Exploring transgenerational inheritance in epigenotypes of DAT heterozygous rats: Circadian anomalies and attentional vulnerability

Dopamine (DA) is mainly involved in locomotor activity, reward processes and maternal behaviors. Rats with KO gene for dopamine transporter (DAT), coding for a truncated DAT protein, are in hyperdopaminergic conditions and thus develop stereotyped behaviors and hyperactivity. Our aim was to test the prior transgenerational modulation of wild and truncated alleles as expressed in heterozygous DAT rats: specifically, we addressed the possible sequelae due to genotype and gender of the ancestors, with regard to behavioral differences in F1, F2, F3 rats. We studied non-classical DAT heterozygotes (HETs) based on two specular lines, with putative grand-maternal vs. grand-paternal imprinting. MAT females (F1; offspring of KO male and WT female) mated with a KO male to generate MIX offspring (F2). Specularly, PAT females (F1; offspring of KO female and WT male) mated with a KO male to generate PIX offspring (F2). Similarly to PAT, we obtained MUX (F2; HET offspring of MAT sire and KO dam); we also observed the F3 (MYX: HET offspring of KO male and MUX female, thus with DAT-KO maternal grandmother like also for PIX). We studied their circadian cycle of locomotor activity and their behavior in the elevated-plus-maze (EPM). Locomotor hyper-activity occurs in F1, the opposite occurs in F2, with MYX rats appearing undistinguishable from WT ones. Open-arm preference emerged in PIX and MIX rats. Only MAT and MYX rats showed a significant vulnerability for ADHD-like inattentive symptoms (duration of rearing in the EPM; Viggiano et al., 2002). A risk-taking profile is evident in the F2 phenotype, while inattentiveness from F1 progeny tends to be transferred to F3. We hypothesize that DAT-related phenotypes result from effective inheritance through pedigree of imprints that are dependent on grandparents, suggesting a protective role for gestation within a hyperdopaminergic uterus. For major features, similar odd (F1, F3) generations appear opposed to even (F2) ones; for minor specific features, the phenotype transfer may affect the progenies with a male but not a female DAT-KO ancestor.

The assessment of emotion reactivity: The Italian validation of the Perth Emotional Reactivity Scale-Short Form (PERS-S)

Emotion reactivity refers to the activation, intensity and duration of emotional responses to internal or external stimuli. It can be differentiated from emotion regulation since the former is the very first response to an emotional trigger, and the latter can be defined as a tool for maintaining one's arousal in a window of tolerance. Since, to date, there are no Italian self-report measures able to evaluate individuals' emotional reactivity, this study aimed to contribute to the Italian validation of the Perth Emotional Reactivity Scale-Short Form (PERS-S). The PERS-S is an 18-item self-report measure answered on a 5-point Likert scale that generates six subscale scores and two composite scores, with higher scores indicating higher levels of reactivity. Data from 768 individuals showed that the PERS-S had good to excellent goodness of fit. The internal consistency was high, with an overall reliability coefficient (Cronbach's α) of .87 and .86 for the negative and positive general scales, respectively. The PERS-S also demonstrated appropriate convergent validity, showing significant correlations with conceptually related measures, and acceptable divergent validity, showing minimal correlations with unrelated constructs. Finally, we evaluated the Test-Retest Reliability by administering the PERS-S to the same sample twice, with a 2-week interval. The significant correlations between the two PERS-S administrations suggest temporal stability. The Italian version of the PERS-S will enrich the repertoire of self-report measures for investigating the development and risk factors of mental health disorders and may have practical applications in clinical settings.

