Sex-specific developmental alterations in DYRK1A expression in the brain of a Down syndrome mouse model.

Aberrant neurodevelopment in Down syndrome (DS)-caused by triplication of human chromosome 21-is commonly attributed to gene dosage imbalance, linking overexpression of trisomic genes with disrupted developmental processes, with DYRK1A particularly implicated. We hypothesized that regional brain DYRK1A protein overexpression in trisomic mice varies over development in sex-specific patterns that may be distinct from Dyrk1a transcription, and reduction of Dyrk1a copy number from 3 to 2 in otherwise trisomic mice reduces DYRK1A, independent of other trisomic genes. DYRK1A overexpression varied with age, sex, and brain region, with peak overexpression on postnatal day (P) 6 in both sexes. Sex-dependent differences were also evident from P15-P24. Reducing Dyrk1a copy number confirmed that these differences depended on Dyrk1a gene dosage and not other trisomic genes. Trisomic Dyrk1a mRNA and protein expression were not highly correlated. Sex-specific patterns of DYRK1A overexpression during trisomic neurodevelopment may provide mechanistic targets for therapeutic intervention in DS.

Sexually dimorphic DYRK1A overexpression on postnatal day 15 in the Ts65Dn mouse model of Down syndrome: Effects of pharmacological targeting on behavioral phenotypes.

The neurotypical spatiotemporal patterns of gene expression are disrupted in Down syndrome (DS) by trisomy of human chromosome 21 (Hsa21), resulting in altered behavioral development and brain circuitry. The Ts65Dn DS mouse model exhibits similar phenotypes to individuals with DS due to three copies of approximately one-half of the genes found on Hsa21. Dual-specificity Tyrosine Phosphorylation-regulated Kinase 1a (Dyrk1a), one of these triplicated genes, is an attractive target to normalize brain development due to its influence in cellular brain deficits seen in DS. We hypothesized that postnatal development of DYRK1A expression is dysregulated in trisomic animals, and found significant overexpression of DYRK1A in the hippocampus, cerebral cortex, and cerebellum at postnatal day (P) 15 in male-but not female-Ts65Dn mice. We then hypothesized the existence of sex-dependent effects of trisomy on neurobehavioral attributes during P16-17, and that administration of a DYRK1A inhibitor (CX-4945, ~75 mg/kg) beginning on P14 would normalize aberrant behavior in trisomic animals. Both male and female trisomic mice given control injections of phosphate buffered saline (PBS) displayed sustained levels of locomotor activity over a 10-minute test in contrast to the PBS-treated euploid animals that showed significant within-session habituation. Trisomic animals were more persistent in choosing to remain in home shavings in a preference test. Treatment with CX-4945 failed to confirm therapeutic effects. CX-4945 prevented growth, and both CX-4945 and its 10% dimethyl sulfoxide vehicle affected locomotor activity in trisomic and euploid groups, indicating a non-specific disruption of behavior. Despite the negative outcomes for CX-4945, the novel demonstration of sexually dimorphic DYRK1A expression in trisomic animals at P15 supports the broader hypothesis that overexpression of trisomic genes in DS can vary with age, sex, and brain region. Identifying the developmental timing of periods of dysregulated DYRK1A may be important for understanding individual differences in neurodevelopmental trajectories in DS and for developing effective therapeutic interventions targeting DYRK1A.

A new Down syndrome rat model races forward.

Animal models of Down syndrome (DS) provide an essential resource for understanding genetic, cellular, and molecular contributions to traits associated with trisomy 21 (Ts21). Recent genetic enhancements in the development of DS models, including the new TcHSA21rat model (Kazuki et al.), have potential to transform our understanding of and potential therapies for Ts21.

The effects of gestational choline supplementation on cerebellar Purkinje cell number in the sheep model of binge alcohol exposure during the first trimester-equivalent.

