volunteers needed for a Virtual Reality Study!

    27 March 2018

    One 45 minute session

  • Are spiders a problem for you?

    28 November 2017

    We are looking for healthy volunteers aged 18-60 years and fluent in English to take part in a study investigating how a single dose of the medication hydrocortisone affects attention for spiders, using simple computer tasks. Hydrocortisone is a stress hormone also naturally occurring in the body. However, we think that it may also enhance the effectiveness of psychological therapies such as Cognitive-Behaviour Therapy. The study involves four appointments of about 5 hours in total.

  • Neural mechanisms underlying decision making

    6 March 2018

    Who are we looking for? Healthy fluent English-speaking people aged 18-85 who are not pregnant. You will be asked questions about your medical history to check your suitability for an MRI scan. MRI is a method to measure brain activity that allows us to see how the brain is organised, processes information and performs skills like speech or memory. This scan is safe and does not involve any needles or injections.