A behavioural test battery to investigate tic-like symptoms, stereotypies, attentional capabilities, and spontaneous locomotion in different mouse strains

Automation at the service of the study of executive functions in preclinical models

Cognitive flexibility involves the capability to switch between different perspectives and implement novel strategies upon changed circumstances. The Wisconsin Card Sorting Test (in humans) and the Attentional Set-Shifting Task (ASST, in rodents) evaluate individual capability to acquire a reward-associated rule and subsequently disregard it in favour of a new one. Both tasks entail consecutive stages wherein subjects discriminate between: two stimuli of a given category (simple discrimination, SD); the stimuli of SD confounded by an irrelevant stimulus of a different category (compound discrimination, CD); different stimuli belonging to the SD category (intradimensional shift, IDS); and two stimuli of the confounding category (extradimensional shift, EDS). The ASST is labour intensive, not sufficiently standardised, and prone to experimental error. Here, we tested the validity of a new, commercially available, automated version of ASST (OPERON) in two independent experiments conducted in: different mouse strains (C57BL/6 and CD1 mice) to confirm their differential cognitive capabilities (Experiment 1); and an experimental model of chronic stress (administration of corticosterone in the drinking water; Experiment 2). In both experiments, OPERON confirmed the findings obtained through the manual version. Just as in Experiment 1 both versions captured the deficit of C57BL/6 mice on the reversal of the CD (CDR), so also in Experiment 2 they provided analogous evidence that corticosterone treated mice have a remarkable impairment in the IDS. Thus, OPERON capitalises upon automated phenotyping to overcome the limitation of the manual version of the ASST while providing comparable results.

Effects of Chemogenetic Inhibition of D1 or D2 Receptor-Containing Neurons of the Substantia Nigra and Striatum in Mice With Tourette Syndrome

As tourette syndrome (TS) is a common neurobehavioral disorder, the primary symptoms of which include behavioral stereotypies. Dysfunction of the substantia nigra-striatum network could be the main pathogenesis of TS, which is closely associated with dopamine (DA) and its receptors. TS is often resistant to conventional treatments. Therefore, it is necessary to investigate the neurobiological mechanisms underlying its pathogenesis. In this study, we investigated whether chemogenetic activation or inhibition of dopaminergic D1 receptor (D1R)- or D2 receptor (D2R)-containing neurons in the substantia nigra pars compacta (SNpc) or dorsal striatum (dSTR) affected the stereotyped behavior and motor functions of TS mice. Intraperitoneal injection of 3,3'-iminodipropionitrile (IDPN) was used to induce TS in mice. Stereotyped behavior test and open-field, rotarod, and grip strength tests were performed to evaluate stereotyped behavior and motor functions, respectively. Immunofluorescence labeling was used to detect the co-labeling of virus fluorescence and D1R or D2R. We found that chemogenetic inhibition of D1R- or D2R-containing neurons in the SNpc and dSTR alleviated behavioral stereotypies and motor functions in TS mice. Chemogenetic activation of D1R-containing neurons in the dSTR aggravated behavioral stereotypies and motor functions in vehicle-treated mice, but neither was aggravated in TS mice. In conclusion, chemogenetic inhibition of D1R- or D2R-containing neurons in the SNpc and dSTR alleviated behavioral stereotypies of TS, providing a new treatment target for TS. Moreover, the activation of D1R-containing neurons in the dSTR may contribute to the pathogenesis of TS, which can be chosen as a more precise target for treatment.

Sialylated human milk oligosaccharides program cognitive development through a non-genomic transmission mode

