GBR 12909 administration as a mouse model of bipolar disorder mania: mimicking quantitative assessment of manic behavior

Mania is a core feature of bipolar disorder (BD) that traditionally is assessed using rating scales. Studies using a new human behavioral pattern monitor (BPM) recently demonstrated that manic BD patients exhibit a specific profile of behavior that differs from schizophrenia and is characterized by increased motor activity, increased specific exploration, and perseverative locomotor patterns as assessed by spatial d. It was hypothesized that disrupting dopaminergic homeostasis by inhibiting dopamine transporter (DAT) function would produce a BD mania-like phenotype in mice as assessed by the mouse BPM. We compared the spontaneous locomotor and exploratory behavior of C57BL/6J mice treated with the catecholamine transporter inhibitor amphetamine or the selective DAT inhibitor GBR 12909 in the mouse BPM. We also assessed the duration of the effect of GBR 12909 by testing mice in the BPM for 3 h and its potential strain dependency by testing 129/SvJ mice. Amphetamine produced hyperactivity and increased perseverative patterns of locomotion as reflected in reduced spatial d values but reduced exploratory activity in contrast to the increased exploration observed in BD patients. GBR 12909 increased activity and reduced spatial d in combination with increased exploratory behavior, irrespective of inbred strain. These effects persisted for at least 3 h. Thus, selectively inhibiting the DAT produced a long-lasting cross-strain behavioral profile in mice that was consistent with that observed in manic BD patients. These findings support the use of selective DAT inhibition in animal models of the impaired dopaminergic homeostasis putatively involved in the pathophysiology of BD mania

Differences in Spontaneously Avoiding or Approaching Mice Reflect Differences in CB1-Mediated Signaling of Dorsal Striatal Transmission

Approach or avoidance behaviors are accompanied by perceptual vigilance for, affective reactivity to and behavioral predisposition towards rewarding or punitive stimuli, respectively. We detected three subpopulations of C57BL/6J mice that responded with avoiding, balancing or approaching behaviors not induced by any experimental manipulation but spontaneously displayed in an approach/avoidance conflict task. Although the detailed neuronal mechanisms underlying the balancing between approach and avoidance are not fully clarified, there is growing evidence that endocannabinoid system (ECS) plays a critical role in the control of these balancing actions. The sensitivity of dorsal striatal synapses to the activation of cannabinoid CB1 receptors was investigated in the subpopulations of spontaneously avoiding, balancing or approaching mice. Avoiding animals displayed decreased control of CB1 receptors on GABAergic striatal transmission and in parallel increase of behavioral inhibition. Conversely, approaching animals exhibited increased control of CB1 receptors and in parallel increase of explorative behavior. Balancing animals reacted with balanced responses between approach and avoidance patterns. Treating avoiding animals with URB597 (fatty acid amide hydrolase inhibitor) or approaching animals with AM251 (CB1 receptor inverse agonist) reverted their respective behavioral and electrophysiological patterns. Therefore, enhanced or reduced CB1-mediated control on dorsal striatal transmission represents the synaptic hallmark of the approach or avoidance behavior, respectively. Thus, the opposite spontaneous responses to conflicting stimuli are modulated by a different involvement of endocannabinoid signaling of dorsal striatal neurons in the range of temperamental traits related to individual differences

Chronic alcohol remodels prefrontal neurons and disrupts NMDAR-mediated fear extinction encoding

Alcoholism is frequently co-morbid with post-traumatic stress disorder, but it is unclear how alcohol affects the neural circuits mediating recovery from trauma. We found that chronic intermittent ethanol (CIE) impaired fear extinction and remodeled the dendritic arbor of medial prefrontal cortical (mPFC) neurons in mice. CIE impaired extinction encoding by infralimbic mPFC neurons in vivo and functionally downregulated burst-mediating NMDA GluN1 receptors. These findings suggest that alcohol may increase risk for trauma-related anxiety disorders by disrupting mPFC-mediated extinction of fear

Abstinence following Alcohol Drinking Produces Depression-Like Behavior and Reduced Hippocampal Neurogenesis in Mice

Alcoholism and depression show high degrees of comorbidity. Clinical evidence also indicates that depression that emerges during abstinence from chronic alcohol use has a greater negative impact on relapse than pre-existing depression. Although no single neurobiological mechanism can account for the behavioral pathologies associated with these devastating disorders, converging evidence suggests that aspects of both alcoholism and depression are linked to reductions in hippocampal neurogenesis. Here, we report results from a novel preclinical behavioral model showing that abstinence from voluntary alcohol drinking leads to the emergence of depression-like behavior and reductions in neurogenesis. C57BL/6J mice were allowed to self-administer ethanol (10% v/v) vs H(2)O in the home cage for 28 days. Alcohol was then removed for 1 or 14 days, and mice were tested in the forced swim test to measure depression-like behavior. After 14 days, but not 1 day of abstinence from alcohol drinking, mice showed a significant increase in depression-like behavior. The significant increase in depression-like behavior during abstinence was associated with a reduction in proliferating cell nuclear antigen (PCNA) and doublecortin (DCX) immunoreactivity in the dentate gyrus of the hippocampus indicating that both the number of proliferating neural progenitor cells (NPC) and immature neurons were reduced, respectively. The number of NPCs that were labeled with bromo-deoxyuridine (BrdU) at the beginning of alcohol exposure was not altered indicating that survival of NPCs is not linked to abstinence-induced depression. Chronic treatment (14 days) with the antidepressant desipramine during abstinence prevented both the emergence of depression-like behavior and the reduction in hippocampal neurogenesis indicating that abstinence-induced depression is associated with structural plasticity in the hippocampus. Overall, the results of this study support the conclusion that profound functional (ie behavioral) and structural changes occur during abstinence from alcohol use and suggest that antidepressant treatment may alleviate some of these pathological neurobehavioral adaptations