Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Exogenous delivery of the neurotrophic factors, brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3), promotes the function, sprouting and regrowth of 5-HT-containing neurones in the brains of adult rats. Similar infusions of BDNF into the dorsal raphe nucleus produce an antidepressant effect, as evaluated by several 'learned helplessness' paradigms. Environmental stressors such as immobilization induce depression and decrease BDNF mRNA. Antidepressants increase BDNF mRNA in the brain, via 5-HT2A and beta-adrenoceptor subtypes and prevent the stress-induced decreases in BDNF mRNA. In this article, Tony Altar discusses how existing treatments of depression might work by increasing endogenous brain levels of BDNF or NT-3, which in turn could promote monoamine-containing neurone growth and function. Drugs that selectively stimulate the production of neurotrophins could represent a new generation of antidepressants.
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PMID:Neurotrophins and depression. 1010 65

Synaptic plasticity has been implicated in the mechanisms contributing to the shaping of the cortical circuits responsible for the transmission of the visual input in the rat primary visual cortex. However, the degree of plasticity of the thalamocortical synapse may change during development, perhaps reflecting the degree of stabilization of the circuitry subserving it. We have chosen the ability of this synapse to be first depressed and then potentiated as a specific indicator of its plasticity. In this study we have investigated how this parameter changes during development and the factors controlling it. Extracellular field potentials in cortical layers 2/3 were evoked by stimulation of the white matter in rat primary visual cortex slices prepared at different postnatal ages. Low-frequency stimulation (900 pulses at 1 Hz) of the white matter was used to induce long-term depression of field potential amplitude, whereas long-term potentiation was evoked by high-frequency stimulation consisting of three trains at 100 Hz. We provide evidence that while it is possible to potentiate previously depressed synapses soon after eye opening (postnatal day 17) this synaptic characteristic decreases rapidly thereafter. The decrease in this form of cortical synaptic plasticity closely matches the stabilization of the cortical circuitry towards an adult pattern of connectivity and function. Depressed cortical synapses cannot be potentiated in normal rats at postnatal 23, but they can be potentiated in rats reared in the dark from postnatal days 17 to 29. Moreover, application of brain-derived neurotrophic factor, known to be expressed in an activity-dependent manner, was able to restore the ability of synapses to be potentiated after long-term depression, thus indicating its important modulatory role in brain development.
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PMID:A new form of synaptic plasticity is transiently expressed in the developing rat visual cortex: a modulatory role for visual experience and brain-derived neurotrophic factor. 1033 67

Acute effects of neurotrophins on synaptic plasticity have recently received much attention, but the roles of these factors in regulating long-lasting changes in synaptic function remain unclear. To address this issue we studied the long-term (days to weeks) and short-term (minutes to hours) effects of brain-derived neurotrophic factor (BDNF) on excitatory synaptic transmission in autaptic cultures of hippocampal CA1 neurons. We found that BDNF induced long-term enhancement of the strength of non-NMDA receptor-mediated glutamatergic transmission. This upregulation of EPSC amplitude occurred via an increase in the size of unitary synaptic currents, with no significant contribution from other aspects of neuronal electrical and synaptic function including cell size, voltage-gated sodium and potassium current levels, the number and size of synaptic contacts, and the frequency of spontaneous neurotransmitter release. Chronic BDNF treatment also decreased the degree of synaptic depression measured in response to paired stimuli. Thus, BDNF induced long-term synaptic enhancement of both basal and use-dependent synaptic transmission via specific changes to the synapse rather than through generalized potentiation of neuronal growth and differentiation. Finally, we showed that the long-term effects of BDNF are functionally and mechanistically distinct from its acute effects on synaptic transmission, suggesting that, in vivo, BDNF activation of Trk receptors can have different functional effects depending on the time course of its action.
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PMID:Long-term enhancement of central synaptic transmission by chronic brain-derived neurotrophic factor treatment. 1043 57

