Rat self-grooming and its relationships with anxiety, dearousal and perseveration: Evidence for a self-grooming trait

Tetrapleura tetraptera fruit extracts ameliorate pentylenetetrazol-induced seizures as well as ensuing cognitive deficit and oxidative stress

Kindling is an experimental-induced seizure consistent with epilepsy disease, a chronic neurological disorder characterised by spontaneous and repeated seizures. This disease is associated with oxidative stress, and most therapeutic strategies against epilepsy aim at improving the antioxidant defence mechanism in the brain. However, prolonged usage and associated adverse side effects limit antiepileptics, warranting natural antioxidant patronage. The present study investigated the behavioural and antioxidant actions of Tetrapleura tetraptera fruit extracts (TT) against pentylenetetrazol (PTZ)-kindling rats. Twenty-five male Wistar rats (150-180 g) were assigned into five groups (1-5, n = 5): Control (normal saline, 5 ml/kg body weight, b.w.), PTZ-only (40 mg/kg/b.w. i.p.), and groups 3-5 administered PTZ (40 mg/kg/b.w. i.p.) after, respectively, receiving oral TT (500 mg/kg/b.w.), TT flavonoid (fTT, 50 mg/kg/b.w.), and sodium valproate (SV, 15 mg/kg/b.w.). All administrations were carried out 48 hourly for 21 days. In the end, buried food, novel object recognition (NOR), Y-maze, elevated plus maze (EPM), and beam walk tests were done, and the rats were sacrificed. Whole brains were processed for antioxidant assays. The results showed a high (p <.05) seizure score and buried food test latency, preference for the familiar object in the NOR test, aversion to open-arm and reduced grooming in the EPM, reduced beam walk latency, elevated brain malondialdehyde (MDA), and decreased superoxide dismutase (SOD) in the PTZ group. The TT, fTT, and SV suppressed seizure, decreased buried food latency, `preference for the novel object and open-arm, increased grooming, decreased brain MDA, and elevated SOD. In conclusion, TT extracts protected against PTZ-induced cognitive deficits and brain oxidative stress, with results similar to those of the standard anticonvulsant drug, SV.

Postpartum dams exposed to a low-resource environment display neuroinflammation, elevated corticosterone, and anhedonia-like behavior

Women living in an impoverished environment after birth have an increased risk of developing postpartum depression (PP-Dep) and hypertension (PP-HTN). The mechanisms underlying these heightened risks are unknown and understudied. To examine the relation between reduced environmental resources, PP-Dep, and PP-HTN, postpartum rodent dams were exposed to the low-resource limited bedding and nesting (LBN) chronic stress model during weaning. Postpartum dams were divided into control (CTL) and experimental (LBN) groups, in which the experimental group experienced LBN. At 6 wks postpartum, blood pressure, sucrose preference tests (a proxy for anhedonia and depression), corticosterone, and markers of neuroinflammation were measured. We hypothesized that postpartum dams exposed to LBN will have increased corticosterone, neuroinflammation, depression-like behaviors, and HTN. Results show that postpartum dams exposed to an impoverished environment exhibit decreased sucrose preference, increased circulating corticosterone, and elevated neuroinflammation (∼150% increased TNF-α and astrocyte activation in the cerebrum). No changes in blood pressure were observed. However, there was a strong correlation between postpartum blood pressure and corticosterone and blood pressure and TNF-α levels. Importantly, this study provides insights into the pathology and development of PP-HTN and PP-Dep in the postpartum period, which will enable the discovery of novel therapeutic approaches.NEW & NOTEWORTHY Postpartum dams exposed to a low-resource environment experience anhedonia, elevated corticosterone, and neuroinflammation. Increases in corticosterone and neuroinflammation may contribute to the development of postpartum depression (PP-Dep) and postpartum hypertension (PP-HTN). Healthcare providers should consider asking questions about the social economic status and accessibility of resources for women after pregnancy. This study advocates for extended postpartum care beyond traditional care and better implementation of assessments for PP-Dep and PP-HTN.

Distinct Effects of Olanzapine Depot Treatment on Behavior and Muscarinic M1 Receptor Expression in the Triple-Hit Wisket Rat Model of Schizophrenia

This study aimed to characterize the triple-hit schizophrenia-like model rats (Wisket) by the assessment of (1) behavioral parameters in different test conditions (reward-based Ambitus test and HomeManner system) for a prolonged period, (2) cerebral muscarinic M1 receptor (M1R) expression, and (3) the effects of olanzapine treatment on these parameters. Wistar (control) and Wisket rats were injected for three consecutive weeks with olanzapine depot (100 mg/kg) and spent 4 weeks in large cages with environmental enrichment (HomeManner). The vehicle-treated Wisket rats spent longer time awake with decreased grooming activity compared to controls, without changes in their active social behavior (sniffing, playing, fighting) obtained in HomeManner. Olanzapine treatment decreased most of these parameters, only the passive social interaction (huddling during sleeping) enhanced mostly in the Wisket rats on the injection day, which recovered within 4 days. In the Ambitus test, vehicle-treated Wisket rats showed lower locomotor and exploratory activities and impaired cognition compared to control rats, deteriorating by olanzapine in both groups. In Wisket brain samples, the M1R mRNA expression was significantly lower in the cerebral cortex and elevated in the hippocampus, with no difference in the prefrontal cortex versus control. Olanzapine normalized the hippocampal M1R expression, but enhanced it in the prefrontal cortex. The triple-hit Wisket model rats had impaired behavioral characteristics in both acute reward-based test and undisturbed circumstances investigated for prolonged periods, and altered cerebral M1R expression. Chronic olanzapine treatment resulted deterioration of some parameters in control group, and could restore only few negative signs in model rats.

A meta-analysis approach to evaluate the effects of early group housing on calf performance, health, and behavior during the preweaning period

This study aimed to evaluate the effects of early group housing on the performance, health, and behavior of dairy calves during the preweaning period using systematic and meta-analysis approaches. Peer-reviewed articles written in English that compared dairy calves individually and group-housed with performance, health, or behavior outcomes were collected from Web of Science, PubMed, and CABDirect databases. The resulting articles (n = 850) underwent a 4-step appraisal process following the Preferred Reporting Items for Systematic Review and Meta-Analyses protocols, resulting in a final sample of 51 articles containing 85 studies. The weighted or standardized mean differences between individually housed and group-housed (pair or group with >2 calves) calves were analyzed for each variable using the DerSimonian and Laird methods. Heterogeneity between calf housing systems was evaluated by the χ2 test and I2 statistics. A meta-regression analysis was conducted to identify categorical covariate effects for variables with high heterogeneity. Most of the studies included in this review evaluated female calves (45.8%) weaned at 8 wk old (52.6%). Housing systems were mainly paired housing (55.3%), followed by groups of 3 to 6 calves (30.65) and groups of 7 to 15 calves (4.7%). We did not find studies with comparable outcomes for more robust health parameters (as occurrence of diseases), only blood parameters, that were not influenced by the housing system. However, weight gain and feed intake parameters were higher in group-housed calves. Through the meta-regression, we found that ADG was positively affected by the group housing in studies with calves housed in small pen areas (<1.5 m2 per calf). Group-housed calves presented more active behaviors (feeding and playing) and less stress-related behaviors (self-grooming and interacting with the pen) than individually housed calves. The behavioral tests most used were novel object, human approach, novel environment, and social tests. Individually housed calves presented fewer vocalizations on these tests and spent more time interacting with humans during the human approach test than group-housed calves. Our findings provide consistent evidence that group housing improves the welfare of dairy calves; however, the effects on health parameters are still scarce and unclear.

