The anxiolytic buspirone shifts coping strategy in novel environmental context of mice with different anxious phenotype

Higher exploratory and vigilant behaviors related to higher central dopaminergic activities of Formosan wood mice (Apodemus semotus) in light-dark exploration tests

Formosan wood mice (Apodemus semotus) are endemic rodents in Taiwan. Recently Formosan wood mice exhibit similar locomotor behaviors in the laboratory environment as in the field environment has shown. Contemporaneously, Formosan wood mice have higher moving distances of and central dopaminergic (DAergic) activities than C57BL/6 mice in behavioral test. This study tried to compare the behavioral responses between male Formosan wood mice and male C57BL/6 mice in the light-dark exploration tests. We also measured the levels of DA and 3,4-dihydroxyphenylacetic acid (DOPAC), the primary metabolite of DA, to assess the dopaminergic activity of the medial prefrontal cortex, striatum, and nucleus accumbens. Our data show that Formosan wood mice revealed higher exploration and central DAergic activities than did C57BL/6 mice in the light-dark exploration tests, and diazepam (an anxiolytics) treatment reduced the exploratory activity and central dopaminergic activities in Formosan wood mice, but not in C57BL/6 mice. After repeated exposure to light-dark exploration tests, the latency to dark zone was increased, and the duration in light zone as well as the central DAergic activity were decreased in C57BL/6 mice. This study provides comparative findings; Formosan wood mice showed the higher exploratory activities than C57BL/6 mice did, and their central DAergic activities were related to the behavioral responses in these two mice. This could potentially shed light on the reasons behind the prevalence of higher exploration and central dopaminergic activities. Using Formosan wood mice as a model to study human diseases related to hyperactivity adds significant value to the potential research.

Cognitive Test Solution in Mice with Different Brain Weights after Atomoxetine

In this paper, the data are presented concerning different reactions to seven daily injections of atomoxetine in two mouse strains differing in relative brain weight. Atomoxetine affected the performance in a puzzle-box cognitive test in a complicated way-the large brain mice were less successful at task solutions (presumably because they were not afraid of the brightly lit test box), while the small brain strain of atomoxetine treated mice solved the task more successfully. The behavior of all atomoxetine treated animals was more active in an aversive situation (an unescapable slippery funnel, (analogous to the Porsolt test) and the time of immobility decreased significantly in all atomoxetine treated mice. The general patterns of behavioral reactions to atomoxetine in the cognitive test and other interstrain differences demonstrated in these experiments made it possible to suggest that differences in ascending noradrenergic projections between the two strains used exist. Further analysis of the noradrenergic system in these strains is needed (and further analysis of the effects of drugs which affect noradrenergic receptors).

Memory reactivation mediates emotional valence updating of contextual memory in mice with protracted morphine withdrawal

Mice subjected to morphine locomotor sensitization develop increased anxiety-behavior expression during protracted morphine withdrawal. This behavioral change is dependent on reexposure to the context of locomotor sensitization and reflects a state of conditioned anxiety. In this study, the effect of memory reconsolidation on the expression of conditioned anxiety in mice with protracted morphine withdrawal was examined. Five experimental protocols involving male C57BL/6 mice were used in which the animals were subjected to locomotor sensitization induced by morphine and reexposed to the context associated with the drug effect 28 days after locomotor sensitization and immediately after subjected to elevated plus maze. In experiment 1, mice were subjected or not to memory reactivation session and was observed that memory reactivation 27 days after sensitization reduced conditioned anxiety. In experiment 2, mice were subjected to memory reactivation, 24 h, 6 h or 1 h before contextual reexposure, and the effect of memory reactivation coincided with the temporal requirement for reconsolidation. In experiment 3, which involved exposure to a situation of acute stress immediately before memory reactivation, the mice demonstrated a return to increased conditioned anxiety. To confirm the influence of reconsolidation, in experiments 4 and 5, mice subjected to memory reactivation were treated with Nimodipine, diazepam or cyclohexamine, substances commonly used as pharmacological controls in reconsolidation experiments. Treatment with each substance separately inhibited the effect of reactivation in experiment 5 (presence of acute stressor) but not in experiment 4 (absence of acute stressor). These results suggest that, in our experimental model, reconsolidation is mediated through updating of the emotional valence of contextual memory associated with the administration of morphine.

Anxiety-like behavior in acute and protracted withdrawal after morphine-induced locomotor sensitization in C57BL/6 male mice: The role of context

Contextual memory plays an important role in development and maintenance of drug addiction. However, little is known about of the role contextual memory in the emergence of a negative emotional state in the withdrawal period. Therefore, this study investigated anxiety-like behavior in acute and protracted morphine withdrawal of mice submitted to a locomotor sensitization protocol and the influence of contextual memory on this behavior. Male adult C57Bl6 mice were subjected to morphine locomotor sensitization and anxiety-like behavior was assessed by using the elevated plus maze test (EPM). To evaluate associative memory, the mice were re-exposed to the context of locomotor sensitization immediately before EPM. As expected, repeated morphine administrations promoted locomotor sensitization, seen as a gradual increase in the distance traveled during the acquisition phase. There was an increase in anxiety-like behavior upon acute withdrawal, as indicated by a decrease in open arms activity (OAA), but this effect dissipated over time. However, when the context was presented, mice in protracted withdrawal showed enhanced anxiety-like behavior, indicated by an increase in closed arms activity (CAA). This effect was context specific since re-exposure in an alternative context did not change the anxiety-like behavior. Treatment with diazepam counteracted the decrease in OAA in acute withdrawal and the increase in CAA induced by context re- exposure during protracted abstinence. Thus, repeated morphine administration induced a negative emotional state when the drug was discontinued. The context associated with drug exposure played a pivotal role in the appearance of anxiety-like behavior, even long after drug discontinuation. There were differences in the patterns of anxiety behaviors in acute (unconditioned anxiety-like behavior) and protracted (conditioned anxiety-like behavior) withdrawal since the former was characterized by a passive behavioral strategy and the latter by an active behavioral strategy.