Long-term desensitization of AMPA receptors (LTDA) is a core mechanism of long-term depression, a model of motor learning in the cerebellum. In this study we investigated the expression of neurotrophic factor genes after induction of LTDA in cultured cerebellar slices. LTDA was induced by application of quisqualate and monitored as a population response with a wedge recording technique. The levels of mRNA were quantified by reverse transcription followed by polymerase chain reaction. Quisqualate, at a dose and duration that reliably induced LTDA, elicited a significant and specific increase in BDNF mRNA with a peak at four hours after the application. By cell fractionation, the major source of BDNF mRNA increase was found to be in granule cells. In addition, a small but significant increase of transcripts with specific exon usage was observed in a Purkinje cell fraction. These results indicate that BDNF may be coinduced with LTDA and suggest that the slow and sustained increase of BDNF mRNA might play a role in later phases of synaptic plasticity in the cerebellum.
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PMID:A stimulus paradigm inducing long-term desensitization of AMPA receptors evokes a specific increase in BDNF mRNA in cerebellar slices. 1046

1. The authors have recently reported a new protocol for inducing long-term depression through activation of GABAA receptors in the hippocampal slices. This long-term depression is reversed by bicuculline and potentiated by neurosteroids such as alphaxalone. It was also shown that glutamate receptor activity is not involved in the induction of this novel type of long-term depression. Brain derived neurotrophic factor is a member of the neurotrophins family widely expressed in the central nervous system. There is increasing evidence that indicate an important role for brain-derived neurotrophic factor in synaptic plasticity. It has been reported that brain-derived neurotrophic factor level is downregulated by GABA system. The present study investigated a possible relation between muscimol-induced long-term depression and brain-derived neurotrophic factor level. 2. Extracellular recordings were made in the CA1 pyramidal cell layer of rat hippocampal slices following orthodromic stimulation of Schaffer collateral fibers in stratum radiatum. 3. It was observed that brain-derived neurotrophic factor at concentration that did not have any effect itself on the population spike, prevents the induction of long-term depression by muscimol. In addition to this, K-252a an inhibitor of Trk type kinase blocked the prevention of muscimol-induced LTD by brain-derived neurotrophic factor. 4. The results suggest that there is an interaction between muscimol-induced long-term depression and brain-derived neurotrophic factor and may explain the post receptor mechanism of muscimol-induced long-term depression through a bilateral relation between GABAA activity and brain-derived neurotrophic factor.
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PMID:Prevention of muscimol-induced long-term depression by brain-derived neurotrophic factor. 1058 43

The hypotheses that cerebral embolic events lead to repetitive episodes of cortical spreading depression (CSD) and that these propagating waves trigger the expression of c-fos, brain-derived neurotrophic factor (BDNF), glial fibrillary acidic protein (GFAP), and heat shock protein 70 (HSP70) mRNA were tested. Wistar rats underwent photochemically induced right common carotid artery thrombosis (CCAT) (n = 18) or sham (n = 8) procedures. In a subgroup of rats (n = 5), laser-Doppler flowmetry probes were placed overlying the right parietal cortex to record CSD-like changes in cortical blood flow during the initial 2-hour postinjury period. Rats were killed by decapitation at 2 or 24 hours after CCAT, and brains were processed for in situ localization of the gene expression. Two to five intermittent transient hyperemic episodes lasting 1 to 2 minutes were recorded ipsilaterally after CCAT. At 2 hours after CCAT, the widespread expression of c-fos and BDNF mRNAs was observed throughout the ipsilateral cerebral cortex. Pretreatment with the N-methyl-D-aspartate receptor blocker MK-801 (2 mg/kg) 1 hour before CCAT reduced the expression of BDNF mRNA expression at 2 hours. At 24 hours after CCAT, increased expression of GFAP mRNA was present in cortical and subcortical regions. In contrast, multifocal regions of HSP70 expression scattered throughout the thrombosed hemisphere were apparent at both 2 and 24 hours after injury. These data indicate that thromboembolic events lead to episodes of CSD and time-dependent alterations in gene expression. The ability of embolic processes to induce widespread molecular responses in neurons and glia may be important in the pathogenesis of transient ischemic attacks and may influence the susceptibility of the postembolic brain to subsequent insults including stroke.
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PMID:Thromboembolic events lead to cortical spreading depression and expression of c-fos, brain-derived neurotrophic factor, glial fibrillary acidic protein, and heat shock protein 70 mRNA in rats. 1061 98