Breastmilk contains bioactive molecules essential for brain and cognitive development. While sialylated human milk oligosaccharides (HMOs) have been implicated in phenotypic programming, their selective role and underlying mechanisms remained elusive. Here, we investigated the long-term consequences of a selective lactational deprivation of a specific sialylated HMO in mice. We capitalized on a knock-out (KO) mouse model (B6.129-St6gal1^tm2Jxm/J) lacking the gene responsible for the synthesis of sialyl(alpha2,6)lactose (6'SL), one of the two sources of sialic acid (Neu5Ac) to the lactating offspring. Neu5Ac is involved in the formation of brain structures sustaining cognition. To deprive lactating offspring of 6'SL, we cross-fostered newborn wild-type (WT) pups to KO dams, which provide 6'SL-deficient milk. To test whether lactational 6'SL deprivation affects cognitive capabilities in adulthood, we assessed attention, perseveration, and memory. To detail the associated endophenotypes, we investigated hippocampal electrophysiology, plasma metabolomics, and gut microbiota composition. To investigate the underlying molecular mechanisms, we assessed gene expression (at eye-opening and in adulthood) in two brain regions mediating executive functions and memory (hippocampus and prefrontal cortex, PFC). Compared to control mice, WT offspring deprived of 6'SL during lactation exhibited consistent alterations in all cognitive functions addressed, hippocampal electrophysiology, and in pathways regulating the serotonergic system (identified through gut microbiota and plasma metabolomics). These were associated with a site- (PFC) and time-specific (eye-opening) reduced expression of genes involved in central nervous system development. Our data suggest that 6'SL in maternal milk adjusts cognitive development through a short-term upregulation of genes modulating neuronal patterning in the PFC.

Effects of Acupuncture on Behavioral Stereotypies and Brain Dopamine System in Mice as a Model of Tourette Syndrome

Tourette syndrome (TS), a developmental neurobehavioral disorder, is characterized by involuntary behavioral stereotypies. Clinical studies have confirmed the positive effect of acupuncture on treating TS, but the underlying mechanisms are not fully understood. In the present study, we used behavioral tests, Western blotting, double-immunofluorescence labeling, and fluorescence spectrophotometry to investigate whether acupuncture performed at acupoints "Baihui" (GV20) and "Yintang" (GV29) affected behavioral stereotypies and regulated the dopamine (DA) system in three different brain regions in Balb/c mice injected with 3,3'-iminodipropionitrile (IDPN) as a model for TS. We found that acupuncture alleviated behavioral stereotypies, down-regulated the expression of D1R and D2R in the striatum (STR) and substantia nigra pars compacta (SNpc), and decreased the concentration of DA in the STR, SNpc, and prefrontal cortex (PFC) as well. Moreover, acupuncture reduced the expression of tyrosine hydroxylase (TH) in the SNpc. Conclusively, acupuncture ameliorated behavioral stereotypies by regulating the DA system in the STR, SNpc, and PFC. Our findings provide novel evidence for the therapeutic effect of acupuncture on TS.

Methylphenidate administration promotes sociability and reduces aggression in a mouse model of callousness

RATIONALE

Deficits in empathy constitute a distinctive feature of several psychopathologies, including conduct disorder (CD). The co-occurrence of callous-unemotional (CU) traits, excess rates of aggression and violation of societal norms confers specific risk for adult psychopathy. To date, the off-label use of methylphenidate (MPH) constitutes the drug treatment of choice.

OBJECTIVES

Herein, we tested the therapeutic potential of MPH in a recently devised mouse model recapitulating the core phenotypic abnormalities of CD.

METHODS

Two subgroups of BALB/cJ male mice exhibiting opposite profiles of emotional contagion (i.e. socially transmitted adoption of another's emotional states) were investigated for reactive aggression, sociability, attention control, anxiety-related behaviours and locomotor activity, in response to MPH administration (0.0, 3.0 or 6.0 mg/kg).

RESULTS

Our data indicate that mice selected for excess callousness exhibit phenotypic abnormalities isomorphic to the symptoms of CD: stability of the low emotional contagion trait, increased aggression and reduced sociability. In accordance with our predictions, MPH reduced aggression and increased sociability in callous mice; yet, it failed to restore the low responsiveness to the emotions of a conspecific in pain, isomorphic to CU traits.

CONCLUSIONS

Although our data support the notion that MPH may contribute to the management of excess aggression in CD patients, additional studies shall identify specific treatments to target the callousness domain. The latter, unaffected by MPH in our experimental model, demands focused consideration whereby it constitutes a specifier associated with a worse prognosis.