Rauvolfia vomitoria phenol extract relieves pentylenetetrazol-induced seizures in Swiss mice and protects some temporal lobe structures

BACKGROUND

Rauvolfia vomitoria (R. vomitoria) is a plant of economic importance due to its diverse ethnomedicinal properties, including the anticonvulsant effect. In this study, we studied the antiseizure and neuroprotective potentials of R. vomitoria extracts against pentylenetetrazol (PTZ)-induced kindling.

METHODS

Twenty-five adult Swiss mice (25-30 g) were assigned to five groups (n = 5): control group, PTZ treatment group, and PTZ treatment after receiving oral R. vomitoria crude extract (100 mg/kg), R. vomitoria phenol extract (50 mg/kg) or sodium valproate (15 mg/kg) every 48 h for 28 days. Seizure scores, cognitive behavioral tests including novel object test, Y-maze test, and the elevated plus maze test, as well as brain neurochemicals and histomorphology studies, were performed.

RESULTS

Compared with the control group, the PTZ group showed comparable body weight and durations in closed and open arms (P > 0.05), but preference for familiar objects, significant (P < 0.05) spontaneous alternation, increased monoamine oxidase activity and nitric oxide level, and Nissl chromatolysis in the temporal lobe structures including the cortex, hippocampus, and amygdala. R. vomitoria phenol extract pretreatment significantly (P < 0.05) reduced seizures, prevented adverse cognitive behaviors, decreased the nitric oxide level, and reduced the temporal lobe Nissl chromatolysis compared with the R. vomitoria crude extract pretreatment group and the sodium valproate pretreatment groups.

CONCLUSIONS

Thus, R. vomitoria phenol extract showed promising results against seizures and potential for general brain protection, suggesting that the anticonvulsant property of R. vomitoria may be attributed to its phenol constituent. More studies are needed to delineate the mechanisms of its action.

Differences in memory performance: The effects of sex and reproductive experience on object recognition memory in high- and low-yawning Sprague‒Dawley rats

The novel object recognition (NOR) test is an efficient way to measure nonspatial memory in rodents. The NOR performance of female and male rats is sexually dimorphic because memory performance is better in the former than in the latter. In females, maternal experience enhances spatial memory. We used the NOR test to evaluate short- and long-term recognition memory in both sexes in the high- and low-yawning sublines of rats (HY and LY, respectively), which were generated via a strict inbreeding process from the Sprague‒Dawley (SD) strain for more than ninety generations. Additionally, we evaluated the effect of maternal experience using nulliparous, primiparous, biparous, and multiparous HY, LY and SD dams. Our results revealed that LY rats presented less thigmotaxis, with lower central square crosses and more vertical exploration in the open-field arena, suggesting that they experienced anxiety. Additionally, LY males performed significantly better than LY females in short- and long-term NOR memory, and LY males performed significantly better than SD rats did. Among females, two maternal experiences negatively affected short-term memory in the LY and HY sublines with respect to primiparous dams, and HY dams had better memory performance in the NOR test than did SD dams. Our findings suggest that the yawning sublines are suitable for studying the neurobiological basis of different memory processes under different endocrine conditions in highly inbred groups of rats.

Stress enhances aggression in male rats with genetic stress hyper-reactivity

The current study investigated stress-induced aggressive behavior in the resident-intruder test in males of the genetically stress hyper-reactive Wistar Kyoto More Immobile (WMI), and the nearly isogenic, control Wistar Kyoto Less Immobile (WLI) strains. Tests were carried out against same-age intruders during adolescence, and same-age and juvenile intruders in adulthood. In adolescence and adulthood, prior acute restraint stress decreased social interactions and decreased aggressive behaviors of adolescents and adult WLIs. However, prior stress precipitated aggression in the adult WMI males toward both same-age, and juvenile intruders compared with control WMIs and WLIs. Trunk blood levels of testosterone and androstenedione increased in stressed WLIs, but not in WMIs, suggesting no direct role of androgens in the increased aggression of WMIs. Expressions of aggression-relevant genes showed patterns commensurate with being causative in aggressive behavior. The methyl-CpG binding protein 2 was lower in the frontal cortex of control WMIs, and in the amygdala of stressed WMIs compared with their respective WLIs. Frontal cortex expression of vasopressin receptor 1a and serotonin transporter increased, solely in WMI males after stress. As behaviors were the same toward same-age and non-threatening juvenile intruders, the stress-induced increase in confrontational behavior of the adult WMI male was not because of enhanced fear or anxiety. These results suggest that genetic stress hyper-reactivity is a risk factor for stress-induced increases in aggression in males. Additionally, as known aggression-related genes showed expression patterns paralleling aggressive behavior, this model system could identify novel molecular pathways leading to stress-enhanced aggression.

Selective estrogen receptor activation prior to global cerebral ischemia in female rats impacts microglial activation and anxiety-like behaviors without effects on CA1 neuronal injury

Estrogen receptor (ER) activation by 17-ß estradiol (E2) can attenuate neuronal injury and behavioral impairments following global cerebral ischemia (GCI) in rodents. This study sought to further examine the discrete roles of ERs through characterization of the effects of selective ER activation on post-ischemic pro-inflammatory microglial activation, hippocampal neuronal injury, and anxiety-like behaviors. Forty-six ovariectomized (OVX) adult female Wistar rats received daily s.c injections (100 μg/kg/day) of propylpyrazole triol (PPT; ERα agonist), diarylpropionitrile (DPN; ERβ agonist), G-1 (G-protein coupled ER agonist; GPER), E2 (activating all receptors), or vehicle solution (VEH) for 21 days. After final injection, rats underwent GCI via 4-vessel occlusion (n=8 per group) or sham surgery (n=6, vehicle injections). The Open Field Test (OFT), Elevated Plus Maze (EPM), and Hole Board Test (HBT) assessed anxiety-like behaviors. Microglial activation (Iba1, CD68, CD86) in the basolateral amygdala (BLA), CA1 of the hippocampus, and paraventricular nucleus of the hypothalamus (PVN) was determined 8 days post-ischemia. Compared to sham rats, Iba1 activation and CA1 neuronal injury were increased in all ischemic groups except DPN-treated rats, with PPT-treated ischemic rats also showing increased PVN Iba1-ir expression. Behaviorally, VEH ischemic rats showed slightly elevated anxiety in the EPM compared to sham counterparts, with no significant effects of agonists. While no changes were observed in the OFT, emotion regulation via grooming in the HBT was increased in G-1 rats compared to E2 rats. Our findings support selective ER activation to regulate post-ischemic microglial activation and coping strategies in the HBT, despite minimal impact on hippocampal injury.