Individuals with fetal alcohol spectrum disorders (FASD) incur enduring brain damage and neurodevelopmental impairments from prenatal alcohol exposure (PAE). Preclinical rodent models have demonstrated that choline supplementation during development can reduce the severity of adverse neurodevelopmental consequences of PAE. This study used the sheep model to evaluate dietary choline supplementation during pregnancy as a therapeutic intervention, testing the hypothesis that choline can ameliorate alcohol-induced cerebellar Purkinje cell loss. Pregnant ewes were randomly assigned either to a normal control [NC] group (n = 8), or to groups given intravenous infusions of alcohol (or saline) from gestational days 4-41 (the first trimester-equivalent). A weekly binge-drinking pattern was modeled, with three consecutive days of infusions of saline [SAL], 1.75 g/kg/day alcohol [1.75ALC], or 2.5 g/kg/day alcohol [2.5ALC] followed by four days off. Infused ewes were randomly assigned to receive dietary supplements throughout pregnancy of choline (10 mg/kg/day) or placebo (n = 8 per group). Mean blood alcohol concentrations (BAC) were significantly higher in the 2.5ALC groups (287 mg/dL) than the 1.75ALC groups (197 mg/dL). Lamb cerebella were harvested on postnatal day 180 and processed for stereological counts of Purkinje cells. Both alcohol doses caused significant reductions in Purkinje number relative to NC and SAL-Placebo groups, confirming previous findings. Effects of choline supplementation depended on infusion group: it significantly protected against Purkinje cell loss in the 2.5ALC group, had no effect in the 1.75ALC group, and significantly reduced numbers in the SAL-Choline group (though neither the SAL-Choline nor the SAL-Placebo group differed from the NC group). The protection by choline evident only in the 2.5ALC group suggests that multiple, BAC-dependent mechanisms of cerebellar damage may be activated with alcohol exposure in the first trimester, and that choline may protect against pathogenic mechanisms that emerge at higher BACs. These outcomes extend the evidence that early choline supplementation can mitigate some neurodevelopmental defects resulting from binge-like PAE.

Understanding ethanol's acute effects on medial prefrontal cortex neural activity using state-space approaches.

Acute ethanol (EtOH) intoxication results in several maladaptive behaviors that may be attributable, in part, to the effects of EtOH on neural activity in medial prefrontal cortex (mPFC). The acute effects of EtOH on mPFC function have been largely described as inhibitory. However, translating these observations on function into a mechanism capable of delineating acute EtOH's effects on behavior has proven difficult. This review highlights the role of acute EtOH on electrophysiological measurements of mPFC function and proposes that interpreting these changes through the lens of dynamical systems theory is critical to understand the mechanisms that mediate the effects of EtOH intoxication on behavior. Specifically, the present review posits that the effects of EtOH on mPFC N-methyl-d-aspartate (NMDA) receptors are critical for the expression of impaired behavior following EtOH consumption. This hypothesis is based on the observation that recurrent activity in cortical networks is supported by NMDA receptors, and, when disrupted, may lead to impairments in cognitive function. To evaluate this hypothesis, we discuss the representation of mPFC neural activity in low-dimensional, dynamic state spaces. This approach has proven useful for identifying the underlying computations necessary for the production of behavior. Ultimately, we hypothesize that EtOH-related alterations to NMDA receptor function produces alterations that can be effectively conceptualized as impairments in attractor dynamics and provides insight into how acute EtOH disrupts forms of cognition that rely on mPFC function. This article is part of the special Issue on 'Neurocircuitry Modulating Drug and Alcohol Abuse'.

Behavioral Phenotyping for Down Syndrome in Mice.

Down syndrome (DS) is the most frequent genetic cause of intellectual disability, characterized by alterations in different behavioral symptom domains: neurodevelopment, motor behavior, and cognition. As mouse models have the potential to generate data regarding the neurological basis for the specific behavioral profile of DS, and may indicate pharmacological treatments with the potential to affect their behavioral phenotype, it is important to be able to assess disease-relevant behavioral traits in animal models in order to provide biological plausibility to the potential findings. The field is at a juncture that requires assessments that may effectively translate the findings acquired in mouse models to humans with DS. In this article, behavioral tests are described that are relevant to the domains affected in DS. A neurodevelopmental behavioral screen, the balance beam test, and the Multivariate Concentric Square Field test to assess multiple behavioral phenotypes and locomotion are described, discussing the ways to merge these findings to more fully understand cognitive strengths and weaknesses in this population. New directions for approaches to cognitive assessment in mice and humans are discussed. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Preweaning neurodevelopmental battery Basic Protocol 2: Balance beam Basic Protocol 3: Multivariate concentric square field test (MCSF).

Evaluation of the therapeutic potential of Epigallocatechin-3-gallate (EGCG) via oral gavage in young adult Down syndrome mice.

