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Found 11094 matches for

  • Ca2+/calmodulin-dependent protein kinase II and protein kinase C phosphorylate a synthetic peptide corresponding to a sequence that is specific for the gamma 2L subunit of the GABAA receptor.

    23 July 2018

    The gamma 2 subunit of the GABA receptor (GABAA-R) is alternatively spliced. The long variant (gamma 2L) contains eight additional amino acids that possess a consensus sequence site for protein phosphorylation. Previous studies have demonstrated that a peptide or fusion protein containing these eight amino acids is a substrate for protein kinase C (PKC), but not cyclic AMP-dependent protein kinase A (PKA)-stimulated phosphorylation. We have examined the ability of PKA, PKC, and Ca2+/calmodulin-dependent protein kinase (CAM kinase II) to phosphorylate a synthetic peptide corresponding to residues 336-351 of the intracellular loop of the gamma 2L subunit and inclusive of the alternatively spliced phosphorylation consensus sequence site. PKC and CAM kinase II produced significant phosphorylation of this peptide, but PKA was ineffective. The Km values for PKC- and CAM kinase II-stimulated phosphorylation of this peptide were 102 and 35 microM, respectively. Maximal velocities of 678 and 278 nmol of phosphate/min/mg were achieved by PKC and CAM kinase II, respectively. The phosphorylation site in the eight-amino-acid insert of the gamma 2L subunit has been shown to be necessary for ethanol potentiation of the GABAA-R. Thus, our results suggest that PKC, CAM kinase II, or both may play a role in the effects of ethanol on GABAergic function.

  • Protein phosphorylation and neuronal function.

    23 July 2018

    Studies in the past several years have provided direct evidence that protein phosphorylation is involved in the regulation of neuronal function. Electrophysiological experiments have demonstrated that three distinct classes of protein kinases, i.e., cyclic AMP-dependent protein kinase, protein kinase C, and CaM kinase II, modulate physiological processes in neurons. Cyclic AMP-dependent protein kinase and kinase C have been shown to modify potassium and calcium channels, and CaM kinase II has been shown to enhance neurotransmitter release. A large number of substrates for these protein kinases have been found in neurons. In some cases (e.g., tyrosine hydroxylase, acetylcholine receptor, sodium channel) these proteins have a known function, whereas most of these proteins (e.g., synapsin I) had no known function when they were first identified as phosphoproteins. In the case of synapsin I, evidence now suggests that it regulates neurotransmitter release. These studies of synapsin I suggest that the characterization of previously unknown neuronal phosphoproteins will lead to the elucidation of previously unknown regulatory processes in neurons.

  • Phosphorylation-mediated changes in pyruvate dehydrogenase activity influence pyruvate-supported calcium accumulation by brain mitochondria.

    23 July 2018

    Changes in the activity of pyruvate dehydrogenase [pyruvate:lipoamide oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1, PDH], elicited by inhibition of the phosphorylation of its 40,000 Mr alpha-subunit, were compared with changes in pyruvate-supported calcium accumulation by rat brain mitochondria. Dichloroacetate (DCA) produces concentration-dependent inhibition of the phosphorylation of intramitochondrial PDH alpha-subunit, which is accompanied by stimulation of PDH activity and calcium accumulation. DCA did not affect succinate- or ATP-supported mitochondrial calcium accumulation. The concentration of DCA giving half-maximal inhibition of the phosphorylation was almost identical to that giving half-maximal stimulation of PDH activity and calcium accumulation. PDH activity and pyruvate-supported calcium accumulation showed similar dependence on pyruvate concentration with respective apparent affinities for pyruvate of 40 microM and 30 microM, and both activities exhibited positive cooperativity. DCA modified only the maximal activity of PDH or the maximal calcium DCA modified only the maximal activity of PDH or the maximal calcium accumulation without changing either the apparent affinities for pyruvate or calcium or the Hill coefficients. These data provide evidence that calcium accumulation by mitochondria is tightly linked to PDH activity and that changes in the phosphorylation of the PDH alpha-subunit can be reflected in changes in the calcium-buffering ability of mitochondria. This suggests a possible mechanism by which a variety of manipulations, such as repetitive synaptic stimulation, can alter the regulation of internal calcium levels.

  • Biochemical and physiological studies of long-term synaptic plasticity.

    23 July 2018

    High frequency stimulation of fiber systems in the mammalian hippocampus produces a semipermanent increase in synaptic efficacy. This effect, long-term potentiation (LTP), has been of considerable interest as a potential substrate of memory due to its rapid onset and extreme persistence. Experiments are described that indicate that the locus of LTP is confined to the synaptic complex of the fibers stimulated; further, Ca2+ is shown to be essential for the initiation of LTP and may play a role in triggering this increase in synaptic efficiency. Data from biochemical analyses of LTP indicate that a 40,000 dalton synaptic membrane protein shows a highly reliable change in its endogenous phosphorylation following high frequency hippocampal stimulation. Phosphorylase kinase, a Ca2+ sensitive enzyme, is shown to specifically catalyse the phosphorylation of this 40,000 dalton protein. The data are discussed in terms of a working model in which the Ca2+ dependent phosphorylation of the 40,000 dalton protein produced by high frequency stimulation is a biochemical intermediate in the production of LTP.