Selective alterations of endocannabinoid system genes expression in obsessive compulsive disorder

Obsessive Compulsive Disorder (OCD) is listed as one of the top 10 most disabling neuropsychiatric conditions in the world. The neurobiology of OCD has not been completely understood and efforts are needed in order to develop new treatments. Beside the classical neurotransmitter systems and signalling pathways implicated in OCD, the possible involvement of the endocannabinoid system (ECS) has emerged in pathophysiology of OCD. We report here selective downregulation of the genes coding for enzymes allowing the synthesis of the endocannabinoids. We found reduced DAGLα and NAPE-PLD in blood samples of individuals with OCD (when compared to healthy controls) as well as in the amygdala complex and prefrontal cortex of dopamine transporter (DAT) heterozygous rats, manifesting compulsive behaviours. Also mRNA levels of the genes coding for cannabinoid receptors type 1 and type 2 resulted downregulated, respectively in the rat amygdala and in human blood. Moreover, NAPE-PLD changes in gene expression resulted to be associated with an increase in DNA methylation at gene promoter, and the modulation of this gene in OCD appears to be correlated to the progression of the disease. Finally, the alterations observed in ECS genes expression appears to be correlated with the modulation in oxytocin receptor gene expression, consistently with what recently reported. Overall, we confirm here a role for ECS in OCD at both preclinical and clinical level. Many potential biomarkers are suggested among its components, in particular NAPE-PLD, that might be of help for a prompt and clear diagnosis.

Effects of Physical Activity on Cognitive Functioning: The Role of Cognitive Reserve and Active Aging

BACKGROUND

The increase in average life expectancy necessitates the identification of possible mechanisms capable of promoting "active aging" to ensure adequate levels of global functioning. Numerous studies show that regular physical activity promotes, even in the elderly, a state of functional psychophysical well-being capable of slowing down age-related cognitive decline. This study aimed to clarify whether, and how, the intensity of physical activity can modulate cognitive and executive skills by influencing specific psychological variables.

METHODS

Our sample consisted of 151 senior subjects divided into hikers (HIK), gentle gymnastics (GYM), and sedentary (SED), who practice intense, moderate, and reduced physical activity, respectively. A battery of psychological questionnaires was administrated to evaluate attentional skills, decision-making, the ability to implement targeted behaviors, perceived self-efficacy, and psychophysical well-being. We included: the Mini-Mental State Examination, Cognitive Reserve Index Questionnaire, General Self-Efficacy Scale, Letter Cancellation Test, Everyday Competence Questionnaire, and Geriatric Depression Scale (GDS).

RESULTS

Comparisons between the scores reported by the three groups showed that the HIK group differs from the others with respect to most of the measurements, presenting better mood and cognitive performance, and a specific psychological profile. On the contrary, the GYM group appeared to have a greater affinity with the SED group than with the HIK group, both cognitively and psychologically.

CONCLUSIONS

Types of physical activity, as well as the intensity and frequency with which they are practiced, are factors that promote an active aging process, protecting the psychophysical well-being and overall cognitive functioning of the elderly.

Assessing Resilience to Sleep Loss Among the Italian Population: A 13-Item Model of the Iowa Resistance to Sleeplessness Test (iREST)

Purpose

The present study aimed to validate the Italian version of the Iowa Resistance to Sleeplessness Test (iREST), a 16-item self-report assessing resilience to sleep debt in the affective, cognitive, and somatic domains.

Participants and Methods

We examined its factor structure, assessed internal consistency and criterion validity, and established test-retest reliability on 768 Italian native speakers (65.8% of women) with a mean age of 25.98 years old.

Results

Confirmatory factor analysis (CFA) revealed a new 13-item structure for the Italian iREST (iREST-13), demonstrating more satisfactory goodness-of-fit values, and exhibiting good internal consistency (Cronbach's α ranging from 0.73 to 0.89), relative to the 16-item original version. Results supported the iREST convergent validity, showing significant independence from established measures of sleep; low correlations with conceptually unrelated measures supported divergent validity, indicating that the iREST effectively measures resistance to sleeplessness without confounding with other constructs. Lastly, test-retest reliability was evaluated by administering the iREST to the same sample with a 2-week interval: the significant correlations supported its temporal stability.

Conclusion

Further studies are needed to evaluate the applicability of the iREST in diverse populations and explore its relationship with objective sleep measures. Nevertheless, the Italian iREST provides a valuable tool for assessing resistance to sleep loss, offering insights into individual differences in resilience. Additionally, the iREST can assist in identifying individuals who require interventions to enhance resilience to sleep debt, as well as help clinicians evaluate the impact of chronic sleep disruption and deliver targeted interventions.