Schizophrenia-relevant social, attentional and cognitive traits in female RHA vs. RLA rats: Effects of neonatal handling

The Roman high- (RHA) and low-avoidance (RLA) rats were bidirectionally selected and bred for, respectively, their rapid vs. extremely poor acquisition in the two-way active avoidance task. Consistent between-strain neurobehavioural differences have been found in anxiety- and stress-linked traits, as well as in schizophrenia-related phenotypes. RLAs display enhanced anxious- and stress-related phenotypes, whereas RHA rats show impulsivity, hyperactivity and attention/cognition-related impairments. Many of these typical behavioural phenotypes have been reported to be positively modulated by environmental treatments such as neonatal handling (NH). However, most studies on the Roman rat strains have been carried out in males. Thus, the present study for the first time focused on the joint evaluation of differences in novel object exploration (NOE), social interaction (SI), prepulse inhibition of the startle response (PPI), and cognitive performance and flexibility in various spatial tasks (using the Morris water maze, MWM) in females of both Roman rat strains. We also aimed at evaluating the long-lasting effects of NH treatment on the RHA vs. RLA profiles in these tests/tasks. Results show that anxiety-related behavior, as measured by the NOE test and self-grooming in the SI test, was increased in RLA rats, and dramatically reduced by NH. In the SI test RLA rats displayed diminished social interaction, which was rescued by NH. RHA females exhibited a deficit of PPI, which was not affected by NH. Spatial tasks in the MWM showed impairments of working memory, reference learning/memory and spatial reversal learning (i.e., cognitive flexibility) in RHA females. Spatial reference learning and cognitive flexibility (i.e., reversal task) showed some improvement in rats (mainly in RHAs) that had received NH during the first three weeks of life. With the exception of the SI test, the pattern of differences between female RHA vs. RLA profiles was overall consistent with what has previously been found in males of both strains, and NH treatment was able to enduringly improve some emotion-related and (spatial) cognitive outcomes in both strains.

Effects of low doses of the novel dehydroepiandrosterone (DHEA) derivative BNN27 in rat models of anxiety

RATIONALE

Several lines of evidence indicate that the neurosteroid dehydroepiandrosterone (DHEA) is involved in anxiety. BNN27 is a new DHEA derivative lacking steroidogenic effects. The beneficial effects exerted by BNN27 in preclinical models of schizophrenia and memory disorders have been recently reported.

OBJECTIVES

The present study was designed to investigate the effects of this DHEA novel analog on anxiety-like behavior in rats.

METHODS

To this end, the light/dark box, the open field, the contextual fear conditioning, and the excessive self-grooming induced by the serotonin 5-HT2c receptor agonist mCPP tests were utilized.

RESULTS

Animals treated acutely with BNN27 (1, 3, and 6 mg/kg) dose dependently spent more time in the bright compartment of the light/dark box and in the central zone of the open field with respect to their vehicle-treated cohorts. Further, BNN27 reduced freezing behavior and weakened the mCPP-induced excessive self-grooming.

CONCLUSIONS

Our data indicate that BNN27 is a highly potent anxiolytic agent, as in all studied paradigms it showed anxiolytic-like effects in male rats.

Transcranial direct current stimulation is more effective than pregabalin in controlling nociceptive and anxiety-like behaviors in a rat fibromyalgia-like model

OBJECTIVES

Despite the fact that fibromyalgia, a widespread disease of the musculoskeletal system, has no specific treatment, patients have shown improvement after pharmacological intervention. Pregabalin has demonstrated efficacy; however, its adverse effects may reduce treatment adherence. In this context, neuromodulatory techniques such as transcranial direct current stimulation (tDCS) may be employed as a complementary pain-relieving method. Consequently, the purpose of this study was to evaluate the effect of pregabalin and tDCS treatments on the behavioral and biomarker parameters of rats submitted to a fibromyalgia-like model.

METHODS

Forty adult male Wistar rats were divided into two groups: control and reserpine. Five days after the end of the administration of reserpine (1 mg/kg/3 days) to induce a fibromyalgia-like model, rats were randomly assigned to receive either vehicle or pregabalin (30 mg/kg) along with sham or active- tDCS treatments. The evaluated behavioral parameters included mechanical allodynia by von Frey test and anxiety-like behaviors by elevated plus-maze test (time spent in opened and closed arms, number of entries in opened and closed arms, protected head-dipping, unprotected head-dipping [NPHD], grooming, rearing, fecal boluses). The biomarker analysis (brain-derived neurotrophic factor [BDNF] and tumor necrosis factor-α [TNF-α]) was performed in brainstem and cerebral cortex and in serum.

RESULTS

tDCS reversed the reduction in the mechanical nociceptive threshold and the decrease in the serum BDNF levels induced by the model of fibromyalgia; however, there was no effect of pregabalin in the mechanical threshold. There were no effects of pregabalin or tDCS found in TNF-α levels. The pain model induced an increase in grooming time and a decrease in NPHD and rearing; while tDCS reversed the increase in grooming, pregabalin reversed the decrease in NPHD.

CONCLUSIONS

tDCS was more effective than pregabalin in controlling nociception and anxiety-like behavior in a rat model-like fibromyalgia. Considering the translational aspect, our findings suggest that tDCS could be a potential non-pharmacological treatment for fibromyalgia.

Prenatal allergic inflammation in rats confers sex-specific alterations to oxytocin and vasopressin innervation in social brain regions

Prenatal exposure to inflammation via maternal infection, allergy, or autoimmunity increases one's risk for developing neurodevelopmental and psychiatric disorders. Many of these disorders are associated with altered social behavior, yet the mechanisms underlying inflammation-induced social impairment remain unknown. We previously found that a rat model of acute allergic maternal immune activation (MIA) produced deficits like those found in MIA-linked disorders, including impairments in juvenile social play behavior. The neuropeptides oxytocin (OT) and arginine vasopressin (AVP) regulate social behavior, including juvenile social play, across mammalian species. OT and AVP are also implicated in neuropsychiatric disorders characterized by social impairment, making them good candidate regulators of social deficits after MIA. We profiled how acute prenatal exposure to allergic MIA changed OT and AVP innervation in several brain regions important for social behavior in juvenile male and female rat offspring. We also assessed whether MIA altered additional behavioral phenotypes related to sociality and anxiety. We found that allergic MIA increased OT and AVP fiber immunoreactivity in the medial amygdala and had sex-specific effects in the nucleus accumbens, bed nucleus of the stria terminalis, and lateral hypothalamic area. We also found that MIA reduced ultrasonic vocalizations in neonates and increased the stereotypical nature of self-grooming behavior. Overall, these findings suggest that there may be sex-specific mechanisms underlying MIA-induced behavioral impairment and underscore OT and AVP as ideal candidates for future mechanistic studies.

A subthalamo-parabrachial glutamatergic pathway is involved in stress-induced self-grooming in mice

Excessive self-grooming is an important behavioral phenotype of the stress response in rodents. Elucidating the neural circuit that regulates stress-induced self-grooming may suggest potential treatment to prevent maladaptation to stress that is implicated in emotional disorders. Stimulation of the subthalamic nucleus (STN) has been found to induce strong self-grooming. In this study we investigated the role of the STN and a related neural circuit in mouse stress-related self-grooming. Body-restraint and foot-shock stress-induced self-grooming models were established in mice. We showed that both body restraint and foot shock markedly increased the expression of c-Fos in neurons in the STN and lateral parabrachial nucleus (LPB). Consistent with this, the activity of STN neurons and LPB glutamatergic (Glu) neurons, as assessed with fiber photometry recording, was dramatically elevated during self-grooming in the stressed mice. Using whole-cell patch-clamp recordings in parasagittal brain slices, we identified a monosynaptic projection from STN neurons to LPB Glu neurons that regulates stress-induced self-grooming in mice. Enhanced self-grooming induced by optogenetic activation of the STN-LPB Glu pathway was attenuated by treatment with fluoxetine (18 mg·kg-1·d-1, p.o., for 2 weeks) or in the presence of a cage mate. Furthermore, optogenetic inhibition of the STN-LPB pathway attenuated stress-related but not natural self-grooming. Taken together, these results suggest that the STN-LPB pathway regulates the acute stress response and is a potential target for intervention in stress-related emotional disorders.