  • A single episode of neonatal seizures permanently alters glutamatergic synapses.

    23 July 2018

    OBJECTIVE: The contribution of seizures to cognitive changes remains controversial. We tested the hypothesis that a single episode of neonatal seizures (sNS) on rat postnatal day (P) 7 permanently impairs hippocampal-dependent function in mature (P60) rats because of long-lasting changes at the synaptic level. METHODS: sNS was induced with subcutaneously injected kainate on P7. Learning, memory, mossy fiber sprouting, spine density, hippocampal synaptic plasticity, and glutamate receptor expression and subcellular distribution were measured at P60. RESULTS: sNS selectively impaired working memory in a hippocampal-dependent radial arm water-maze task without inducing mossy fiber sprouting or altering spine density. sNS impaired CA1 hippocampal long-term potentiation and enhanced long-term depression. Subcellular fractionation and cross-linking, used to determine whether glutamate receptor trafficking underlies the alterations of memory and synaptic plasticity, demonstrated that sNS induced a selective reduction in the membrane pool of glutamate receptor 1 subunits. sNS induced a decrease in the total amount of N-methyl-D-aspartate receptor 2A and an increase in the primary subsynaptic scaffold, PSD-95. INTERPRETATION: These molecular consequences are consistent with the alterations in plasticity and memory caused by sNS at the synaptic level. Our data demonstrate the cognitive impact of sNS and associate memory deficits with specific alterations in glutamatergic synaptic function.

  • Ethanol's inhibition of LTP may not be mediated solely via direct effects on the NMDA receptor.

    23 July 2018

    Acute abuse of alcohol is well known to have deleterious effects on memory. However, the molecular and cellular bases of this effect are not well understood. Ethanol is known to inhibit long-term potentiation (LTP), a putative cellular substrate of memory. However, there is controversy concerning the doses of ethanol required for inhibition of LTP. We examined the doses of ethanol required to inhibit LTP in the CA1 region of the hippocampus. We used two different LTP-inducing paradigms in these studies and found that only doses of ethanol associated with profound intoxication (50-100 mM) can produce significant inhibition of LTP. We also investigated the molecular mechanisms of ethanol's effect on LTP. Activation of the N-methyl-D-aspartate receptor plays a critical role in LTP, and ethanol has been shown to partially inhibit N-methyl-D-aspartate receptor function. We tested directly whether the level of N-methyl-D-aspartate inhibition produced by 100 mM ethanol is sufficient to account for the complete inhibition of LTP produced by 100 mM ethanol. Our data suggest that ethanol's effects on the N-methyl-D-aspartate receptor can account for most, but not all of ethanol's inhibition of LTP.

  • G-protein-coupled receptors act via protein kinase C and Src to regulate NMDA receptors.

    23 July 2018

    The N-methyl-D-aspartate (NMDA) receptor contributes to synaptic plasticity in the central nervous system and is both serine-threonine and tyrosine phosphorylated. In CA1 pyramidal neurons of the hippocampus, activators of protein kinase C (PKC) as well as the G-protein-coupled receptor ligands muscarine and lysophosphatidic acid enhanced NMDA-evoked currents. Unexpectedly, this effect was blocked by inhibitors of tyrosine kinases, including a Src required sequence and an antibody selective for Src itself. In neurons from mice lacking c-Src, PKC-dependent upregulation was absent. Thus, G-protein-coupled receptors can regulate NMDA receptor function indirectly through a PKC-dependent activation of the non-receptor tyrosine kinase (Src) signaling cascade.

  • Sulindac improves memory and increases NMDA receptor subunits in aged Fischer 344 rats.

    23 July 2018

    Inflammatory processes in the central nervous system are thought to contribute to Alzheimer's disease (AD). Chronic administration of nonsteroidal anti-inflammatory drugs (NSAIDs) decreases the incidence of Alzheimer's disease. There are very few studies, however, on the cognitive impact of chronic NSAID administration. The N-methyl-d-aspartate (NMDA) receptor is implicated in learning and memory, and age-related decreases in the NMDA NR2B subunit correlate with memory deficits. Sulindac, an NSAID that is a nonselective cyclooxygenase (COX) inhibitor was chronically administered to aged Fischer 344 rats for 2 months. Sulindac, but not its non-COX active metabolite, attenuated age-related deficits in learning and memory as assessed in the radial arm water maze and contextual fear conditioning tasks. Sulindac treatment also attenuated an age-related decrease in the NR1 and NR2B NMDA receptor subunits and prevented an age-related increase in the pro-inflammatory cytokine, interleukin 1beta (IL-1beta), in the hippocampus. These findings support the inflammation hypothesis of aging and have important implications for potential cognitive enhancing effects of NSAIDs in the elderly.

  • Amelioration of age-related deficits in the stimulation of synapsin phosphorylation.

