Behavioural brain research
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There is a clear link between dysregulation of glutamatergic signaling and mood disorders. Genetic variants in the glutamate receptor gene GRIK4, which encodes the kainate receptor subunit GluK4, alter the susceptibility for depression, bipolar disorder and schizophrenia. Here we demonstrate that Grik4(-/-) mice have reduced anxiety and an antidepressant-like phenotype. ⋯ Expression of the GluK4 receptor subunit in the forebrain is restricted to the CA3 region of the hippocampus and dentate gyrus regions where KARs are known to modulate synaptic plasticity. We tested whether Grik4 ablation had effects on mossy fiber (MF) plasticity and found there to be a significant impairment in LTP likely through a loss of KAR modulation of excitability of the presynaptic MF axons. These studies demonstrate a clear anxiolytic and antidepressant phenotype associated with ablation of Grik4 and a parallel disruption in hippocampal plasticity, providing support for the importance of this receptor subunit in mood disorders.
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The incidence of stress and stress-related disorders with the transition to motherhood, such as postpartum depression, is estimated to be 20%. Selective serotonin reuptake inhibitor (SSRI) medications are currently the antidepressant of choice to treat maternal mood disorders. However, little is known about the effects of these medications on the maternal brain and behavior. ⋯ In the absence of maternal stress, fluoxetine treatment alone significantly increased maternal arched-back nursing of pups, increased anxiety-related behavior, and decreased serum levels of corticosterone and corticosteroid binding globulin in the dam. This research provides important information on how SSRIs may act on the behavior, physiology, and neural plasticity of the mother. Although this is a first step in investigating the role of antidepressant treatment on the mother, much more work is needed before we can understand and improve the efficacy of these medications to treat mood disorders in pregnant and postpartum women.
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The G-protein coupled muscarinic acetylcholine receptors, widely expressed in the CNS, have been implicated in fragile X syndrome (FXS). Recent studies have reported an overactive signaling through the muscarinic receptors in the Fmr1KO mouse model. Hence, it was hypothesized that reducing muscarinic signaling might modulate behavioral phenotypes in the Fmr1KO mice. Pharmacological studies from our lab have provided evidence for this hypothesis, with subtype-preferring muscarinic M1 and M4 receptor antagonists modulating select behaviors in the Fmr1KO mice. Since the pharmacological antagonists were not highly specific, we investigated the specific role of M4 receptors in the Fmr1KO mouse model, using a genetic approach. ⋯ Reducing M4 receptor signaling altered only select behavioral phenotypes in the Fmr1KO mouse model, suggesting that other targets are involved in the modulation of fragile X behaviors.
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Bile duct ligation (BDL) induces primary biliary cirrhosis characterized by cholestasis, impaired liver function and cognition including impairment of memory formation and anxiety-like behaviors. Endogenous opioid and acetylcholine levels are elevated in animal model of cholestasis. In addition, there is no data about the effects of interaction opioidergic and cholinergic systems of dorsal hippocampus (CA1) on amnesia-induced by cholestasis. ⋯ Further, all cross co-administration ineffective doses of naloxone (0.0125 μg/mice), mecamylamine (0.125 μg/mice) and scopolamine (0.125 μg/mice) reversed cholestasis-induced amnesia. All doses of the drugs have no effect on exploratory behaviors. The data strongly revealed that synergistic effect between opioidergic and cholinergic systems of CA1 on the modulation of cholestasis-induced amnesia.
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Review
Cognitive side effects of cancer therapy demonstrate a functional role for adult neurogenesis.
Cancer therapies frequently result in a spectrum of neurocognitive deficits that include impaired learning, memory, attention and speed of information processing. Damage to dynamic neural progenitor cell populations in the brain are emerging as important etiologic factors. Radiation and chemotherapy-induced damage to neural progenitor populations responsible for adult hippocampal neurogenesis and for maintenance of subcortical white matter integrity are now believed to play major roles in the neurocognitive impairment many cancer survivors experience.