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The effects of brain serotonin deficiency on behavioural disinhibition and anxiety-like behaviour following mild early life stress.

ABSTRACT: Aberrant serotonin (5-HT) signalling and exposure to early life stress have both been suggested to play a role in anxiety- and impulsivity-related behaviours. However, whether congenital 5-HT deficiency × early life stress interactions influence the development of anxiety- or impulsivity-like behaviour has not been established. Here, we examined the effects of early life maternal separation (MS) stress on anxiety-like behaviour and behavioural disinhibition, a type of impulsivity-like behaviour, in wild-type (WT) and tryptophan hydroxylase 2 (Tph2) knock-in (Tph2KI) mice, which exhibit ~60-80% reductions in the levels of brain 5-HT due to a R439H mutation in Tph2. We also investigated the effects of 5-HT deficiency and early life stress on adult hippocampal neurogenesis, plasma corticosterone levels and several signal transduction pathways in the amygdala. We demonstrate that MS slightly increases anxiety-like behaviour in WT mice and induces behavioural disinhibition in Tph2KI animals. We also demonstrate that MS leads to a slight decrease in cell proliferation within the hippocampus and potentiates corticosterone responses to acute stress, but these effects are not affected by brain 5-HT deficiency. However, we show that 5-HT deficiency leads to significant alterations in SGK-1 and GSK3? signalling and NMDA receptor expression in the amygdala in response to MS. Together, these findings support a potential role for 5-HT-dependent signalling in the amygdala in regulating the long-term effects of early life stress on anxiety-like behaviour and behavioural disinhibition.

SUBMITTER: Sachs BD

PROVIDER: S-EPMC3931011 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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The effects of brain serotonin deficiency on behavioural disinhibition and anxiety-like behaviour following mild early life stress.

Sachs Benjamin D BD Rodriguiz Ramona M RM Siesser William B WB Kenan Alexander A Royer Elizabeth L EL Jacobsen Jacob P R JP Wetsel William C WC Caron Marc G MG

The international journal of neuropsychopharmacology 20130514 9

Aberrant serotonin (5-HT) signalling and exposure to early life stress have both been suggested to play a role in anxiety- and impulsivity-related behaviours. However, whether congenital 5-HT deficiency × early life stress interactions influence the development of anxiety- or impulsivity-like behaviour has not been established. Here, we examined the effects of early life maternal separation (MS) stress on anxiety-like behaviour and behavioural disinhibition, a type of impulsivity-like behaviour, ...[more]

PMID: 23672796

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Project description:Low-level blast exposure can result in neurological impairment for military personnel. Currently, there is a lack of experimental data using sex as a biological variable in neurovascular outcomes following blast exposure. To model mild blast traumatic brain injury (mbTBI), male and female rats were exposed to a single 11 psi static peak overpressure blast wave using the McMillan blast device and cohorts were then euthanized at 6 h, 24 h, 7 d and 14 d post-blast followed by isolation of the amygdala. After mbTBI, animals experience immediate bradycardia, although no changes in oxygen saturation levels or weight loss are observed. Male mbTBI animals displayed significantly higher levels of anxiety-like behavior (open field and elevated plus maze) compared to male sham groups; however, there was no anxiety phenotype in female mbTBI animals. Blast-induced neurovascular damage was explored by measuring expression of tight junction (TJ) proteins (zonula occludens-1 (ZO-1), occludin and claudin-5), glial fibrillary acidic protein (GFAP) and astrocyte end-feet coverage around the blood-brain barrier (BBB). Western blot analysis demonstrates that TJ protein levels were significantly decreased at 6 h and 24 h post-mbTBI in male rats, but not in female rats, compared to sham. Female animals have decreased GFAP at 6 h post-mbTBI while male animals display decreased GFAP expression at 24 h post-mbTBI. By 7 d post-mbTBI, there were no significant differences in TJ or GFAP levels between groups in either sex. At 24 h post-mbTBI, vascular integrity and astrocytic end-feet coverage around the BBB was significantly decreased in males following mbTBI. These results demonstrate that loss of GFAP expression may be due to astrocytic damage at the BBB. Our findings also demonstrate sex differences in acute vascular and behavioral outcomes after single mbTBI. Female animals display a lack of BBB pathology after mbTBI corresponding to improved acute neuropsychological outcomes as compared to male animals.

Project description:BackgroundEvidence regarding longer-term psychiatric, psychological, and behavioural outcomes (for example, anxiety, mood disorders, depression, and attention disorders) following mild traumatic brain injury (mTBI) in children and adolescents has not been previously synthesized.ObjectiveTo conduct a systematic review of the available evidence examining psychiatric, psychological, and behavioural outcomes following mTBI in children and adolescents.Materials and methodsNine electronic databases were systematically searched from 1980 to August 2014. Studies selected met the following criteria: original data; study design was a randomized controlled trial, quasi-experimental design, cohort or historical cohort study, case-control study, or cross-sectional study; exposure included mTBI (including concussion); population included children and adolescents (<19 years) at the time of mTBI, as well as a comparison group (for example, healthy children, children with orthopaedic injuries); and included psychiatric, psychological, or behavioural outcomes (for example, anxiety, mood disorders, depression, attention disorders). Two authors independently assessed the quality and level of evidence with the Downs and Black (DB) criteria and Oxford Centre of Evidence-Based Medicine (OCEBM) model, respectively, for each manuscript.ResultsOf 9472 studies identified in the initial search, 30 were included and scored. Heterogeneity in methodology and injury definition precluded meta-analyses. The median methodological quality for all 30 studies, based on the DB criteria, was 15/33 (range 6 to 19). The highest level of evidence demonstrated by all reviewed studies was level 2b based on OCEBM criteria, with the majority (28/30 studies) classified at this level. Based on the literature included in this systematic review, psychological and psychiatric problems in children with a history of mTBI were found to be more prevalent when mTBI is associated with hospitalization, when assessment occurs earlier in the recovery period (that is, resolves over time), when there are multiple previous mTBIs, in individuals with preexisting psychiatric illness, when outcomes are based on retrospective recall, and when the comparison group is noninjured healthy children (as opposed to children with injuries not involving the head).ConclusionsOverall, few rigorous prospective studies have examined psychological, behavioural, and psychiatric outcomes following mTBI. In the absence of true reports of preinjury problems and when ideally comparing mild TBI to non-TBI injured controls, there is little evidence to suggest that psychological, behavioural, and/or psychiatric problems persist beyond the acute and subacute period following an mTBI in children and adolescents.

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The effects of brain serotonin deficiency on behavioural disinhibition and anxiety-like behaviour following mild early life stress.

Publications

The effects of brain serotonin deficiency on behavioural disinhibition and anxiety-like behaviour following mild early life stress.

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