Maternal separation stress reduced prenatal-ethanol-induced increase in exploratory behaviour and extracellular signal-regulated kinase activity.

In an attempt to better represent the aetiology of fetal alcohol spectrum disorder (FASD) and the associated psychological deficits, prenatal-ethanol exposure was followed by maternal separation in a rat model in order to account for the effects of early-life adversities in addition to in utero alcohol exposure. Extracellular signal-regulated kinase 1/2 (ERK1/2) and glycogen synthase kinase 3-ß (GSK3ß) are converging points for many signalling cascades and have been implicated in models of FASD and models of early-life stress. Therefore, these kinases may also contribute to the behavioural changes observed after the combination of both developmental insults. In this study, ethanol-dams voluntarily consumed a 0.066% saccharin-sweetened 10% ethanol (EtOH) solution for 10 days prior to pregnancy and throughout gestation while control-dams had ad libitumaccess to a 0.066% saccharin (sacc) solution. Whole litters were randomly assigned to undergo maternal separation (MS) for 3 h/day from P2 to P14 while the remaining litters were left undisturbed (nMS). This resulted in 4 experimental groups: control (sacc + nMS), MS (sacc + MS), EtOH (EtOH + nMS) and EtOH + MS. Throughout development, EtOH-rats weighed less than control rats. However, subsequent maternal separation stress caused EtOH + MS-rats to weigh more than EtOH-rats. In adulthood both MS- and EtOH-rats were hyperactive but the combination produced activity levels similar to that of control rats. All treated animals (MS-, EtOH- and EtOH + MS-rats) demonstrated a negative affective state shown by increased number and duration of 22 kHz ultrasonic vocalizations compared to control rats. Prenatal-ethanol exposure increased the P-GSK3ß/GSK3ß ratio in the prefrontal cortex (PFC) and maternal separation decreased the P-GSK3ß/GSK3ß ratio in the dorsal hippocampus (DH) of adult rats. However, maternal separation stress decreased the effect of prenatal-ethanol exposure on the P-ERK/ERK ratio in the PFC and DH and reduced prenatal-ethanol-induced hyperactivity. Therefore, indicating a significant interaction between prenatal-ethanol exposure and early-life stress on behaviour and the brain and may implicate P-ERK1/2 signalling in exploratory behaviour.

Early-Ethanol Exposure Induced Region-Specific Changes in Metabolic Proteins in the Rat Brain: A Proteomics Study.

In utero exposure to alcohol has been shown to cause a spectrum of cognitive and behavioral deficits. This study aimed to explore the long-term effects of early-ethanol exposure on proteins in the brain. Male Sprague-Dawley rat pups were exposed to 12% ethanol (4 g/kg/day i.p.) or volume-controlled saline during the third human trimester equivalent (P4-P9). At P31, prefrontal cortex (PFC) and dorsal hippocampus (DH) proteins were analyzed by isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography mass spectrometry (LC-MS). Early-ethanol exposure increased the capacity for metabolism of NADH and oxidative phosphorylation, as shown by an upregulation of NADH dehydrogenase (ubiquinone, 1 alpha subcomplex 9) while simultaneously decreasing the capacity to protect against oxidative stress in the PFC. Early-ethanol exposure decreased the capacity for ATP synthesis (> 2-fold down regulation of ATP synthase) and increased glycogen synthesis in the DH (> 2-fold decrease in glycogen synthase kinase-3ß). The effects of early-ethanol exposure on glucose metabolism and ATP production appeared to be region specific. In addition, early-ethanol exposure decreased structural proteins in both the PFC and DH. A greater number of proteins were altered in the DH than in the PFC, indicating that the DH may be more susceptible to the effects of early-ethanol exposure. These proteomic profiles provide valuable insight into the long-term molecular changes in the brain induced by early-ethanol exposure.

Early ethanol exposure and vinpocetine treatment alter learning- and memory-related proteins in the rat hippocampus and prefrontal cortex.