Distinct acute stressors exert an antagonistic effect on complex grooming during novelty habituation in rats

Grooming is a common readout in multiple rat models of neuropsychiatric diseases. It is usually associated with distress and negative emotionality, but also with emotional de-arousal after stress. These seemingly conflicting interpretations may result from specific grooming sequences appearing at different arousal levels and during distinct phases of the stress response. To further explore this hypothesis, we analyzed how distinct stressors affect grooming syntaxis and kinetics. To that end, we explored the independent and interacting effects of foot shocks, corticosterone (CORT), and novelty on exploratory activity, grooming, and ultrasonic vocalizations (USVs) in an open-field test (OF). Wistar rats were intraperitoneally injected either with vehicle or CORT, placed in a chamber where half of them were foot-shocked and then assessed in the OF. The next day, animals were re-exposed to the shock chamber and then tested in the OF without receiving any treatment. On day 1, foot shocks and -to a less extent CORT- increased freezing and inhibited rearing in the chamber, but only foot shocks increased distress USVs. In the OF, both treatments suppressed complex grooming, with foot-shocks also inhibiting exploration and CORT marginally reducing rearing. On day 2, foot-shocked rats showed conditioned fear when re-exposed to the chamber. When tested in the OF, foot-shocked and CORT-treated animals still showed low levels of complex grooming, with the former group also showing increased distress USVs. In this study, all different stressors inhibited complex grooming, suggesting an inverse association between these grooming subtypes and negative emotionality.

Color-Coding Method Reveals Enhancement of Stereotypic Locomotion by Phenazepam in Rat Open Field Test

One of the most important tasks in neuroscience is the search for theoretical foundations for the development of methods for diagnosing and treating neurological pathology, and for assessing the effect of pharmacological drugs on the nervous system. Specific behavioral changes associated with exposure to systemic influences have been invisible to the human eye for a long time. A similar pattern of changes is characteristic of phenazepam, a drug with a wide range of effects on the brain. In this study, we used a color-coding method, which consists of combining three time positions in one image, the present (0 s), the near future (0.33 s) and the far future (1.6 s). This method made it possible to identify movement patterns, such as the initialization of ahead movements, side turns and 180° turns (back), and also to determine the degree of predictability of future movements. The obtained data revealed a decrease in the number of turns to the sides while maintaining ahead movement, as well as an increase in the predictability of movements in rats under the influence of phenazepam. Thus, sedative doses of phenazepam do not exhibit general depression of brain functions, but the inhibition of specific centers, including the medial prefrontal cortex and postsubiculum, which are involved in stereotypic locomotive behavior.

Influences of roaming domestic cats on wildlife activity in patchy urban environments

Roaming domestic cats (Felis catus) are recognised as a threat to wildlife globally. Yet management of pet cats in urbanised areas is not regularly mandated, and management of feral cats in urbanised areas is rarely implemented. Mounting evidence emphasises the value of urban environments as hot spots of wildlife activity, which as the human population continues to grow may become the best or only habitats available to some wildlife species. Wildlife in urban environments must navigate introduced stressors that can compound with natural stressors. Additional, often novel, predators such as free-roaming pet and feral cats that are prevalent in urban environments could have high nonconsumptive fear/stress impacts on urban wildlife that influence their activity and adversely affect their health and reproduction capabilities, possibly more so than direct predation effects do. Cat roaming activity, particularly that of pet cats, could be managed with the support of the community, though motivation needs to be ensured. Understanding if roaming cat activity influences urban wildlife activity via perceived fear/stress impacts will help to build community motivation for the need for domestic cat management in urbanised areas. Using infrared motion sensor cameras positioned in both yards and green space edge habitats, we observed whether the presence and times active of native and introduced small mammals, and native birds, were impacted by domestic cat activity within a 24-h period and by their activity in the prior-24-h period. We found evidence of cat roaming activity during the hours of most wildlife activity, and show that wildlife navigated “landscapes of fear” relative to cat activity, as wildlife observed across a 24-h period increased their activity in the absence of cats in the same 24-h period and in the previous 24-h period. We also tested if cat activity was relative to previous cat activity, or disturbances, and found that cats reduced activity in response to each, but were still consistently present. Our results provide justification for the need to increase management of domestic cats in urbanised areas and offer fear/stress impacts as a novel approach to engender community support of such management.

Encore: Behavioural animal models of stress, depression and mood disorders

Animal studies over the past two decades have led to extensive advances in our understanding of pathogenesis of depressive and mood disorders. Among these, rodent behavioural models proved to be of highest informative value. Here, we present a comprehensive overview of the most popular behavioural models with respect to physiological, circuit, and molecular biological correlates. Behavioural stress paradigms and behavioural tests are assessed in terms of outcomes, strengths, weaknesses, and translational value, especially in the domain of pharmacological studies.

Effects of probiotic supplementation on very low dose AFB1-induced neurotoxicity in adult male rats

AIMS

Aflatoxin B1 (AFB1) is the most toxic and common form of AF found in food and feed. Although AFB1 exposure has toxic effects on many organs, studies on the brain are limited. Moreover, to the best of our knowledge, there is no study on the effect of probiotics on AFB1-induced neurotoxicity. Therefore, we aimed to evaluate the possible effects of probiotics on AFB1-induced neurotoxicity in the brain.

MAIN METHODS

Thirty-two adult male Wistar rats were divided into four groups: Vehicle (VEH), Probiotic (PRO) (2.5 × 10¹⁰ CFU/day VSL#3, orally), Aflatoxin B1 (AFB1) (25 μg/kg/week AFB1, orally), and Aflatoxin B1 + Probiotic (AFB1 + PRO) (2.5 × 10¹⁰ CFU/day VSL#3 + 25 μg/kg/week AFB1, orally). At the end of eight weeks, rats were behaviorally evaluated by the open field test, novel object recognition test, and forced swim test. Then, oxidative stress and inflammatory markers in brain tissues were analyzed. Next, brain sections were processed for Hematoxylin&Eosin staining and NeuN and GFAP immunostaining.

KEY FINDINGS

Probiotic supplementation tended to decrease oxidative stress and inflammatory markers compared to the AFB1 group. Besides, brain tissues had more normal histological structures in VEH, PRO, and AFB1 + PRO groups than in the AFB1 group. Moreover, in probiotic groups, GFAP immunoreactivity intensity was decreased, while NeuN-positive cell number increased in brain tissues compared to the AFB1 group.

SIGNIFICANCE

Probiotics seem to be effective at reducing the neurotoxic effects of AFB1. Thus, our study suggested that especially Bifidobacterium and Lactobacillus species can improve AFB1-induced neurotoxicity with their antioxidant and anti-inflammatory effects.