    23 July 2018

    In a previous report we demonstrated that aged (24-26 month) rats have deficits in long-term potentiation, a form of synaptic enhancement that is dependent on protein phosphorylation (Moore et al., Hippocampus, 3:57-66; 1993). In the present study we demonstrate that aged rats have a deficit in the phosphorylation of the synaptic vesicle associated protein synapsin I. Specifically, aged animals exhibit defective phorbol ester-induced stimulation of synapsin phosphorylation at its calcium/calmodulin dependent protein kinase II sites. We also examined the effects of caloric restriction and antioxidant therapy on this age-related deficit. We found that either life-long caloric restriction or treatment with 16 mg/kg N-tert-butyl-alpha-phenylnitrone (PBN) for 2 weeks can at least partially ameliorate the age-related deficit in the phorbol ester stimulation of synapsin phosphorylation.

  • Actions of A-75200, a novel catecholamine uptake inhibitor, on norepinephrine uptake and release from bovine adrenal chromaffin cells.

    23 July 2018

    The balance between catecholamine (CA) release and reuptake is closely regulated and determines the effective level of transmitter at the synaptic cleft. Drugs that block CA uptake have potential utility as antidepressant medications. One such drug is racemic (+/-)-(1' R*,3R*)-3-phenyl-1-[1',2',3',4'-tetrahydro-5',6'- methylenedioxy-1'-naphthalenyl-methyl]-pyrrolidine methanesulfonate (A-7500), a novel polycyclic compound developed at Abbott Laboratories. This compound is known to bind to CA transporters in the central nervous system, however, its effects on an intact neurosecretory system have not been studied. In this regard, norepinephrine (NE) release from bovine adrenal chromaffin cells (BACC) is a classic model system for CA release and is an excellent system in which to examine the effects of drugs which modulate neurotransmitter release. We compared the effects of A-75200 and its two constituent enantiomers, A-74111 and A-74112, to the effects of three well-characterized uptake inhibitors, desipramine (DMI), nomifensine and cocaine. We found that the Abbott compounds inhibit [3H]norepinephrine ([3H]NE) uptake with an EC50 comparable to cocaine. In addition, unlike nomifensine and cocaine, these compounds inhibited nicotine- and K(+)-stimulated NE release, whereas histamine-stimulated release was preserved. Thus, the Abbott compounds block the effects on secretion of two agonists (nicotine and K+) which depend on a depolarization-dependent influx of extracellular calcium. We conclude that in addition to blocking NE uptake by inhibiting the NE transporter, the Abbott compounds may modulate peripheral NE release by inhibiting calcium flux through voltage-gated channels. This study demonstrates the utility of bovine adrenal chromaffin cells for preclinical trials of drugs that affect catecholaminergic neurotransmission.

  • Oxford receives 9 Million GBP in Collaboration for Leadership in Applied Health Research and Care

    12 August 2013

    The National Institute for Health Research announces 24 Million GBP funding for 13 new Collaborations for Leadership in Applied Health Research and Care (CLAHRCs) to help tackle major health challenges. Lord Howe, Health Minister said: This is great news for patients - this funding could potentially help the development of ground breaking treatments which could revolutionize care. With a growing elderly population, the need for innovative and effective solutions has never been more important (NIHR Website, see quote below).

  • BBC File on 4: Dementia - what do we know?

    2 March 2016

    Prof Simon Lovestone features in this investigative radio programme that explores the balance for the need for more research with the need for better care for people living with dementia.

  • How internet affects young people at risk of self-harm or suicide

    1 November 2013

    Oxford researchers have found internet forums provide a support network for socially isolated young people. However, they also conclude that the internet is linked to an increased risk of suicide and self-harm among vulnerable adolescents.

  • Stressful trigger events associated with risk of violent crime

    18 July 2016

    A study led, by the Department of Psychiatry's Prof Seena Fazel, suggests trigger events, including exposure to violence, were associated with increased risk of violent crime in the week following exposure among patients with schizophrenia and bipolar disorder and among individuals without psychiatric diagnoses who were included for comparison.

  • How Ruby Wax trained her brain to beat depression

    3 June 2013

    Mail Online, 02/06/2013, see Lydia Slater's Article on how comedian Ruby Wax has learned to manage depression through studying mindfulness and neuroscience describes how she studied on an Oxford University master’s course run by mindfulness-based cognitive therapy co-founder Professor Mark Williams.

  • The impact of self-harm on the whole family

    25 January 2016

    Self-harm in young people is a large and growing problem. A young person’s self-harming behaviour can have an impact on the entire family, but very little research has explored this topic.

  • Tetris used to prevent post-traumatic stress symptoms

    3 April 2017

    A single dose psychological intervention, which includes using the computer game Tetris, can prevent the unpleasant, intrusive memories that develop in some people after suffering a traumatic event.

  • Bid to prevent Alzheimer’s dementia signs up first study recruit

    11 May 2016

    A major study to find interventions that prevent the onset of Alzheimer’s dementia has recruited its first participant.

  • Top 10 Depression Research Priorities

    2 February 2016

    The Depression: ARQ project has identified the most important research priorities according to people affected by depression, their friends and family, and health care professionals.

  • Prof Andrea Cipriani leads 4th Course in Oxford on Network Meta-Analysis

    1 February 2017

    Dates have been set for this year's summer school on Network Meta-Analysis