Dopamine-transporter heterozygous rats carrying maternal wild-type allele are more vulnerable to the development of compulsive behavior

Compulsivity is defined as an unstoppable tendency towards repetitive and habitual actions, which are reiterated despite negative consequences. Polydipsia is induced preclinically by intermittent reward leading rodents to ingest large amounts of fluids. We focused on the role of dopamine transporter (DAT) and inheritance factors in compulsive behavior. Our sample consisted of DAT heterozygous (HET) rats with different genetic inheritance (MAT-HET, born from WT-dams x KO-fathers; MIX-HET, born from HET-dams x KO-fathers). As controls, we used both wild-type (WT) rats and their socially-isolated (WTi) siblings. We ran the schedule-induced polydipsia (SIP) protocol, to induce compulsive behavior; then the Y-maze and marble-burying tests, to verify its actual development. Only MAT-HET (who inherited the functional DAT allele from the WT mother) is vulnerable to developing compulsive behavior. MAT-HET rats drank increasingly more water during SIP and showed significant perseverance in the Y-maze test and exhibited compulsive actions in the marble-burying test. Interestingly, compulsive behaviors of MAT-HET rats correlate with expression ex-vivo of different genes in different areas. Regarding the prefrontal cortex (PFC), D2R correlates with Y-maze "perseverance" in addition to BDNF; considering the amygdala (AMY), both D3R and OXTR correlate with SIP "licks". Indeed, compulsivity may be linked to D2R and BDNF in PFC, while extreme anxiety in MAT-HET rats may be associated with D3R and OXTR in the amygdala. These results confirm some similarities between MAT-HET and DAT-KO subjects and link the epigenetic context of the DAT gene to the development of compulsive behavior. This article is protected by copyright. All rights reserved.

Altering the development of the dopaminergic system through social play in rats: Implications for anxiety, depression, hyperactivity, and compulsivity

Dopamine is essential to many functions like reward, motivation, and attention; when its neural pathways do not function properly, various disorders (e.g., anxiety, depression, hyperactivity, compulsions) can arise. Truncated-DAT rats display persistent stereotypies and aggressiveness; hence they are a new valuable animal model to study the pathogenesis of these disorders. The focus of research is often on the individual epigenetic determinants and much less on the impact of social experiences. Here, we investigate the developmental impact of the social environment on adolescent wild type (WT) rats. We divided subjects at weaning into three groups: living with another adolescent (WT Peer), with a WT adult, or with a truncated-DAT one, and we observed homecage social behavior of these pairs (play, jump, victory, and "bullying") during whole adolescence. When adult, we observed the same subjects in plus maze, forced swim, and social preference tests to measure levels of anxiety, depression, and quality of social interactions. Compared to the other groups, WT rats that had spent their adolescence with a truncated-DAT adult as companion show more anxious, depressive, hyperactive, impulsive, and compulsive behaviours. Results confirm that social interactions and healthy play (i.e., when play has behavioural, social, and psychomotor rewards that support the cognitive, emotional and physical development of the individual) are essential to neurobehavioral maturation. Conversely, anomalous interactions like poor play and "bullying" in developing rats may impact onto their dopaminergic system. Consequently, an impoverished social play could be one of the factors contributing to the appearance of putative indexes of attention deficit hyperactivity disorder (ADHD) and\or obsessive-compulsive disorder (OCD).