Ketamine administration in early postnatal life as a tool for mimicking Autism Spectrum Disorders core symptoms

Autism Spectrum Disorders (ASD) core symptoms include deficits of social interaction, stereotyped behaviours, dysfunction in language and communication. Beyond them, several additional symptoms, such as cognitive impairment, anxiety-like states and hyperactivity are often occurring, mainly overlapping with other neuropsychiatric diseases. To untangle mechanisms underlying ASD etiology, and to identify possible pharmacological approaches, different factors, such as environmental, immunological and genetic ones, need to be considered. In this context, ASD animal models, aiming to reproduce the wide range of behavioural phenotypes of this uniquely human disorder, represent a very useful tool. Ketamine administration in early postnatal life of mice has already been studied as a suitable animal model resembling psychotic-like symptoms. Here, we investigated whether ketamine administration, at postnatal days 7, 9 and 11, might induce behavioural features able to mimic ASD typical symptoms in adult mice. To this aim, we developed a 4-days behavioural tests battery, including Marble Burying, Hole Board, Olfactory and Social tests, to assess repetitive and stereotyped behaviour, social deficits and anxiety-like symptoms. Moreover, by using this mouse model, we performed neurochemical and biomolecular analyses, quantifying neurotransmitters belonging to excitatory-inhibitory pathways, such as glutamate, glutamine and gamma-aminobutyric acid (GABA), as well as immune activation biomarkers related to ASD, such as CD11b and glial fibrillary acidic protein (GFAP), in the hippocampus and amygdala. Possible alterations in levels of brain-derived neurotrophic factor (BDNF) expression in the hippocampus and amygdala were also evaluated. Our results showed an increase in stereotyped behaviours, together with social impairments and anxiety-like behaviour in adult mice, receiving ketamine administration in early postnatal life. In addition, we found decreased BDNF and enhanced GFAP hippocampal expression levels, accompanied by elevations in glutamate amount, as well as reduction in GABA content in amygdala and hippocampus. In conclusion, early ketamine administration may represent a suitable animal model of ASD, exhibiting face validity to mimic specific ASD symptoms, such as social deficits, repetitive repertoire and anxiety-like behaviour.

Something new and something blue: Responses to novelty in a rodent model of depression and epilepsy comorbidity

A bidirectional comorbidity exists between depression and epilepsy such that patients with epilepsy are at higher risk for developing depression, and vice versa. Each of these conditions individually can be complicated by behavioral effects that worsen quality of life, but less is known about these interactions within the comorbidity of depression and epilepsy. The SwLo rat has been selectively bred for depression-relevant behaviors and exhibits enhanced limbic seizure susceptibility. This study sought to characterize the effects of novelty and stress on the SwLo rodent model of this comorbidity. It was hypothesized that SwLo rats would exhibit altered responses to novelty, reflected in hyperactivity-, anxiety-, sensation seeking-, and/or compulsive behaviors, and that this would be exacerbated with stress. Compared to the SwHi rat (their depression- and epilepsy-resistant counterparts), SwLo rats showed increased entries in all areas of the Open Field Test and spent significantly more time in the light compartment of the Light-Dark Box. SwLo rats also had a significantly higher number of rearing behaviors in the inner squares of the Open Field Test, the closed arms of the Elevated Plus Maze, and both areas of the Light-Dark Box. They demonstrated increased Nestlet shredding but showed no difference in a marble burying task or in latency to consume food in a novelty suppressed feeding task. Interestingly, restraint stress showed little effect on these behaviors, despite increasing corticosterone levels. Combined, these results suggest an increase in exploratory sensation seeking and hypervigilant information-gathering behaviors in the SwLo rat that are not dependent on corticosterone levels. This shows the utility of this model for studying behavioral effects of comorbid depression and epilepsy and allows for their use in identifying underlying mechanisms or screening treatment strategies for this complex comorbidity.

Activation of the anterior cingulate cortex ameliorates anxiety in a preclinical model of fetal alcohol spectrum disorders

People with fetal alcohol spectrum disorders (FASD) are suffered from a wide range of interlinked cognitive and psychological problems. However, few therapeutic options are available for those patients due to limited dissection of its underlying etiology. Here we found that prenatal alcohol exposure (PAE) increases anxiety in mice due to a dysregulated functional connectivity between the anterior cingulate cortex (ACC) and basolateral amygdala (BLA). We also show that chemogenetic activation of excitatory neurons in the ACC reduced this anxiety behavior in the PAE mice. Interestingly, although the level of plasma corticosterone correlated with the increase in anxiety in the PAE, this level was not altered by chemogenetic activation of the ACC, suggesting that the functional connectivity between the ACC and the BLA does not alter the activity of the hypothalamic-pituitary-adrenal axis. Altogether, this study demonstrated that reduced excitation in the ACC is a cause of anxiety in the PAE mice, providing critical insights into the ACC-BLA neural circuit as a potential target for treating anxiety in FASD patients.

The neurotoxic effect of lactational PFOS exposure on cerebellar functional development in male mice

Recent studies showed a possible association between perfluorooctane sulfonate (PFOS) and developmental disabilities. We previously found the specific effects of PFOS exposure on learning and memory, however, its effect on the other developmental disabilities such as motor and social deficits remains unclear. We examined the effect of early lactational PFOS exposure on motor coordination, social activity, and anxiety in male mice. We orally administered a PFOS solution to dams from postnatal day 1-14. At 10 weeks old, we conducted a behavior test battery to evaluate motor performance, social activity, and anxiety, followed by electrophysiology and Western blot analysis. PFOS-exposed mice displayed impaired motor coordination. Whole-cell patch-clamp recordings from Purkinje cells revealed that the short-term and long-term plasticity at parallel fiber-Purkinje cell synapses are affected by PFOS exposure. Western blot analysis indicated that PFOS exposure increased syntaxin binding protein 1 (Munc18-1) and glutamate metabotropic receptor 1 (mGluR1) protein levels, which may be associated with the change in neurotransmitter release from parallel fibers and the level of long-term depression, respectively. The present study demonstrates that lactational PFOS exposure may have disrupted the pre- and postsynaptic plasticity at parallel fiber-Purkinje cell synapses, causing profound, long-lasting abnormal effects on the cerebellar function.

Wisket rat model of schizophrenia: Impaired motivation and, altered brain structure, but no anhedonia

It is well-known that the poor cognition in schizophrenia is strongly linked to negative symptoms, including motivational deficit, which due to, at least partially, anhedonia. The goal of this study was to explore whether the schizophrenia-like Wisket animals with impaired motivation (obtained in the reward-based hole-board test), also show decreased hedonic behavior (investigated with the sucrose preference test). While neurochemical alterations of different neurotransmitter systems have been detected in the Wisket rats, no research has been performed on structural changes. Therefore, our additional aim was to reveal potential neuroanatomical and structural alterations in different brain regions in these rats. The rats showed decreased general motor activity (locomotion, rearing and exploration) and impaired task performance in the hole-board test compared to the controls, whereas no significant difference was observed in the sucrose preference test between the groups. The Wisket rats exhibited a significant decrease in the frontal cortical thickness and the hippocampal area, and moderate increases in the lateral ventricles and cell disarray in the CA3 subfield of hippocampus. To our knowledge, this is the first study to investigate the hedonic behavior and neuroanatomical alterations in a multi-hit animal model of schizophrenia. The results obtained in the sucrose preference test suggest that anhedonic behavior might not be involved in the impaired motivation obtained in the hole-board test. The neuropathological changes agree with findings obtained in patients with schizophrenia, which refine the high face validity of the Wisket model.