This study investigates the effects of early exposure to ethanol on cognitive function and neural plasticity-related proteins in the rat brain. Sprague-Dawley rats were administered 12% ethanol solution (4 g/kg/day i.p.) or saline from P4 to P9. Vinpocetine, a phosphodiesterase type 1 inhibitor, was tested to determine whether it could reverse any changes induced by early ethanol exposure. Hence, from P25 to P31, ethanol-exposed male rats were injected with vinpocetine (20 mg/kg/day i.p.) or vehicle (DMSO) prior to undergoing behavioral testing in the open field and Morris water maze (MWM) tests. Ethanol exposure did not adversely affect spatial memory in the MWM. A key finding in this study was a significant ethanol-induced change in the function of the phosphorylated extracellular signal-related kinase (P-ERK) signaling pathway in the prefrontal cortex (PFC) and dorsal hippocampus (DH) of rats that did not display overt behavioral deficits. The P-ERK/ERK ratio was decreased in the PFC and increased in the DH of ethanol-exposed rats compared with controls. Rats that received vinpocetine in addition to ethanol did not display any behavioral changes but did show alterations in neural plasticity-related proteins. Mitogen-activated protein kinase phosphatase was increased, whereas brain-derived neurotrophic factor was decreased, in the PFC of vinpocetine-treated ethanol-exposed rats, and phosphorylated-glycogen synthase kinase ß and synaptophysin were increased in the DH of these rats. This study provides insight into the long-term effects of early ethanol exposure and its interaction with vinpocetine in the rat brain. © 2016 Wiley Periodicals, Inc.

Developmental stress elicits preference for methamphetamine in the spontaneously hypertensive rat model of attention-deficit/hyperactivity disorder.

BACKGROUND: Developmental stress has been hypothesised to interact with genetic predisposition to increase the risk of developing substance use disorders. Here we have investigated the effects of maternal separation-induced developmental stress using a behavioural proxy of methamphetamine preference in an animal model of attention-deficit/hyperactivity disorder, the spontaneously hypertensive rat, versus Wistar Kyoto and Sprague-Dawley comparator strains. RESULTS: Analysis of results obtained using a conditioned place preference paradigm revealed a significant strain × stress interaction with maternal separation inducing preference for the methamphetamine-associated compartment in spontaneously hypertensive rats. Maternal separation increased behavioural sensitization to the locomotor-stimulatory effects of methamphetamine in both spontaneously hypertensive and Sprague-Dawley strains but not in Wistar Kyoto rats. CONCLUSIONS: Our findings indicate that developmental stress in a genetic rat model of attention-deficit/hyperactivity disorder may foster a vulnerability to the development of substance use disorders.

Genetic predisposition and early life experience interact to determine glutamate transporter (GLT1) and solute carrier family 12 member 5 (KCC2) levels in rat hippocampus.

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common child psychiatric disorders. While it is typically treated with medications that target dopamine and norepinephrine transmission, there is increasing evidence that other neurotransmitter systems, such as glutamate and GABA, may be involved. The aetiology of ADHD is unknown; however, there is evidence that early life stress may contribute to the development of the disorder. In the present study we used proteomic analysis (iTRAQ) followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blot analysis to investigate hippocampal protein profiles of three rat strains: an animal model of ADHD, spontaneously hypertensive rats (SHR), their control Wistar-Kyoto rats (WKY), and Sprague-Dawley rats (SD). We additionally investigated how these protein profiles are affected by maternal separation, a model of early life stress. Our findings show that solute carrier family 12 member 5 (KCC2) is increased in SHR hippocampus. The glutamate transporter GLT1 splice variant, GLT1b, was increased (proteomic analysis) while total GLT1 (comprised mostly of GLT1a splice variant) was reduced (Western blot analysis) in SHR hippocampus, compared to WKY and SD--a pattern that is consistent with elevated extracellular glutamate levels. Maternal separation increased total GLT1 in hippocampi of SHR, WKY, and SD, and reduced GLT1b in SHR hippocampus. Together these findings provide evidence for disturbed glutamatergic and GABAergic transmission in SHR hippocampus, maternal separation effects on glutamate uptake in hippocampi of all three strains, as well a unique effect of maternal separation on GLT1b levels in SHR hippocampus. These data suggest significant involvement of glutamatergic and GABAergic transmission in the neuropathophysiology of ADHD, and implicates changes in glutamatergic transmission as a result of early life stress.