Although an increased recognition of depressive disorders in youth represents a positive conceptual change over the past decades, there still is a very limited amount of research on useful treatment interventions. The paucity of data is particularly keen for the use of psychotropic drugs. For example, by applying the criteria suggested by the International Psychopharmacology Algorithm Project, there barely are enough first-grade ("Level A," meaning at least two RCTs) data supporting the short-term efficacy of antidepressants (the SSRIs) in the treatment of juvenile depression. And yet, limited data have not translated into limited use in routine clinical practice. In fact, the use of antidepressant medications has increased exponentially over the last decade, a change that is especially conspicuous for individuals less than 18 years of age. The perceived safety of the SSRIs and other novel antidepressants is partly at the root of their increased popularity. Data regarding their safety are likewise quite limited, however, and essentially are nonexistent for longer-term use. Based on the reviewed data, a medication algorithm for the treatment of early-onset depression can be suggested (Fig. 1). The algorithm underscores the need for adequate evaluation and diagnostic assessment, with particular attention to comorbid conditions (such as a bipolar diathesis) that may dictate alternative treatment strategies. In general, psychotherapy is the initial approach to juvenile MDD, with medication use reserved for more severe cases or those not responding to psychotherapy alone. Given that only two types of psychotherapy and two SSRIs have adequate controlled short-term efficacy data, all but the initial steps must be undertaken guided by clinical judgment and an individualized risk-benefit analysis. An algorithm such as this one, based on the very limited efficacy and safety data available, may be viewed as setting priorities for a comprehensive research agenda, more than dictating rigid treatment guidelines. In closing, it can be suggested that future research on the pharmacotherapy of early-onset depressive disorder pay particular attention to the following three aspects: 1. Too many drugs, too few data: Rapid advances in drug development have led to a plethora of available antidepressant agents. It is clear that there are many more agents available than can be adequately studied at present. Because many such agents are mechanistically similar, if not identical, it may be wise to focus research efforts on truly novel agents, particularly those (such as the CRH receptor antagonists, or those affecting neurosteroidogenesis) whose action is based on preclinical and clinical pathophysiologic disease paradigms. 2. Longitudinal follow-up and maintenance studies: Essentially all reviewed treatment studies have been short-term trials. There is a marked paucity of longer-term follow-up data, or of naturalistic and "real-world" effectiveness studies. For example, one of the few studies addressing maintenance pharmacotherapy for early-onset depression has demonstrated surprisingly high recurrence rates, even for those subjects actively on maintenance medication. 3. Long-term safety: Clinicians and parents alike often face difficult decisions regarding the long-term exposure of antidepressant drugs on the developing brain. Although no definitive long-term safety data are likely to become available anytime soon, real risks, such as suicide, and potential sequelae of long-term exposure to the underlying illness itself need all to be part of any decision-making process. Preclinical studies have shown that brain-derived neurotrophic factor (BDNF) levels can be upregulated by antidepressants, and low BDNF factors have been associated with atrophic brain changes in recurrent forms of adult MDD. Although these observations require specific application to juvenile forms of the disorder, they raise the exciting prospect that the natural course of the illne
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PMID:Pharmacotherapy of early-onset depression. Update and new directions. 1067 94

Neurotrophins modulate synaptic transmission and plasticity in the adult brain. We here show a novel feature of this synaptic modulation, i.e. that two populations of excitatory synaptic connections to granule cells in the dentate gyrus, lateral perforant path (LPP) and medial perforant path (MPP), are differentially influenced by the neurotrophins BDNF and NT-3. Using field recordings and whole-cell patch-clamp recordings in hippocampal slices, we found that paired-pulse (PP) depression at MPP-granule cell synapses was impaired in BDNF knock-out (+/-) mice, but PP facilitation at LPP synapses to the same cells was not impaired. In accordance, scavenging of endogenous BDNF with TrkB-IgG fusion protein also impaired PP depression at MPP-granule cell synapses, but not PP facilitation at LPP-granule cell synapses. Conversely, in NT-3+/- mice, PP facilitation was impaired at LPP-granule cell synapses whilst PP depression at MPP-granule cell synapses was unaffected. These deficits could be reversed by application of exogenous neurotrophins in an afferent-specific manner. Our data suggest that BDNF and NT-3 differentially regulate the synaptic impact of different afferent inputs onto single target neurons in the CNS.
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PMID:Afferent-specific modulation of short-term synaptic plasticity by neurotrophins in dentate gyrus. 1071 46