Muscarinic regulation of self-grooming behavior and ultrasonic vocalizations in the context of open-field habituation in rats

Laboratory rats repeatedly exposed to an open field (OF) apparatus display increasingly high levels of grooming -especially that characterized by long and complex sequences- which has been taken as an additional index of novelty habituation. We hypothesized that disrupting such a learning process by administering an amnesic drug as the antimuscarinic scopolamine (SCP) could delay the appearance of more complex grooming subtypes. Thus, rats were pretreated either with SCP (15 mg/kg or 30 mg/kg) or vehicle (VEH) upon four one-day apart OF (OF1-4). On a fifth assessment, all rats received VEH to analyze the likely carry-over effect of SCP. Finally, we measured 50-kHz and 22-kHz ultrasonic vocalizations (USVs) as reliable markers of positive and negative emotionality, respectively. We found that SCP increased locomotion during OF1 and reduced rearing on OF1-OF4, causing no disruption in habituation over tests. SCP prevented the increase of total grooming time by inhibiting complex grooming subtypes and promoting short cephalic sequences. Despite the SCP-induced alterations on grooming agreed with our hypotheses, those changes may have resulted from a motor impairment that could have also affected rearing behavior. Additionally, SCP suppressed 50-kHz USVs while marginally increased 22-kHz calls. Once SCP was withdrawn, rearing, grooming, and some 50-kHz USVs subtypes returned to VEH levels, suggesting that novelty habituation occurred despite the SCP administration. Altogether, that mixed profile of SCP-induced behavioral changes may derive from the complex interplay between the contrasting action of SCP on different brain regions and the doses here used.

Salt as a non-caloric behavioral modifier: A review of evidence from pre-clinical studies

Though excess salt intake is well-accepted as a dietary risk factor for cardiovascular diseases, relatively little has been explored about how it impacts behavior, despite the ubiquity of salt in modern diets. Given the challenges of manipulating salt intake in humans, non-human animals provide a more tractable means for evaluating behavioral sequelae of high salt. By describing what is known about the impact of elevated salt on behavior, this review highlights how underexplored salt's behavioral effects are. Increased salt consumption in adulthood does not affect spontaneous anxiety-related behaviors or locomotor activity, nor acquisition of maze or fear tasks, but does impede expression of spatial/navigational and fear memory. Nest building is reduced by heightened salt in adults, and stress responsivity is augmented. When excess salt exposure occurs during development, and/or to parents, offspring locomotion is increased, and both spatial memory expression and social investigation are attenuated. The largely consistent findings reviewed here indicate expanded study of salt's effects will likely uncover broader behavioral implications, particularly in the scarcely studied female sex.

Medial prefrontal area reductions, altered expressions of cholecystokinin, parvalbumin, and activating transcription factor 4 in the corticolimbic system, and altered emotional behavior in a progressive rat model of type 2 diabetes

Metabolic disorders are associated with a higher risk of psychiatric disorders. We previously reported that 20-week-old Otsuka Long-Evans Tokushima fatty (OLETF) rats, a model of progressive type 2 diabetes, showed increased anxiety-like behavior and regional area reductions and increased cholecystokinin-positive neurons in the corticolimbic system. However, in which stages of diabetes these alterations in OLETF rats occur remains unclear. We aimed to investigate anxiety-like behavior and its possible mechanisms at different stages of type 2 diabetes in OLETF rats. Eight- and 30-week-old OLETF rats were used as diabetic animal models at the prediabetic and progressive stages of type 2 diabetes respectively, and age-matched Long-Evans Tokushima Otsuka rats served as non-diabetic controls. In the open-field test, OLETF rats showed less locomotion in the center zone and longer latency to leave the center zone at 8 and 30 weeks old, respectively. The areas of the medial prefrontal cortex were smaller in the OLETF rats, regardless of age. The densities of cholecystokinin-positive neurons in OLETF rats were higher in the lateral and basolateral amygdala only at 8 weeks old and in the anterior cingulate and infralimbic cortices and hippocampal cornu ammonis area 3 at both ages. The densities of parvalbumin-positive neurons of OLETF rats were lower in the cornu ammonis area 2 at 8 weeks old and in the prelimbic and infralimbic cortices at both ages. No apoptotic cell death was detected in OLETF rats, but the percentage of neurons co-expressing activating transcription factor 4 and cholecystokinin and parvalbumin was higher in OLETF rats at both ages in the anterior cingulate cortex and basolateral amygdala, respectively. These results suggest that altered emotional behavior and related neurological changes in the corticolimbic system are already present in the prediabetic stage of OLETF rats.

Low doses of ketamine and guanosine abrogate corticosterone-induced anxiety-related behavior, but not disturbances in the hippocampal NLRP3 inflammasome pathway

RATIONALE

Guanosine has been shown to potentiate ketamine's antidepressant-like actions, although its ability to augment the anxiolytic effect of ketamine remains to be determined.

OBJECTIVE

This study investigated the anxiolytic-like effects of a single administration with low doses of ketamine and/or guanosine in mice subjected to chronic administration of corticosterone and the role of NLRP3-driven signaling.

METHODS

Corticosterone (20 mg/kg, p.o.) was administered for 21 days, followed by a single administration of ketamine (0.1 mg/kg, i.p.), guanosine (0.01 mg/kg, p.o.), or ketamine (0.1 mg/kg, i.p.) plus guanosine (0.01 mg/kg, p.o.). Anxiety-like behavior and NLRP3-related targets were analyzed 24 h following treatments.

RESULTS

Corticosterone reduced the time spent in the open arms and the central zone in the elevated plus-maze test and open-field test, respectively. Corticosterone raised the number of unsupported rearings and the number and time of grooming, and decreased the latency to start grooming in the open-field test. Disturbances in regional distribution (increased rostral grooming) and grooming transitions (increased aborted and total incorrect transitions) were detected in corticosterone-treated mice. These behavioral alterations were accompanied by increased immunocontent of Iba-1, ASC, NLRP3, caspase-1, TXNIP, and IL-1β in the hippocampus, but not in the prefrontal cortex. The treatments with ketamine, guanosine, and ketamine plus guanosine were effective to counteract corticosterone-induced anxiety-like phenotype, but not disturbances in the hippocampal NLRP3 pathway.

CONCLUSIONS

Our study provides novel evidence that low doses of ketamine and/or guanosine reverse corticosterone-induced anxiety-like behavior and shows that the NLRP3 inflammasome pathway is likely unrelated to this response.