Psychostimulant Effect of the Synthetic Cannabinoid JWH-018 and AKB48: Behavioral, Neurochemical, and Dopamine Transporter Scan Imaging Studies in Mice

JWH-018 and AKB48 are two synthetic cannabinoids (SCBs) belonging to different structural classes and illegally marketed as incense, herbal preparations, or chemical supply for theirs psychoactive cannabis-like effects. Clinical reports from emergency room reported psychomotor agitation as one of the most frequent effects in people assuming SCBs. This study aimed to investigate the psychostimulant properties of JWH-018 and AKB48 in male CD-1 mice and to compare their behavioral and biochemical effects with those caused by cocaine and amphetamine. In vivo studies showed that JWH-018 and AKB48, as cocaine and amphetamine, facilitated spontaneous locomotion in mice. These effects were prevented by CB₁ receptor blockade and dopamine (DA) D_1/5 and D_2/3 receptors inhibition. SPECT-CT studies on dopamine transporter (DAT) revealed that, as cocaine and amphetamine, JWH-018 and AKB48 decreased the [¹²³I]-FP-CIT binding in the mouse striatum. Conversely, in vitro competition binding studies revealed that, unlike cocaine and amphetamine, JWH-018 and AKB48 did not bind to mouse or human DAT. Moreover, microdialysis studies showed that the systemic administration of JWH-018, AKB48, cocaine, and amphetamine stimulated DA release in the nucleus accumbens (NAc) shell of freely moving mice. Finally, unlike amphetamine and cocaine, JWH-018 and AKB48 did not induce any changes on spontaneous [³H]-DA efflux from murine striatal synaptosomes. The present results suggest that SCBs facilitate striatal DA release possibly with different mechanisms than cocaine and amphetamine. Furthermore, they demonstrate, for the first time, that JWH-018 and AKB48 induce a psychostimulant effect in mice possibly by increasing NAc DA release. These data, according to clinical reports, outline the potential psychostimulant action of SCBs highlighting their possible danger to human health.

Mice repeatedly exposed to Group-A β-Haemolytic Streptococcus show perseverative behaviors, impaired sensorimotor gating, and immune activation in rostral diencephalon

Repeated exposure to Group-A β-Haemolytic Streptococcus (GAS) may constitute a vulnerability factor in the onset and course of pediatric motor disturbances. GAS infections/colonization can stimulate the production of antibodies, which may cross the blood brain barrier, target selected brain areas (e.g. basal ganglia), and exacerbate motor alterations. Here, we exposed developing SJL male mice to four injections with a GAS homogenate and evaluated the following domains: motor coordination; general locomotion; repetitive behaviors; perseverative responses; and sensorimotor gating (pre-pulse inhibition, PPI). To demonstrate that behavioral changes were associated with immune-mediated brain alterations, we analyzed, in selected brain areas, the presence of infiltrates and microglial activation (immunohistochemistry), monoamines (HPLC), and brain metabolites (in vivo Magnetic Resonance Spectroscopy). GAS-exposed mice showed increased repetitive and perseverative behaviors, impaired PPI, and reduced concentrations of serotonin in prefrontal cortex, a brain area linked to the behavioral domains investigated, wherein they also showed remarkable elevations in lactate. Active inflammatory processes were substantiated by the observation of infiltrates and microglial activation in the white matter of the anterior diencephalon. These data support the hypothesis that repeated GAS exposure may elicit inflammatory responses in brain areas involved in motor control and perseverative behavior, and result in phenotypic abnormalities.