Epigallocatechin-3-gallate (EGCG) is a candidate therapeutic for Down syndrome (DS) phenotypes based on in vitro inhibition of DYRK1A, a triplicated gene product of Trisomy 21 (Ts21). Consumption of green tea extracts containing EGCG improved some cognitive and behavioral outcomes in DS mouse models and in humans with Ts21. In contrast, treatment with pure EGCG in DS mouse models did not improve neurobehavioral phenotypes. This study tested the hypothesis that 200 mg/kg/day of pure EGCG, given via oral gavage, would improve neurobehavioral and skeletal phenotypes in the Ts65Dn DS mouse model. Serum EGCG levels post-gavage were significantly higher in trisomic mice than in euploid mice. Daily EGCG gavage treatments over three weeks resulted in growth deficits in both euploid and trisomic mice. Compared to vehicle treatment, EGCG did not significantly improve behavioral performance of Ts65Dn mice in the multivariate concentric square field, balance beam, or Morris water maze tasks, but reduced swimming speed. Furthermore, EGCG resulted in reduced cortical bone structure and strength in Ts65Dn mice. These outcomes failed to support the therapeutic potential of EGCG, and the deleterious effects on growth and skeletal phenotypes underscore the need for caution in high-dose EGCG supplements as an intervention in DS.

Influence of allelic differences in Down syndrome.

Both trisomic and non-trisomic genes may affect the incidence and severity of phenotypes associated with Down syndrome (DS). The importance of extra (trisomic) genetic material is emphasized in DS, with less emphasis to the allelic composition of candidate trisomic genes in defining the trisomic gene-phenotype relationship in DS. Allelic differences in non-trisomic genes have been shown to be important moderators of cardiac, leukemia, and developmental phenotypes associated with DS. Trisomic mouse models provide an in vivo genetic platform for examining the gene-phenotype relationship, including the influence of allelic variants, on DS-like phenotypes. DS mouse models have differing trisomic genetic makeup, and optimal development, viability and translational value of these mouse models may require a non-inbred genetic background with heterogeneity at many loci. Additionally, understanding the contribution of specific genes or regions to DS phenotypes often requires the utilization of genetically manipulated mice that may be established on a different inbred background than the trisomic mice. The impact of allelic differences of trisomic and background genes in human and model systems may offer insight into the variability in occurrence and severity of trisomic phenotypes.

Usage of and attitudes about green tea extract and Epigallocathechin-3-gallate (EGCG) as a therapy in individuals with Down syndrome.

OBJECTIVE: Usage of and views concerning alternative therapies in the DS community are not well documented. Some positive effects of green tea extracts (GTE) containing Epigallocathechin-3-gallate (EGCG) have been reported in individuals with DS and DS mouse models, but minimal improvements or detrimental effects of pure EGCG treatment have been reported in DS mouse models. Given the uncertainty about the effectiveness of these supplements, the goal of this study was to determine the relative prevalence of and attitudes about GTE/EGCG treatments among DS caregivers. METHODS: An anonymous survey about attitudes and usage of GTE/EGCG in individuals with DS was completed by caregivers of these individuals. RESULTS: GTE/EGCG treatment was provided by 18% of responding caregivers who were mostly younger, highly educated, and utilized scientific sources and other parents to influence their decision to use GTE/EGCG. Individuals with DS who received GTE/EGCG were characterized as less severely disabled. Most caregivers who did not give GTE/EGCG reported concerns about potential side effects and lack of effectiveness. Few caregivers consulted with medical providers about GTE/EGCG usage. CONCLUSIONS: These results demonstrate a need for communication between caregivers, medical providers, and scientists about potential benefits and risks for adverse effects of GTE, EGCG, and other nutritional supplements in individuals with DS.

Maternal choline supplementation mitigates alcohol-induced fetal cranio-facial abnormalities detected using an ultrasonographic examination in a sheep model.

