Isolation Rearing Research Articles

Time-Dependent Effects of Buspirone versus Desipramine on the 5-Choice Serial Reaction Time Task in Rats Reared in Social Isolation: Implication of Early Life Experience and Motoric Impulsivity.

Early life social experience and the function of the central serotonin (5-Hydroxytryptophan, 5-HT) system are involved in development of behavioral impulsivity in which individuals act without forethought or before all necessary information is available. However, most of the evidence has been obtained from acute 5-HT manipulation, whereas, the present study aimed to investigate the effects of subchronic regimen targeting of 5-HT1A receptors on motoric waiting impulsivity in socially isolated rats. A two-week protocol of buspirone (0.5 mg/kg/day) and desipramine (2.5 mg/kg/day) was employed for rats following social isolation rearing (IR) to examine their behavioral performance in a 5-choice serial reaction time task (5-CSRTT) during the treatment regimen. Responses in any one of the apertures prior to an informative signal were recorded as a premature response. IR rats presented with more locomotor activity than socially reared (SR) rats. Buspirone progressively increased the baseline level of premature responding in a time-dependent manner that was not observed in IR rats. Both IR and SR rats exhibited less premature responding following acute buspirone challenge. For a subchronic desipramine regimen, IR rats followed the same trend of SR controls to increase the prematurity of baseline response. Buspirone but not desipramine-induced time-dependent effects of motoric waiting impulsivity can be reversed by IR, indicating a role for early life social experience on 5-HT1A receptor-associated ability to control impulsiveness.

Modulation of cognition and neuronal plasticity in gain- and loss-of-function mouse models of the schizophrenia risk gene Tcf4

The transcription factor TCF4 was confirmed in several large genome-wide association studies as one of the most significant schizophrenia (SZ) susceptibility genes. Transgenic mice moderately overexpressing Tcf4 in forebrain (Tcf4tg) display deficits in fear memory and sensorimotor gating. As second hit, we exposed Tcf4tg animals to isolation rearing (IR), chronic social defeat (SD), enriched environment (EE), or handling control (HC) conditions and examined mice with heterozygous deletion of the exon 4 (Tcf4Ex4δ+/−) to unravel gene-dosage effects. We applied multivariate statistics for behavioral profiling and demonstrate that IR and SD cause strong cognitive deficits of Tcf4tg mice, whereas EE masked the genetic vulnerability. We observed enhanced long-term depression in Tcf4tg mice and enhanced long-term potentiation in Tcf4Ex4δ+/− mice indicating specific gene-dosage effects. Tcf4tg mice showed higher density of immature spines during development as assessed by STED nanoscopy and proteomic analyses of synaptosomes revealed concurrently increased levels of proteins involved in synaptic function and metabolic pathways. We conclude that environmental stress and Tcf4 misexpression precipitate cognitive deficits in 2-hit mouse models of relevance for schizophrenia.

Effects of early life social experience on fear extinction and related glucocorticoid profiles – behavioral and neurochemical approaches in a rat model of PTSD

People may agonize over an intrusive fear-inducing memory even when the traumatic event has passed, which is the principle manifestation of posttraumatic stress disorder (PTSD). However, many traumatized people do not present symptoms of PTSD, implying that certain hidden factors help those individuals to cope with the traumatic stress. Increasing evidence suggests that early life experience may serve as a predisposing factor in the development of PTSD. For example, early life social deprivation disrupts the glucocorticoid system, one of the biological abnormalities of PTSD. By employing isolation rearing (IR) with a subsequent single prolonged stress (SPS) paradigm, we examined the hypothesis that early-life social experience may change the outcome of traumatic stress in both behavioral and neurochemical profiles. Behaviorally, the performance of rats on a Pavlovian fear conditioning test was measured to evaluate their retrieval ability of fear memory extinction. Neurochemically, plasma corticosterone levels and glucocorticoid receptor (GR), FK506-binding proteins 4 and 5 (FKBP4 and FKBP5) and early growth response-1 (Egr-1) expression were measured in GR-abundant brain areas, including the hypothalamus, medial prefrontal cortex, and hippocampus. Our results demonstrated an area-dependent IR effect on the SPS outcomes. IR prevented the SPS-impaired fear extinction retrieval ability and averted the SPS-elevated expression of GR, FKBP4, and Egr-1 in the hippocampus, whereas it did not change the SPS-reduced plasma corticosterone levels and SPS-enhanced GR activity in the mPFC and hypothalamus. The present study provides some new insights to support the hypothesis that early-life experience may play a role in the occurrence of PTSD.