Behavioral effects of buspirone in a mouse model of posttraumatic stress disorder

Buspirone presents a unique profile of action, which involves activation of 5-HT_1A receptors and complex effects on D₂-like dopaminergic receptors. This medication is studied in terms of potential clinical repositioning to conditions that are associated with dopaminergic dysfunctions including schizophrenia and substance use disorder. Buspirone antagonizes D₃ and D₄ receptors, however, depending on the dose it differentially interacts with D₂ receptors. Previously, we reported that some of D₂/D₃ dopaminergic agonists attenuate PTSD-like behavioral symptoms in mice. Here we investigated whether buspirone could also affect PTSD-like symptoms. We used the single prolonged stress (mSPS) protocol to induce PTSD-like behavior in adult male CD-1 mice. Buspirone (0.5, 2, or 10 mg/kg, i.p.) was injected for 15 consecutive days. The subjects were repeatedly examined in a variety of behavioral tests measuring conditioned freezing response, antidepressant-like effects, anxiety, and ultrasonic vocal response to the restraint stress. Mouse SPS resulted in prolonged immobility in the forced swim test and freezing in the fear-conditioning test, and produced symptoms of anxiety. Buspirone dose-dependently decreased the exaggerated freezing response in mice, but only at the dose of 2 mg/kg exhibited the anxiolytic-like effect in the elevated plus maze test. Buspirone reduced the number of ultrasonic calls in mSPS-exposed mice but revealed no antidepressant-like effect in the forced swim test. Present data suggest some positive effects of buspirone in the treatment of selected PTSD-like symptoms and prompt for its further clinical evaluation.

Plasma phospholipid profiling of a mouse model of anxiety disorder by hydrophilic interaction liquid chromatography coupled to high-resolution mass spectrometry

Glycerophospholipids (PLs), as amphipathic small molecules and the main constituents of biological membranes, play an important role in several cellular processes, even though their accurate identification from complex biological samples remains a challenge. In this paper, we report a fast and comprehensive HILIC-ESI-MS method for the analysis of glycerophospholipid classes using high-resolution mass spectrometry in negative mode. The final method enabled the quantitative analysis of 130 endogenous PL species in mouse plasma. The application of the method developed was to find differences of plasma PL composition in a mouse model of anxiety disorder. In the case of four PL classes and 35 PL species, significant differences were observed comparing low anxiety-related behavior with high anxiety-related behavior groups. The most characteristic trend was up-regulation in both the PL classes and PL species, and decreases were only detected in two phosphatidylcholines among 35 species in mice having elevated anxiety.

An Exploration Based Cognitive Bias Test for Mice: Effects of Handling Method and Stereotypic Behaviour

Behavioural tests to assess affective states are widely used in human research and have recently been extended to animals. These tests assume that affective state influences cognitive processing, and that animals in a negative affective state interpret ambiguous information as expecting a negative outcome (displaying a negative cognitive bias). Most of these tests however, require long discrimination training. The aim of the study was to validate an exploration based cognitive bias test, using two different handling methods, as previous studies have shown that standard tail handling of mice increases physiological and behavioural measures of anxiety compared to cupped handling. Therefore, we hypothesised that tail handled mice would display a negative cognitive bias. We handled 28 female CD-1 mice for 16 weeks using either tail handling or cupped handling. The mice were then trained in an eight arm radial maze, where two adjacent arms predicted a positive outcome (darkness and food), while the two opposite arms predicted a negative outcome (no food, white noise and light). After six days of training, the mice were also given access to the four previously unavailable intermediate ambiguous arms of the radial maze and tested for cognitive bias. We were unable to validate this test, as mice from both handling groups displayed a similar pattern of exploration. Furthermore, we examined whether maze exploration is affected by the expression of stereotypic behaviour in the home cage. Mice with higher levels of stereotypic behaviour spent more time in positive arms and avoided ambiguous arms, displaying a negative cognitive bias. While this test needs further validation, our results indicate that it may allow the assessment of affective state in mice with minimal training—a major confound in current cognitive bias paradigms.

Tests of unconditioned anxiety - pitfalls and disappointments

The plus-maze, the light-dark box and the open-field are the main current tests of unconditioned anxiety for mice and rats. Despite their disappointing achievements, they remain as popular as ever and seem to play an important role in an ever-growing demand for behavioral phenotyping and drug screening. Numerous reviews have repeatedly reported their lack of consistency and reliability but they failed to address the core question of whether these tests do provide unequivocal measures of fear-induced anxiety, that these measurements are not confused with measures of fear-induced avoidance or natural preference responses - i.e. discriminant validity. In the present report, I examined numerous issues that undermine the validity of the current tests, and I highlighted various flaws in the aspects of these tests and the methodologies pursued. This report concludes that the evidence in support of the validity of the plus-maze, the light/dark box and the open-field as anxiety tests is poor and methodologically questionable.