Early detection of prenatal alcohol exposure is critical for designing and testing effectiveness of interventional therapeutics. Choline supplementation during and after prenatal alcohol exposure has shown promising benefits in improving outcomes in rodent models and clinical studies. A sheep model of first trimester-equivalent binge alcohol exposure was used in this study to model the dose of maternal choline supplementation used in an ongoing prospective clinical trial involving pregnancies at risk for FASD. Pregnant sheep were randomly assigned to six groups: Saline + Placebo control, Saline + Choline, binge Alcohol + Placebo (light binging), binge Alcohol + Choline, Heavy binge Alcohol + Placebo (heavy binging), and Heavy binge Alcohol + Choline. Ewes received intravenous alcohol or saline on three consecutive days per week from gestation day (GD) 4-41 to mimic a first trimester-equivalent weekend binge-drinking paradigm. Choline (10 mg/kg in the daily food ration) was administered from GD 4 until term. On GD 76, 11 fetal ultrasonographic measurements were collected transabdominally. Heavy binge alcohol exposure reduced fetal Frontothalamic Distance (FTD), Mean Orbital Diameter (MOD), and Mean Lens Diameter (MLD), and increased Interorbital Distance (IOD) and Thalamic Width (TW). Maternal choline supplementation mitigated most of these alcohol-induced effects. Maternal choline supplementation also improved overall fetal femur and humerus bone lengths, compared to their respective placebo groups. Taken together, these results indicate a potential dose-dependent effect that could impact the sensitivity of these ultrasonographic measures in predicting prenatal alcohol exposure. This is the first study in the sheep model to identify biomarkers of prenatal alcohol exposure in utero with ultrasound and co-administration of maternal choline supplementation.

Evidence for a Long-Lasting Compulsive Alcohol Seeking Phenotype in Rats.

Excessive drinking to intoxication is the major behavioral characteristic of those addicted to alcohol but it is not the only one. Indeed, individuals addicted to alcohol also crave alcoholic beverages and spend time and put much effort into compulsively seeking alcohol, before eventually drinking large amounts. Unlike this excessive drinking, for which treatments exist, compulsive alcohol seeking is therefore another key feature of the persistence of alcohol addiction since it leads to relapse and for which there are few effective treatments. Here we provide novel evidence for the existence in rats of an individual vulnerability to switch from controlled to compulsive, punishment-resistant alcohol seeking. Alcohol-preferring rats given access to alcohol under an intermittent 2-bottle choice procedure to establish their alcohol-preferring phenotype were subsequently trained instrumentally to seek and take alcohol on a chained schedule of reinforcement. When stable seeking-taking performance had been established, completion of cycles of seeking responses resulted unpredictably either in punishment (0.45 mA foot-shock) or the opportunity to make a taking response for access to alcohol. Compulsive alcohol seeking, maintained in the face of the risk of punishment, emerged in only a subset of rats with a predisposition to prefer and drink alcohol, and was maintained for almost a year. We show further that a selective and potent µ-opioid receptor antagonist (GSK1521498) reduced both alcohol seeking and alcohol intake in compulsive and non-compulsive rats, indicating its therapeutic potential to promote abstinence and prevent relapse in individuals addicted to alcohol.

Targeting trisomic treatments: optimizing Dyrk1a inhibition to improve Down syndrome deficits.

Overexpression of Dual-specificity tyrosine-phosphorylated regulated kinase 1A (DYRK1A), located on human chromosome 21, may alter molecular processes linked to developmental deficits in Down syndrome (DS). Trisomic DYRK1A is a rational therapeutic target, and although reductions in Dyrk1a genetic dosage have shown improvements in trisomic mouse models, attempts to reduce Dyrk1a activity by pharmacological mechanisms and correct these DS-associated phenotypes have been largely unsuccessful. Epigallocatechin-3-gallate (EGCG) inhibits DYRK1A activity in vitro and this action has been postulated to account for improvement of some DS-associated phenotypes that have been reported in preclinical studies and clinical trials. However, the beneficial effects of EGCG are inconsistent and there is no direct evidence that any observed improvement actually occurs through Dyrk1a inhibition. Inconclusive outcomes likely reflect a lack of knowledge about the tissue-specific patterns of spatial and temporal overexpression and elevated activity of Dyrk1a that may contribute to emerging DS traits during development. Emerging evidence indicates that Dyrk1a expression varies over the life span in DS mouse models, yet preclinical therapeutic treatments targeting Dyrk1a have largely not considered these developmental changes. Therapies intended to improve DS phenotypes through normalizing trisomic Dyrk1a need to optimize the timing and dose of treatment to match the spatiotemporal patterning of excessive Dyrk1a activity in relevant tissues. This will require more precise identification of developmental periods of vulnerability to enduring adverse effects of elevated Dyrk1a, representing the concurrence of increased Dyrk1a expression together with hypothesized tissue-specific-sensitive periods when Dyrk1a regulates cellular processes that shape the long-term functional properties of the tissue. Future efforts targeting inhibition of trisomic Dyrk1a should identify these putative spatiotemporally specific developmental sensitive periods and determine whether normalizing Dyrk1a activity then can lead to improved outcomes in DS phenotypes.