Neuronal expression of brain-derived neurotrophic factor (BDNF) has been implicated in the mechanism of infarct tolerance (resistance to stroke) (H. Yanamoto et al., Infarct tolerance accompanied enhanced BDNF-like immunoreactivity in neuronal nuclei, submitted to Brain Res.), a process that takes more than 7 days following a preconditioning of repetitive cortical spreading depression (CSD). To investigate whether an elevated level of BDNF protein in the brain solely protects neurons against temporary focal ischemia, recombinant (r)BDNF was infused into the rat neocortex. Recombinant BDNF (or vehicle: saline) was administered into the left neocortex via an implanted osmotic minipump for 2.5, 7, 10 or 14 days pre-ischemia, during ischemia and for 2 days post-ischemia (8 microgram in total) in male Sprague-Dawley rats (n=6 each). Temporary focal ischemia was induced in the left middle cerebral artery (MCA) territory by three-vessel occlusion of bilateral common carotid arteries (CCAs) and MCA for 2 h, and the cerebral infarct volume was analyzed 2 days after ischemia using TTC staining. Regional cerebral blood flow (rCBF) of the left neocortex was monitored after 14 days of intracerebral administration of BDNF or vehicle (n=10 each). The distribution of BDNF following different periods of rBDNF or vehicle-infusion was analyzed using immunohistochemical techniques (n=5 each). In the groups treated with 8 microgram of rhBDNF for 7, 10, or 14 days pre-ischemia, there were significant reductions of neocortical infarct volume compared to in the control or vehicle-treated groups (p<0.05). In the rCBF study, there was no significant change after the infusion of 8 microgram rhBDNF for 14 days. In the histological study, a wide distribution of BDNF-like immunoreactivity in the neuronal nuclei in the ipsilateral neocortex was demonstrated after the infusion of 8 microgram rhBDNF for 14 days. The BDNF-like immunoreactivity in the neuronal nuclei was enhanced at the time that the resistance to stroke was achieved by direct intra-cerebral infusion of exogenous rBDNF. Elucidating the function of the BDNF-like protein located in the neuronal nuclei should reveal a new strategy for neuroprotection against ischemic brain attack in humans.
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PMID:Infarct tolerance induced by intra-cerebral infusion of recombinant brain-derived neurotrophic factor. 1071 70

1. To address questions of whether long-term depression (LTD) in the visual cortex is expressed in pre- or postsynaptic sites, whether brain-derived neurotrophic factor (BDNF) exerts its LTD-blocking action without involvement of GABAergic inhibition, and whether the action of BDNF is pre- or postsynaptic, we observed excitatory postsynaptic currents (EPSCs) from solitary neurones cultured on glial microislands. In this preparation GABAergic inhibition is not involved and a group of synapses (autapses) which generate evoked EPSCs is thought to be the same as those generating spontaneous EPSCs. 2. A short depolarising voltage step to the soma generated Na+ spikes which were followed by autaptic EPSCs. When this somatic activation was paired with prolonged depolarisation for 100 ms to -30 mV and repeated at 1 Hz for 5 min, LTD was induced in all of the nine cells tested. Then, the frequency of spontaneous EPSCs decreased, but the amplitude did not change, suggesting that the site of LTD expression is presynaptic. 3. Application of BDNF at 50 ng ml-1 blocked the depression of evoked EPSCs and the decrease in the frequency of spontaneous EPSCs. An inhibitor for receptor tyrosine kinases, K252a, antagonised the action of BDNF, suggesting an involvement of BDNF receptors, TrkB. 4. These results suggest that BDNF prevents low-frequency inputs from inducing LTD of excitatory synaptic transmission through presynaptic mechanisms in the developing visual cortex.
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PMID:Brain-derived neurotrophic factor blocks long-term depression in solitary neurones cultured from rat visual cortex. 1074 92


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