Early life social experience affects adulthood fear extinction deficit and associated dopamine profile abnormalities in a rat model of PTSD

Individuals may develop fear extinction deficits after life-threatening traumatic events; such deficits indicate posttraumatic stress disorder (PTSD). Because the occurrence of this disorder differs among people who have experienced trauma, hidden underlying factors should be determined. Increasing evidence suggests the involvement of neuronal dysregulation of information processes or cognitive function during development. This neuronal dysregulation is caused by disturbances in dopamine (DA) transmission within the fear circuit, which comprises the medial prefrontal cortex (mPFC), amygdala, and hippocampus. Single prolonged stress (SPS) combined with an isolation rearing (IR) paradigm was used to randomly assign rats to four groups [social rearing–no SPS (SR-NS), SR-SPS, IR-NS, and IR-SPS], and their performance in prepulse inhibition (PPI) and on Pavlovian fear conditioning tests was assessed. Tissue DA levels and the expression of DA receptors (D1R and D2R) in the fear circuit were measured at the end of the experiment. Our results indicated that PPI deficits and fear extinction problems were specific to rats subjected to IR and SPS, respectively. Furthermore, IR-induced PPI deficits were not influenced by SPS, but SPS-induced fear extinction retrieval impairment could be adjusted according to previous IR experiences. Neurochemically, tissue DA levels and D1R expression in the mPFC and amygdala were nonspecifically reduced by IR and SPS, whereas D2R expression in the mPFC and amygdala was higher in IR-SPS than in SR-SPS rats. These findings suggest that early life experiences may influence fear responses in adulthood through a change in DA profiles within the fear circuit.

Rosuvastatin improves olanzapine’s effects on behavioral impairment and hippocampal, hepatic and metabolic damages in isolated reared male rats

Background & aimSchizophrenia is a chronic, disabling neurological illness. This study investigated the effect of rosuvastatin (RSU) addition to the antipsychotic drug: olanzapine (OLZ) in treatment of post-weaning isolation rearing (IR) damaging effect and assessed behavioral impairment, metabolic and hepatic abnormalities, oxidative stress, and inflammatory markers. MethodsTreatment with OLZ (6 mg/kg, P.O.) and/or RSU (10 mg/kg, I.P.) have been started 6 weeks after isolation. We assessed behavioral tests, serum cortisol level, and hippocampal content of neurotransmitters. In addition, we assessed histopathology, inflammatory and oxidative stress markers of hippocampus, liver and adipose tissue ResultsTreatment of IR animals with OLZ, and/or RSU significantly counteracted the changes in hippocampus, liver and adipose tissue induced by post-weaning IR. Co-treatment of IR rats with both OLZ and RSU showed additive effects in some areas like improving both tumor necrosis factor alpha (TNFα) in both hippocampus and liver, histopathology of liver, oxidative stress markers of adipose tissue, β3 adrenergic receptors (ADRβ3), serum cortisol and total cholesterol. In addition, RSU alone alleviated the damage of IR rats by the same efficacy as OLZ with more benefit in cognition and exploration. Conclusionpost-weaning IR as a model has behavioral, hippocampal, hepatic and marked metabolic changes more relevant to schizophrenia than drug-induced models. These effects were ameliorated by RSU and/or OLZ that are explained by their antioxidant, anti-inflammatory, anti-stress and anti-hyperlipidemic properties. Interestingly, co-treatment with both drugs showed a better effect.

Enhancement of Aggression Induced by Isolation Rearing is Associated with a Lack of Central Serotonin.

Isolation rearing (IR) enhances aggressive behavior, and the central serotonin (5-hydroxytryptamine, 5-HT) system has been linked to IR-induced aggression. However, whether the alteration of central serotonin is the cause or consequence of enhanced aggression is still unknown. In the present study, using mice deficient in central serotonin Tph2-/- and Lmx1b-/-, we examined the association between central serotonin and aggression with or without social isolation. We demonstrated that central serotonergic neurons are critical for the enhanced aggression after IR. 5-HT depletion in wild-type mice increased aggression. On the other hand, application of 5-HT in Lmx1b-/- mice inhibited the enhancement of aggression under social isolation conditions. Dopamine was downregulated in Lmx1b-/- mice. Similar to 5-HT, L-DOPA decreased aggression in Lmx1b-/- mice. Our results link the serotoninergic system directly to aggression and this may have clinical implications for aggression-related human conditions.

Postweaning Isolation Rearing Alters the Adult Social, Sexual Preference and Mating Behaviors of Male CD-1 Mice.