Epigallocatechin-3-gallate (EGCG) consumption in the Ts65Dn model of Down syndrome fails to improve behavioral deficits and is detrimental to skeletal phenotypes.

Down syndrome (DS) is caused by three copies of human chromosome 21 (Hsa21) and results in phenotypes including intellectual disability and skeletal deficits. Ts65Dn mice have three copies of ~50% of the genes homologous to Hsa21 and display phenotypes associated with DS, including cognitive deficits and skeletal abnormalities. DYRK1A is found in three copies in humans with Trisomy 21 and in Ts65Dn mice, and is involved in a number of critical pathways including neurological development and osteoclastogenesis. Epigallocatechin-3-gallate (EGCG), the main polyphenol in green tea, inhibits Dyrk1a activity. We have previously shown that EGCG treatment (~10mg/kg/day) improves skeletal abnormalities in Ts65Dn mice, yet the same dose, as well as ~20mg/kg/day did not rescue deficits in the Morris water maze spatial learning task (MWM), novel object recognition (NOR) or balance beam task (BB). In contrast, a recent study reported that an EGCG-containing supplement with a dose of 2-3mg per day (~40-60mg/kg/day) improved hippocampal-dependent task deficits in Ts65Dn mice. The current study investigated if an EGCG dosage similar to that study would yield similar improvements in either cognitive or skeletal deficits. Ts65Dn mice and euploid littermates were given EGCG [0.4mg/mL] or a water control, with treatments yielding average daily intakes of ~50mg/kg/day EGCG, and tested on the multivariate concentric square field (MCSF)-which assesses activity, exploratory behavior, risk assessment, risk taking, and shelter seeking-and NOR, BB, and MWM. EGCG treatment failed to improve cognitive deficits; EGCG also produced several detrimental effects on skeleton in both genotypes. In a refined HPLC-based assay, its first application in Ts65Dn mice, EGCG treatment significantly reduced kinase activity in femora but not in the cerebral cortex, cerebellum, or hippocampus. Counter to expectation, 9-week-old Ts65Dn mice exhibited a decrease in Dyrk1a protein levels in Western blot analysis in the cerebellum. The lack of beneficial therapeutic behavioral effects and potentially detrimental skeletal effects of EGCG found in Ts65Dn mice emphasize the importance of identifying dosages of EGCG that reliably improve DS phenotypes and linking those effects to actions of EGCG (or EGCG-containing supplements) in specific targets in brain and bone.

Maternal choline supplementation in a sheep model of first trimester binge alcohol fails to protect against brain volume reductions in peripubertal lambs.

Fetal alcohol spectrum disorder (FASD) is a leading potentially preventable birth defect. Poor nutrition may contribute to adverse developmental outcomes of prenatal alcohol exposure, and supplementation of essential micronutrients such as choline has shown benefit in rodent models. The sheep model of first-trimester binge alcohol exposure was used in this study to model the dose of maternal choline supplementation used in an ongoing prospective clinical trial involving pregnancies at risk for FASD. Primary outcome measures including volumetrics of the whole brain, cerebellum, and pituitary derived from magnetic resonance imaging (MRI) in 6-month-old lambs, testing the hypothesis that alcohol-exposed lambs would have brain volume reductions that would be ameliorated by maternal choline supplementation. Pregnant sheep were randomly assigned to one of five groups - heavy binge alcohol (HBA; 2.5 g/kg/treatment ethanol), heavy binge alcohol plus choline supplementation (HBC; 2.5 g/kg/treatment ethanol and 10 mg/kg/day choline), saline control (SC), saline control plus choline supplementation (SCC; 10 mg/kg/day choline), and normal control (NC). Ewes were given intravenous alcohol (HBA, HBC; mean peak BACs of ∼280 mg/dL) or saline (SC, SCC) on three consecutive days per week from gestation day (GD) 4-41; choline was administered on GD 4-148. MRI scans of lamb brains were performed postnatally on day 182. Lambs from both alcohol groups (with or without choline) showed significant reductions in total brain volume; cerebellar and pituitary volumes were not significantly affected. This is the first report of MRI-derived volumetric brain reductions in a sheep model of FASD following binge-like alcohol exposure during the first trimester. These results also indicate that maternal choline supplementation comparable to doses in human studies fails to prevent brain volume reductions typically induced by first-trimester binge alcohol exposure. Future analyses will assess behavioral outcomes along with regional brain and neurohistological measures.