"Himalayan Bridge": A New Unstable Suspended Bridge to Investigate Rodents' Venturesome Behavior

While both risk-taking and avoidant behaviors are necessary for survival, their imbalanced expression can lead to impulse-control and anxiety disorders, respectively. In laboratory rodents, the conflict between risk proneness and anxiety can be studied by using their innate fear of heights. To explore this aspect in detail and investigate venturesome behavior, here we used a "Himalayan Bridge," a rat-adapted version of the suspended wire bridge protocol originally developed for mice. The apparatus is composed of two elevated scaffolds connected by bridges of different lengths and stability at 1 m above a foam rubber-covered floor. Rats were allowed to cross the bridge to reach food, and crossings, pawslips, turnabouts, and latencies to cross were measured. Given the link between risky behavior and adolescence, we used this apparatus to investigate the different responses elicited by a homecage mate on the adolescent development of risk-taking behavior. Thus, 24 wild-type (WT) subjects were divided into three different housing groups: WT rats grown up with WT adult rats; control WT adolescent rats (grown up with WT adolescents), which showed a proclivity to risk; and WT rats grown up with an adult rat harboring a truncated mutation for their dopamine transporter (DAT). This latter group exhibited risk-averse responses reminiscent of lower venturesomeness. Our results suggest that the Himalayan Bridge may be useful to investigate risk perception and seeking; thus, it should be included in the behavioral phenotyping of rat models of psychiatric disorders and cognitive dysfunctions.

A new paradigm for Prosocial Behavior and Reciprocity, assessed in WT and HET rats for the DAT gene

Most behavioral studies on animals focus on observation of individual subjects. Current paradigms of sociability set aside the social-operant dimension, i.e. acting in favor of another conspecific. We focused on prosocial behavior and reciprocity of male, adult Wild-Type (WT) and Heterozygous (HET) rats for the dopamine-transporter (DAT) gene. METHOD: The experiment consisted of 24 rats, of WT (n = 12) and HET (n = 12) genotypes. During training, rats were daily introduced, individually, into an apparatus hosting a suspended syringe, which they learnt to push in order to obtain food therein. Then, twice daily along several weeks, we introduced two rats separated by a grid in the same structure: by syringe-pushing, each subject had the opportunity to donate and receive donations of food. We tested pairs with similar versus different genotype. Eventually, we replaced food reward with polystyrene pieces, to understand if they pushed for actual reward or like a habit. RESULTS: In general, WT rats had better performance, regardless of reward type, than HET ones. When we crossed partner rats' genotype (WT-HET pairs), WT rats pushed at peak levels, regardless of food pellet received back (in fact, HET companions pushed less). Couples of WT rats achieved better results than HET ones even when polystyrene, instead of food, was used. Thus,WT rats seem to be a better model for altruistic behavior than HET ones. For this reason, HET rats could represent a model for studies on altered prosocial behavior, to understand the role of DAT gene for impaired social mechanisms.

Intersections and Divergences Between Empathizing and Mentalizing: Development, Recent Advancements by Neuroimaging and the Future of Animal Modeling

Both mentalization and empathy allow humans to understand others, through the representation of their mental states or their mood, respectively. The present review aims to explain those characteristics which are shared between empathy and the Theory of Mind. Research in neuroscience, based on naturalistic paradigms, has shown that abilities to mentalize and to empathize are associated with the activation of different neuro-cognitive circuits. As far as mirror-neuron processes are concerned, some structures (like Anterior Insula, AI; Anterior Cingulate Cortex, ACC) play a role both in the representation of one's own affective states and in comprehension of the same affective state when experienced by others. As for mentalization, the temporal parietal junction (TPj) and temporal poles (TP), the upper posterior temporal sulcus (pSTS) and the medial prefrontal cortex (mPFC) are greatly involved: the latter appears involved in the attribution of one's own and others' temperaments. Interestingly, the ventral/orbital portion of the PFC (orbito-frontal cortex, OFC) is involved in subserving shared affective experience during cognitive mentalizing. This brain region represents a point of overlap, from a psycho-biological point of view, where emotional mirroring and affective cognition meet up. As for animal models, laboratory rodents can well be tested for prosocial behavior. Some examples include deliberate actions, allowing another conspecific the possibility to feed ("giving food"): this willingness can vary across donors, depending on how the recipient is perceived. Other examples include the possibility to let a trapped conspecific come out ("giving help"). The state-of-the-art knowledge about this theme can inform the programming of specific clinical interventions, based on the reinforcement of empathic and/or mentalization abilities.