Impaired Energy Metabolism and Disturbed Dopamine and Glutamate Signalling in the Striatum and Prefrontal Cortex of the Spontaneously Hypertensive Rat Model of Attention-Deficit Hyperactivity Disorder.

Attention deficit hyperactivity disorder (ADHD) is a heterogeneous behavioural disorder that affects 3-15 % of children worldwide. Spontaneously hypertensive rats (SHR) display the major symptoms of ADHD (hyperactivity, impulsivity and poor performance in tasks that require sustained attention) and are widely used to model the disorder. The present study aimed to test the hypothesis that SHR have a diminished capacity to generate ATP required for rapid synchronized neuronal firing, failure of which might lead to disturbances in neurotransmission that could contribute to their ADHD-like behaviour. Duplicate pooled (n = 5) samples of prefrontal cortex and striatum of prepubertal (35-day-old) SHR and Wistar Kyoto (WKY) rats were subjected to iTRAQ labeling and matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS). The MS/MS spectra were analyzed with ProteinPilot using the Ratus ratus database. Proteins detected with >95 % confidence were tested. SHR had decreased levels of several proteins involved in energy metabolism, cytoskeletal structure, myelination and neurotransmitter function when compared to WKY. Differences in protein levels between SHR and WKY were similar in prefrontal cortex and striatum, suggesting global changes in cortico-striato-thalamo-cortical circuits.

Proteomic analysis of maternal separation-induced striatal changes in a rat model of ADHD: The spontaneously hypertensive rat.

BACKGROUND: Developmental stress increases the risk of developing psychological disturbances and is modelled in rodents by maternal separation (MS). Attention-deficit/hyperactivity disorder (ADHD) is characterised by inattention, hyperactivity and impulsivity and is studied using the spontaneously hypertensive rat (SHR). Previous studies suggested that SHR differ from their progenitor strain, the Wistar-Kyoto (WKY), in their response to developmental stress. This study sought to investigate the effects of MS on striatal protein expression, a brain area implicated in the pathophysiology of ADHD and susceptible to developmental stress, in SHR, WKY and Sprague-Dawley (SD) rat strains. METHOD: Dissected striata of separated and non-separated SHR, WKY and SD (n = 6 per group) were assessed for MS-induced changes in protein expression using isobaric tagging (iTRAQ) and peptide quantification via matrix-assisted laser desorption/ionisation (MALDI) tandem mass spectrometry. RESULTS: Strain and MS-induced differences were observed in proteins related to energy metabolism, neuroprotection, protein folding, protein metabolism, signalling and structure. Striatal SHR protein levels were consistent with delayed neuronal maturation and altered neurotransmission and energy metabolism. MS produced mostly opposite effects on SHR striatal proteins compared to WKY and SD. COMPARISON WITH EXISTING METHODS: Proteomic profiling of protein expression in selected brain areas provides an assessment of overall changes in metabolic pathways that cannot be determined using standard protein isolation techniques. Furthermore, MS-induced changes in protein expression in the striatum of SHR, WKY and SD have not been reported. CONCLUSIONS: The results suggest that energy metabolism, neurotransmission and neural development are altered in SHR striatum and that WKY and SD are suitable comparator strains for SHR. The strain-dependent effects of MS on striatal protein expression reinforce the importance of gene × environment interactions in determining behavioural outcome.

The interaction between stress and exercise, and its impact on brain function.

In response to acute adversity, emotional signals shift the body into a state that permits rapid detection, identification, and appropriate response to a potential threat. The stress response involves the release of a variety of substances, including neurotransmitters, neurotrophic factors, hormones, and cytokines, that enable the body to deal with the challenges of daily life. The subsequent activation of various physiological systems can be both protective and damaging to the individual, depending on timing, intensity, and duration of the stressor. Successful recovery from stressful challenges during early life leads to strengthening of synaptic connections in health-promoting neural networks and reduced vulnerability to subsequent stressors that can be protective in later life. In contrast, chronic intense uncontrollable stress can be pathogenic and lead to disorders such as depression, anxiety, hypertension, Alzheimer's disease, Parkinson's disease, and an increased toxic response to additional stressors such as traumatic brain injury and stroke. This review briefly explores the interaction between stress experienced at different stages of development and exercise later in life.