Physiological and Biochemical Markers of the Sex-Specific Sensitivity to Epileptogenic Factors, Delayed Consequences of Seizures and Their Response to Vitamins B1 and B6 in a Rat Model

The disturbed metabolism of vitamins B1 or B6, which are essential for neurotransmitters homeostasis, may cause seizures. Our study aims at revealing therapeutic potential of vitamins B1 and B6 by estimating the short- and long-term effects of their combined administration with the seizure inductor pentylenetetrazole (PTZ). The PTZ dose dependence of a seizure and its parameters according to modified Racine’s scale, along with delayed physiological and biochemical consequences the next day after the seizure are assessed regarding sexual dimorphism in epilepsy. PTZ sensitivity is stronger in the female than the male rats. The next day after a seizure, sex differences in behavior and brain biochemistry arise. The induced sex differences in anxiety and locomotor activity correspond to the disappearance of sex differences in the brain aspartate and alanine, with appearance of those in glutamate and glutamine. PTZ decreases the brain malate dehydrogenase activity and urea in the males and the phenylalanine in the females. The administration of vitamins B1 and B6 24 h before PTZ delays a seizure in female rats only. This desensitization is not observed at short intervals (0.5–2 h) between the administration of the vitamins and PTZ. With the increasing interval, the pyridoxal kinase (PLK) activity in the female brain decreases, suggesting that the PLK downregulation by vitamins contributes to the desensitization. The delayed effects of vitamins and/or PTZ are mostly sex-specific and interacting. Our findings on the sex differences in sensitivity to epileptogenic factors, action of vitamins B1/B6 and associated biochemical events have medical implications.

Global cerebral ischemia in adolescent male Long Evans rats: Effects of vanillic acid supplementation on stress response, emotionality, and visuospatial memory

The developmental period is critical in delineating plastic response to internal and external events. However, neurobehavioural effects of global cerebral ischemia (GCI) in the maturing brain remain largely unknown. This study characterised the effects of GCI experienced at puberty on adulthood (1) hippocampus CA1 neuronal damage, (2) cognitive and emotional impairments, and (3) glucocorticoid receptor (GR) expression. Effects of adolescent exposure to the phenol vanillic acid (VA) on post-ischemic outcomes were also determined. Male Long Evans rats (n = 35) were supplemented for 21 consecutive days (postnatal days 33-53) with VA (91 mg/kg) or nut paste vehicle (control) prior to a 10-min GCI or sham surgery. As adults, rats were tested in the Open Field Test (OFT), Elevated-Plus Maze (EPM), and Barnes Maze (BM). GR expression was determined in the basolateral amygdala (BLA), CA1, and paraventricular nucleus (PVN), and brain injury assessed via CA1 neuronal density. Adolescent GCI exposure induced extensive hippocampal CA1 injury, which was not prevented by VA supplementation. Behaviourally, GCI increased EPM exploration while having no impact on spatial memory. VA intake increased OFT peripheral exploration. Notably, while no delayed changes in CA1 and PVN GR immunoreactivity were noted, both treatments separately increased BLA GR expression when compared with sham-nut paste rats. Age at GCI occurrence plays a critical role on post-ischemic impairments. The observation of minimal functional impairments despite important CA1 neuronal damage supports use of compensatory mechanisms. Our findings also show daily VA supplementation during adolescence to have no protective effects on post-ischemic outcomes, contrasting adult intake.

Aging affects cognition and hippocampal ultrastructure in male Wistar rats

It is now well established that aging is associated with emotional and cognitive changes. Although the basis of such changes is not fully understood, ultrastructural alterations in key brain areas are likely contributing factors. Recently, we reported that aging-related anxiety in male Wistar rats is associated with ultrastructural changes in the central nucleus of amygdala, an area that plays important role in emotional regulation. In this study, we evaluated the cognitive performance of adolescent, adult, and aged male Wistar rats in multi-branch maze (MBM) as well as in Morris water maze (MWM). We also performed ultrastructural analysis of the CA1 region of the hippocampus, an area intimately involved in cognitive function. The behavioral data indicate significant impairments in few indices of cognitive functions in both tests in aged rats compared to the other two age groups. Concomitantly, a total number of presynaptic vesicles as well as vesicles in the resting pool were significantly lower, whereas postsynaptic mitochondrial area was significantly higher in aged rats compared to the other age groups. No significant differences in presynaptic terminal area or postsynaptic mitochondrial number were detected between the three age groups. These results indicate that selective ultrastructural changes in specific hippocampal region may accompany cognitive decline in aging rats.

Aberrant Early in Life Stimulation of the Stress-Response System Affects Emotional Contagion and Oxytocin Regulation in Adult Male Mice

Results over the last decades have provided evidence suggesting that HPA axis dysfunction is a major risk factor predisposing to the development of psychopathological behaviour. This susceptibility can be programmed during developmental windows of marked neuroplasticity, allowing early-life adversity to convey vulnerability to mental illness later in life. Besides genetic predisposition, also environmental factors play a pivotal role in this process, through embodiment of the mother's emotions, or via nutrients and hormones transferred through the placenta and the maternal milk. The aim of the current translational study was to mimic a severe stress condition by exposing female CD-1 mouse dams to abnormal levels of corticosterone (80 µg/mL) in the drinking water either during the last week of pregnancy (PreCORT) or the first one of lactation (PostCORT), compared to an Animal Facility Rearing (AFR) control group. When tested as adults, male mice from PostCORT offspring and somewhat less the PreCORT mice exhibited a markedly increased corticosterone response to acute restraint stress, compared to perinatal AFR controls. Aberrant persistence of adolescence-typical increased interest towards novel social stimuli and somewhat deficient emotional contagion also characterised profiles in both perinatal-CORT groups. Intranasal oxytocin (0 or 20.0 µg/kg) generally managed to reduce the stress response and restore a regular behavioural phenotype. Alterations in density of glucocorticoid and mineralocorticoid receptors, oxytocin and µ- and κ-opioid receptors were found. Changes differed as a function of brain areas and the specific age window of perinatal aberrant stimulation of the HPA axis. Present results provided experimental evidence in a translational mouse model that precocious adversity represents a risk factor predisposing to the development of psychopathological behaviour.

Vigilance: discussion of related concepts and proposal for a definition

We reviewed current definitions of vigilance to propose a definition, applicable in sleep medicine. As previous definitions contained terms such as attention, alertness, and arousal, we addressed these concepts too. We defined alertness as a quantitative measure of the mind state governing sensitivity to stimuli. Arousal comprises a stimulus-induced upward change in alertness, irrespective of the subsequent duration of the increased level of alertness. Vigilance is defined as the capability to be sensitive to potential changes in one's environment, ie the capability to reach a level of alertness above a threshold for a certain period of time rather than the state of alertness itself. It has quantitative and temporal dimensions. Attention adds direction towards a stimulus to alertness, requiring cognitive control: it involves being prepared to process stimuli coming from an expected direction. Sustained attention corresponds to a state in which some level of attention is purposefully maintained, adding a time factor to the definition of attention. Vigilance differs from sustained attention in that the latter in addition implies a direction to which attention is cognitively directed as well as a specification of duration. Attempts to measure vigilance, however, are often in fact measurements of sustained attention.