Objective: No study has comprehensively evaluated the effect of postweaning isolation on the social and sexual behaviors of a certain strain of rodents in ethology. The present study aims to explore how and to what extent isolation rearing after postweaning affects the social and sexual behaviors of male CD-1 mice in adulthood systematically.Methods: Male CD-1 mice were randomly assigned to two groups: isolation reared (IS, one mouse per cage, n = 30) and group housed (GH, five mice per cage, n = 15). The mice underwent isolation rearing from postnatal day 23 to day 93. Then, social affiliation, recognition and memory were measured through selection task experiments. Social interaction under a home cage and novel environment were measured via resident–intruder and social interaction test, respectively. Furthermore, sexual preference, homosexual and heterosexual behaviors were measured.Results: Our study found that postweaning isolation increased the social affiliation for conspecifics (p = 0.001), reduced social recognition (p = 0.042) and impaired social memory. As for social interaction, isolated mice showed a remarkably increased aggression toward the intruder male in a home cage or novelty environment. For instance, isolated mice presented a short attack latency (p < 0.001), high attack frequency (p < 0.001) and long attack duration (p < 0.001). In addition, isolated mice exhibited further social avoidance. Contrastingly, isolated mice displayed a reduced sexual preference for female (IS: 61.47 ± 13.80%, GH: 70.33 ± 10.06%, p = 0.038). As for heterosexual behavior, isolated mice have a short mating duration (p = 0.002), long mounting latency (p = 0.002), and long intromission latency (p = 0.015). However, no association was observed between postweaning isolation and homosexual behavior in male CD-1 mouse.Conclusion: Postweaning isolation increased the social affiliation, impaired the social cognition and considerably increased the aggression in social interaction of adult male CD-1 mice. Postweaning isolation induced a decreased sexual preference for female in adulthood. Postweaning isolation extended the latency to mate, thereby reducing mating behavior. No association was observed between isolation and homosexual behavior.

Transcriptomic analysis reveals oxidative phosphorylation activation in an adolescent social isolation rat model

Complex interactions between genetic and environmental factors exert a sustained influence on the pathogenesis of schizophrenia (SCZ). Adolescent social isolation is regarded as a typical paradigm for SCZ. However, the underlying pathological mechanisms are not fully understood. In this study, adolescent Sprague-Dawley (SD) rats were placed in isolation rearing (IR) or social rearing (SR) conditions from postnatal day (PND) 21 to 34 to establish a SCZ disease model and a control model, respectively. Prepulse inhibition (PPI) assays and elevated plus maze tests were performed on PND 56. Next, prefrontal cortex (PFC) tissues were isolated for transcriptomic sequencing and RT-qPCR analyses. The results indicated that adolescent social isolation induced anxious behaviors and disrupted PPIs as well as specific PFC gene expression patterns in adult SD rats. A total of 196 genes were identified as upregulated, and 748 genes were identified as down-regulated in the IR group compared with those in the SR group. Differentially expressed genes (DEGs) were highly enriched in the KEGG pathways associated with the comorbidity of neurological disorder and oxidative phosphorylation (OXPHOS); 26 out of 27 comorbid neurological disorder-associated DEGs overlapped with 31 OXPHOS-associated DEGs. Those 26 overlapping DEGs were all upregulated in the IR group and could easily distinguish the IR group from the SR group; 6 of these DEGs (COX7C, NDUFB11, NDUFA2, NDUFC2, ATP5C1, and COX6A1) were verified by RT-qPCR. Here, we provide a systematic overview of gene expression alterations in adolescent-social-isolation-induced SCZ (ASI-SCZ), which suggests that genes that are associated with the comorbidity of neurological disorders, especially OXPHOS-related genes, contribute to the pathogenesis of ASI-SCZ.

Adolescent isolation rearing produces a prepulse inhibition deficit correlated with expression of the NMDA GluN1 subunit in the nucleus accumbens.

Adolescence is a transition period during which social interaction is necessary for normal brain and behavior development. Severely abnormal social interactions during adolescence can increase the incidence of lifelong psychiatric disease. Decreased prepulse inhibition (PPI) is a quantifiable hallmark of some psychiatric illnesses in humans and can be elicited in rodents by isolation rearing throughout the adolescent transition period. PPI is a measure of sensorimotor gating in which the nucleus accumbens (Acb) is crucially involved. The Acb is comprised of core and shell subregions, which receive convergent dopaminergic and glutamatergic inputs. To gain insight into the neurobiological correlates of adolescent adversity, we conducted electron microscopic immunolabeling of dopamine D1 receptors (D1Rs) and the GluN1 subunit of glutamate NMDA receptors in the Acb of isolation-reared (IR) adult male rats. In all animals, GluN1 was primarily located in dendritic profiles, many of which also contained D1Rs. GluN1 was also observed in perisynaptic glia and axon terminals. In IR rats compared with group-reared controls, GluN1 density was selectively decreased in D1R-containing dendrites of the Acb core. Across all animals, dendritic GluN1 density correlated with average percent PPI, implicating endogenous expression of NMDA receptors of the Acb as a possible substrate of the PPI response. These results suggest that adolescent isolation dampens NMDA-mediated excitation in direct (D1R-containing) output neurons of the Acb, and that these changes influence the operational measure of PPI.