Computed tomography assessment of peripubertal craniofacial morphology in a sheep model of binge alcohol drinking in the first trimester.

Identification of facial dysmorphology is essential for the diagnosis of fetal alcohol syndrome (FAS); however, most children with fetal alcohol spectrum disorders (FASD) do not meet the dysmorphology criterion. Additional objective indicators are needed to help identify the broader spectrum of children affected by prenatal alcohol exposure. Computed tomography (CT) was used in a sheep model of prenatal binge alcohol exposure to test the hypothesis that quantitative measures of craniofacial bone volumes and linear distances could identify alcohol-exposed lambs. Pregnant sheep were randomly assigned to four groups: heavy binge alcohol, 2.5 g/kg/day (HBA); binge alcohol, 1.75 g/kg/day (BA); saline control (SC); and normal control (NC). Intravenous alcohol (BA; HBA) or saline (SC) infusions were given three consecutive days per week from gestation day 4-41, and a CT scan was performed on postnatal day 182. The volumes of eight skull bones, cranial circumference, and 19 linear measures of the face and skull were compared among treatment groups. Lambs from both alcohol groups showed significant reduction in seven of the eight skull bones and total skull bone volume, as well as cranial circumference. Alcohol exposure also decreased four of the 19 craniofacial measures. Discriminant analysis showed that alcohol-exposed and control lambs could be classified with high accuracy based on total skull bone volume, frontal, parietal, or mandibular bone volumes, cranial circumference, or interorbital distance. Total skull volume was significantly more sensitive than cranial circumference in identifying the alcohol-exposed lambs when alcohol-exposed lambs were classified using the typical FAS diagnostic cutoff of ≤10th percentile. This first demonstration of the usefulness of CT-derived craniofacial measures in a sheep model of FASD following binge-like alcohol exposure during the first trimester suggests that volumetric measurement of cranial bones may be a novel biomarker for binge alcohol exposure during the first trimester to help identify non-dysmorphic children with FASD.

Low dose EGCG treatment beginning in adolescence does not improve cognitive impairment in a Down syndrome mouse model.

Down syndrome (DS) or Trisomy 21 causes intellectual disabilities in humans and the Ts65Dn DS mouse model is deficient in learning and memory tasks. DYRK1A is triplicated in DS and Ts65Dn mice. Ts65Dn mice were given up to ~20mg/kg/day epigallocatechin-3-gallate (EGCG), a Dyrk1a inhibitor, or water beginning on postnatal day 24 and continuing for three or seven weeks, and were tested on a series of behavioral and learning tasks, including a novel balance beam test. Ts65Dn as compared to control mice exhibited higher locomotor activity, impaired novel object recognition, impaired balance beam and decreased spatial learning and memory. Neither EGCG treatment improved performance of the Ts65Dn mice on these tasks. Ts65Dn mice had a non-significant increase in Dyrk1a activity in the hippocampus and cerebellum. Given the translational value of the Ts65Dn mouse model, further studies will be needed to identify the EGCG doses (and mechanisms) that may improve cognitive function.

Alcohol-Preferring Rats Show Goal Oriented Behaviour to Food Incentives but Are Neither Sign-Trackers Nor Impulsive.

Drug addiction is often associated with impulsivity and altered behavioural responses to both primary and conditioned rewards. Here we investigated whether selectively bred alcohol-preferring (P) and alcohol-nonpreferring (NP) rats show differential levels of impulsivity and conditioned behavioural responses to food incentives. P and NP rats were assessed for impulsivity in the 5-choice serial reaction time task (5-CSRTT), a widely used translational task in humans and other animals, as well as Pavlovian conditioned approach to measure sign- and goal-tracking behaviour. Drug-naïve P and NP rats showed similar levels of impulsivity on the 5-CSRTT, assessed by the number of premature, anticipatory responses, even when the waiting interval to respond was increased. However, unlike NP rats, P rats were faster to enter the food magazine and spent more time in this area. In addition, P rats showed higher levels of goal-tracking responses than NP rats, as measured by the number of magazine nose-pokes during the presentation of a food conditioned stimulus. By contrast, NP showed higher levels of sign-tracking behaviour than P rats. Following a 4-week exposure to intermittent alcohol we confirmed that P rats had a marked preference for, and consumed more alcohol than, NP rats, but were not more impulsive when re-tested in the 5-CSRTT. These findings indicate that high alcohol preferring and drinking P rats are neither intrinsically impulsive nor do they exhibit impulsivity after exposure to alcohol. However, P rats do show increased goal-directed behaviour to food incentives and this may be associated with their strong preference for alcohol.