Decreased social interaction in the RHA rat model of schizophrenia-relevant features: Modulation by neonatal handling

The Roman-Low (RLA) and High-Avoidance (RHA) rat strains have been bidirectionally selected and bred, respectively, for extremely poor vs. rapid acquisition of the two-way active avoidance task. Over 50 years of selective breeding have led to two strains displaying many differential specific phenotypes. While RLAs display anxious-related behaviours, RHA rats show impulsivity, and schizophrenia-like positive and cognitive symptoms or phenotypes. Neonatal handling (NH) is an environmental treatment with long-lasting anxiolytic-like and anti-stress effects. NH also reduces symptoms related to schizophrenia, such as pre-pulse inhibition (PPI) impairment and latent inhibition (LI) deficits, and improves spatial working memory and cognitive flexibility. The present work was aimed at exploring whether RHAs also display negative schizophrenia-like symptoms (or phenotypes), such as lowered preference for social interaction (i.e. asociality), and whether NH would reduce these deficits. To this aim, we evaluated naïve inbred RHA and RLA rats in a social interaction (SI) test after either long- or short-term habituation to the testing set up (studies 1-2). In Study 3 we tested untreated and NH-treated RHA and RLA rats in novel object exploration (NOE) and SI tests. Compared with RHAs, RLA rats displayed increased anxiety-related behaviours in the NOE (i.e. higher behavioural inhibition, lesser exploration of the novel object) and SI (i.e. higher levels of self-grooming) tests which were dramatically reduced by NH treatment, thus supporting the long-lasting anxiolytic-like effect of NH. Remarkably, RHA rats showed decreased social preference in the SI test compared with RLAs, evidencing that RHAs would present a relative asociality, which is thought to model some negative symptomatology (i.e. social withdrawal) of schizophrenia. NH increased absolute levels of social behaviour in both strains, but with a more marked effect in RHA rats, especially in the first 5 min of the SI test. Thus, it is hypothesized that, apart from its effects on anxiety-related behaviours, NH might have long-lasting positive effects on behavioural and neurobiological processes that are impaired in schizophrenia.

The cage test as an easy way to screen and evaluate spontaneous activity in preclinical neuroscience studies

Within behavioral neuroscience, subjects used to be randomly assigned to the experimental groups based on the premise that interindividual variability will be homogeneously distributed. However, the equivalence offered by randomization diminishes in small samples, which is the case for most experiments in the field. In rodents, it is well-recognized that individual differences in psychomotor reactivity, risk-assessment behaviors, and emotional responsiveness modulate the effects of different pharmacological and non-pharmacological treatments. For that reason, knowing such differences before the experiment provides highly valuable information for balancing the groups so that the interindividual variability is equally distributed within the groups without excluding subjects as far as possible. Because unconditioned anxiety tests such as the open-field (OF) and the elevated plus-maze are commonly used within experimental procedures, we developed a strategy to explore the rat's behavioral phenotype by assessing it in a very innocuous testing context: a housing cage.•We offer a very straightforward protocol for assessing spontaneous, novelty-induced reactivity in rodents.•We describe its implementation, analysis, and use, as well as some suggestions about key behavioral readouts for the group allocation procedure.•The current protocol provides an alternative strategy to assess a reasonably wide range of behavioral outcomes, most of which are of great interest in modeling different neuropsychiatric disorders.

Neural Mechanisms Underlying Repetitive Behaviors in Rodent Models of Autism Spectrum Disorders

Autism spectrum disorder (ASD) is comprised of several conditions characterized by alterations in social interaction, communication, and repetitive behaviors. Genetic and environmental factors contribute to the heterogeneous development of ASD behaviors. Several rodent models display ASD-like phenotypes, including repetitive behaviors. In this review article, we discuss the potential neural mechanisms involved in repetitive behaviors in rodent models of ASD and related neuropsychiatric disorders. We review signaling pathways, neural circuits, and anatomical alterations in rodent models that display robust stereotypic behaviors. Understanding the mechanisms and circuit alterations underlying repetitive behaviors in rodent models of ASD will inform translational research and provide useful insight into therapeutic strategies for the treatment of repetitive behaviors in ASD and other neuropsychiatric disorders.

Acute stress differentially affects grooming subtypes and ultrasonic vocalisations in the open-field and home-cage test in rats

Grooming behaviour in rodents has been associated with emotional distress, especially in unfamiliar and aversive contexts. However, the biological function of grooming in such situations is still unclear. We hypothesised that particular grooming subtypes are differentially associated with the stress response. Here, we investigated the effects of an acute stress exposure on grooming and ultrasonic vocalisations (USVs) assessed on different testing contexts varying in the level of familiarity. To this aim, footshocked and non-footshocked rats were tested for 20 min on one of the following conditions: an unfamiliar open-field test, a familiar open-field test, and an individual home cage filled with bedding. We found that footshock stress slightly decreased complex grooming sequences while increased cephalic grooming. Stress induced a negative affective state inferred from an increase and decrease of 22-kHz and 50-kHz calls, respectively. The latter USVs correlated positively with the complex grooming subtypes. Altogether, a detailed analysis of grooming seems necessary for elucidating its diverse biological functions. Nevertheless, footshock stress and testing conditions produced weaker-than-expected effects, possibly because the time elapsed between footshocks and behavioural testing was too short for eliciting a full stress response, and because the simple footshock-chamber experience may have impeded detecting stronger effects of familiarity.

Neurobehavioral Effects of Restricted and Unpredictable Environmental Enrichment in Rats

To study how motivational factors modulate experience-dependent neurobehavioral plasticity, we modify a protocol of environmental enrichment (EE) in rats. We assumed that the benefits derived from EE might vary according to the level of incentive salience attributed to it. To enhance the rewarding properties of EE, access to the EE cage varied randomly from 2 to 48 h for 30 days (REE). The REE group was enriched only 50% of the time and was compared to standard housing and continuous EE (CEE) groups. As behavioral readout, we analyzed the spontaneous activity and the ultrasonic vocalizations (USVs) within the EE cage weekly, and in the open field test at the end of the experiment. In the cage, REE increased the utilization of materials, physical activity, and the rate of appetitive USVs. In the OF, the CEE-induced enhancements in novelty habituation and social signaling were equaled by the REE. At the neural level, we measured the expression of genes related to neural plasticity and epigenetic regulations in different brain regions. In the dorsal striatum and hippocampus, REE upregulated the expression of the brain-derived neurotrophic factor, its tropomyosin kinase B receptor, and the DNA methyltransferase 3A. Altogether, our results suggest that the higher activity within the cage and the augmented incentive motivation provoked by the REE boosted its neurobehavioral effects equaling or surpassing those observed in the CEE condition. As constant exposures to treatments or stimulating environments are virtually impossible for humans, restricted EE protocols would have greater translational value than traditional ones.

Early postnatal hypoxia induces behavioral deficits but not morphological damage in the hippocampus in adolescent rats

Hypoxia is one of the major pathological factors affecting brain function. The aim of the present study was to describe the effect of neonatal hypobaric hypoxia on the behavior of rats and to analyze its effect on hippocampal neurodegeneration. Hypobaric hypoxia at a simulated altitude of 9000 m was induced for one hour in neonatal rat pups (PND7 and PND9) of both sexes. Subsequently, the rats underwent behavioral testing on PND25 and PND35 using a LABORAS apparatus to assess spontaneous behavior. Hypoxia did not cause any morphological damage in the hippocampus of rats. However, hypoxia on PND7 led to less horizontal locomotor activity both, in males (on PND25) and females (on PND35). Hypoxia on PND9 led to higher rearing in females on PND25. Hypoxic males exhibited higher grooming activity, while females lower grooming activity on PND35 following hypoxia induced on PND7. In females, hypoxia on PND9 resulted in higher grooming activity on PND25. Sex differences in the effect of hypoxia was observed on PND35, when hypoxic males compared to hypoxic females displayed more locomotor, rearing and grooming activity. Our data suggest that hypoxia on PND7 versus PND9 differentially affects locomotion and grooming later in adolescence and these effects are sex-dependent.