The Snark was a Boojum - reloaded

In this article, we refer to an original opinion paper written by Prof. Frank Beach in 1950 ("The Snark was a Boojum"). In his manuscript, Beach explicitly criticised the field of comparative psychology because of the disparity between the original understanding of comparativeness and its practical overly specialised implementation. Specialisation encompassed both experimental species (rats accounted for 70% of all subjects) and test paradigms (dominated by conditioning/learning experiments). Herein, we attempt to evaluate the extent to which these considerations apply to current behavioural neuroscience. Such evaluation is particularly interesting in the context of "translational research" that has recently gained growing attention. As a community, we believe that preclinical findings are intended to inform clinical practice at the level of therapies and knowledge advancements. Yet, limited reproducibility of experimental results and failures to translate preclinical research into clinical trial sindicate that these expectations are not entirely fulfilled. Theoretical considerations suggest that, before concluding that a given phenomenon is of relevance to our species, it should be observed in more than a single experimental model (be it an animal strain or species) and tested in more than a single standardized test battery. Yet, current approaches appear limited in terms of variability and overspecialised in terms of operative procedures. Specifically, as in 1950, rodents (mice instead of rats) still constitute the vast majority of animal species investigated. Additionally, the scientific community strives to homogenise experimental test strategies, thereby not only limiting the generalizability of the findings, but also working against the design of innovative approaches. Finally, we discuss the importance of evolutionary-adaptive considerations within the field of laboratory research. Specifically, resting upon empirical evidence indicating that developing individuals adjust their long-term phenotype according to early environmental demands, we propose that current rearing and housing standards do not adequately prepare experimental subjects to their actual adult environments. Specifically, while the adult life of a laboratory animal is characterized by frequent stimulations and challenges, the neonatal life is dominated by quietness and stability. We suggest that such form of mismatch may remarkably influence the reproducibility and reliability of experimental findings.

Tourette Syndrome research highlights 2014

About 200 journal articles reported research on Tourette syndrome and other tic disorders in 2014. Here we briefly summarize a few of the reports that seemed most important or interesting, ranging from animal models to human studies. Readers can comment on our choices or provide their own favorites using the tools on the online article.

Interaction between the endocannabinoid and serotonergic system in the exhibition of head twitch response in four mouse strains

More than 10 % of children during school years suffer from a transient tic disorder, and 1 % has a particular type of tic disorder known as Tourette syndrome. At present, there is no available treatment that can improve tics without considerable side effects. Recent evidence indicates that tetrahydrocannabinol (THC), the principal psychoactive component of cannabis, reduced in mice the head twitch responses, a tic pharmacologically induced by the selective serotonin 5-HT2 receptor agonist 2,5-dimethoxy-4-iodoamphetamine (DOI). THC has some considerable side effects that render its use problematic. In this view, cyclohexyl-carbamic acid 3'-carbamoyl-biphenyl-3-yl ester (URB597), an indirect cannabinoid agonist that enhances endogenous anandamide levels, can constitute a valid alternative to the use of direct CB1 receptor agonists. We investigated whether URB597 may reduce the exhibition of DOI-induced head twitch responses in mice. Moreover, to address whether the effects of URB597 on DOI-induced behavioral response constitute a general phenomenon, we evaluated four (ABH, C57BL/6N, SJL/J, CD-1) mouse strains. These strains have been selected in order to represent an ample spectrum of genetic background and phenotypic variation. Predictably, DOI induced consistent tic-like behaviors in all mice. While URB597 exerted slight sedation in C57BN/6L mice, this cannabinoid agonist remarkably mitigated the exhibition of DOI-induced head twitch in all strains. Present data may disclose novel avenues for the pharmacological treatment of tic disorders.

Animal models of tic disorders: a translational perspective

Tics are repetitive, sudden movements and/or vocalizations, typically enacted as maladaptive responses to intrusive premonitory urges. The most severe tic disorder, Tourette syndrome (TS), is a childhood-onset condition featuring multiple motor and at least one phonic tic for a duration longer than 1 year. The pharmacological treatment of TS is mainly based on antipsychotic agents; while these drugs are often effective in reducing tic severity and frequency, their therapeutic compliance is limited by serious motor and cognitive side effects. The identification of novel therapeutic targets and development of better treatments for tic disorders is conditional on the development of animal models with high translational validity. In addition, these experimental tools can prove extremely useful to test hypotheses on the etiology and neurobiological bases of TS and related conditions. In recent years, the translational value of these animal models has been enhanced, thanks to a significant re-organization of our conceptual framework of neuropsychiatric disorders, with a greater focus on endophenotypes and quantitative indices, rather than qualitative descriptors. Given the complex and multifactorial nature of TS and other tic disorders, the selection of animal models that can appropriately capture specific symptomatic aspects of these conditions can pose significant theoretical and methodological challenges. In this article, we will review the state of the art on the available animal models of tic disorders, based on genetic mutations, environmental interventions as well as pharmacological manipulations. Furthermore, we will outline emerging lines of translational research showing how some of these experimental preparations have led to significant progress in the identification of novel therapeutic targets for tic disorders.