The Novel µ-Opioid Receptor Antagonist GSK1521498 Decreases Both Alcohol Seeking and Drinking: Evidence from a New Preclinical Model of Alcohol Seeking.

Distinct environmental and conditioned stimuli influencing ethanol-associated appetitive and consummatory behaviors may jointly contribute to alcohol addiction. To develop an effective translational animal model that illuminates this interaction, daily seeking responses, maintained by alcohol-associated conditioned stimuli (CSs), need to be dissociated from alcohol drinking behavior. For this, we established a procedure whereby alcohol seeking maintained by alcohol-associated CSs is followed by a period during which rats have the opportunity to drink alcohol. This cue-controlled alcohol-seeking procedure was used to compare the effects of naltrexone and GSK1521498, a novel selective µ-opioid receptor antagonist, on both voluntary alcohol-intake and alcohol-seeking behaviors. Rederived alcohol-preferring, alcohol-nonpreferring, and high-alcohol-drinking replicate 1 line of rats (Indiana University) first received 18 sessions of 24 h home cage access to 10% alcohol and water under a 2-bottle choice procedure. They were trained subsequently to respond instrumentally for access to 15% alcohol under a second-order schedule of reinforcement, in which a prolonged period of alcohol-seeking behavior was maintained by contingent presentations of an alcohol-associated CS acting as a conditioned reinforcer. This seeking period was terminated by 20 min of free alcohol drinking access that achieved significant blood alcohol concentrations. The influence of pretreatment with either naltrexone (0.1-1-3 mg/kg) or GSK1521498 (0.1-1-3 mg/kg) before instrumental sessions was measured on both seeking and drinking behaviors, as well as on drinking in the 2-bottle choice procedure. Naltrexone and GSK1521498 dose-dependently reduced both cue-controlled alcohol seeking and alcohol intake in the instrumental context as well as alcohol intake in the choice procedure. However, GSK1521498 showed significantly greater effectiveness than naltrexone, supporting its potential use for promoting abstinence and preventing relapse in alcohol addiction.

Effects of one- and three-day binge alcohol exposure in neonatal C57BL/6 mice on spatial learning and memory in adolescence and adulthood.

Binge-like alcohol exposure during the early postnatal period in rats and mice causes deficits in spatial learning and memory that persist into adulthood. Wozniak et al. (2004) reported that heavy binge alcohol exposure on postnatal day 7 (PD 7) in C57BL/6 (B6) mice produced profound spatial learning deficits in the Morris water maze when tested in adolescence (P30-39); when tested in adulthood, however, the deficits were greatly attenuated. Using a similar PD 7 binge alcohol exposure paradigm in B6 mice, we tested whether a single-day (PD 7 only) alcohol treatment produced place learning deficits in both adolescence and in adulthood, and further tested whether a more extended (3-day, PD 7-9) alcohol exposure would induce more severe and enduring deficits. B6 mice were given either 2 subcutaneous injections of alcohol (2.5 g/kg each) 2 h apart on PD 7 or on PD 7-9, and compared with controls that received saline vehicle injections and controls that received no injections. The alcohol injections on PD 7 produced average peak blood alcohol concentrations of 472 mg/dL and evoked typical patterns of activated caspase-3-positive neurons in the cortex, hippocampal formation, and striatum 6 h after the last injection. Mice were given standard place training or random location training in the Morris water maze either as adolescents (PD 30-39) or adults (PD 70-79). The adolescents acquired the place learning more slowly than adults, and the alcohol treatments produced only modest place acquisition deficits. In contrast, both the PD7 and the PD 7-9 alcohol treatments resulted in large and significant spatial learning impairments in adults. In contrast to the previous findings of Wozniak et al. (2004), these results indicate that binge alcohol exposure in the 3rd trimester equivalent produces significant and enduring deficits in spatial learning in B6 mice.