\u2018Waiting impulsivity\u2019 in isolation-reared and socially-reared rats: effects of amphetamine

BackgroundRats reared in social isolation exhibit various cognitive and behavioural abnormalities in adulthood. However, impulsivity following this treatment still remains unclear, especially in response to medications used in attention deficit hyperactivity disorder, such as amphetamine.MethodsUsing an isolation-rearing (IR) manipulation, the present study examined the effects of IR on impulsive action and impulsive choice when also treated with doses of d-amphetamine, by employing the five-choice serial reaction time task (5-CSRTT) and a temporal discounting of reward task (TDRT), respectively.ResultsIR rats showed similar acquisition of the 5-CSRTT. Amphetamine increased premature responding in both groups; however, IR rats showed less responding overall. For the TDRT, IR rats revealed a greater preference for the large but delayed reward during task acquisition (i.e. were less impulsive) with a higher rate of nose poking during the delay, and exhibited a compressed dose-response function (i.e. reduced dose sensitivity) for amphetamine.DiscussionImpulsive action and impulsive choice were reduced in IR rats under certain conditions, and a blunted response to d-amphetamine was found on these measures. These reductions in impulsivity contrast with locomotor hyperactivity normally shown in IR rats and the findings have implications for the utility of IR as a model of psychopathology.

Importance of intervention timing in the effectiveness of antipsychotics

The use of early pharmacological intervention in treating young patients with schizophrenia is a debating issue for psychiatrists. However, on the basis of developmental theory, early antipsychotic intervention can be beneficial in terms of protecting neurons from further deterioration. This study investigated whether the initiation of second-generation antipsychotic (SGA) treatment at a younger age can effectively reverse schizophrenia-relevant behavioral and neurochemical features, namely acoustic prepulse inhibition (PPI) and accumbal dopamine (DA) efflux, respectively. Risperidone (RIS, 1mg/kg/day) or olanzapine (OLA, 2.5mg/kg/day) was administered for 6weeks in rats subjected to isolation rearing (IR) in adolescence or young adulthood. Behavioral testing was performed at 3 and 5 (for locomotor activity) and 2 and 4 (for PPI) weeks after the initiation of the pharmacological regimen. An additional PPI test was performed 6weeks after the initiation of the pharmacological regimen to assess the acute add-on effect of RIS or OLA. Dopamine (DA) efflux of the nucleus accumbens was evaluated through in vivo microdialysis at the end of the study, for measuring both the baseline levels after the chronic regimen and the responsiveness to acute add-on RIS or OLA treatment. Our results demonstrated that the effects of SGAs on PPI and accumbal DA efflux were dissociated. Specifically, RIS intervention was more beneficial for adolescent than young adult IR rats in restoring their PPI deficit, whereas OLA was age-independently effective in stimulating the accumbal DA efflux. Both PPI and accumbal DA could be employed to reflect IR-induced abnormalities, in which accumbal DA appeared to be more suitable in depicting the long-term effect of IR, whereas PPI might be a more accurate biological index for revealing the advantages of early RIS intervention.

Early Life Stress Increases Metabolic Risk, HPA Axis Reactivity, and Depressive-Like Behavior When Combined with Postweaning Social Isolation in Rats

Early-life stress is associated with depression and metabolic abnormalities that increase the risk of cardiovascular disease and diabetes. Such associations could be due to increased glucocorticoid levels. Periodic maternal separation in the neonate and rearing in social isolation are potent stressors that increase hypothalamus-pituitary-adrenal axis activity. Moreover, social isolation promotes feed intake and body weight gain in rats subjected to periodic maternal separation; however, its effects on metabolic risks have not been described. In the present study, we evaluated whether periodic maternal separation, social isolation rearing, and a combination of these two stressors (periodic maternal separation + social isolation rearing) impair glucose homeostasis and its relation to the hypothalamus-pituitary-adrenal axis and depressive-like behavior. Periodic maternal separation increased basal corticosterone levels, induced a passive coping strategy in the forced swimming test, and was associated with a mild (24%) increase in fasting glucose, insulin resistance, and dyslipidemia. Rearing in social isolation increased stress reactivity in comparison to both controls and in combination with periodic maternal separation, without affecting the coping strategy associated with the forced swimming test. However, social isolation also increased body weight gain, fasting glucose (120%), and insulin levels in rats subjected to periodic maternal separation. Correlation analyses showed that stress-induced effects on coping strategy on the forced swimming test (but not on metabolic risk markers) are associated with basal corticosterone levels. These findings suggest that maternal separation and postweaning social isolation affect stress and metabolic vulnerability differentially and that early-life stress-related effects on metabolism are not directly dependent on glucocorticoid levels. In conclusion, our study supports the cumulative stress hypothesis, which suggests that metabolic risk markers arise when vulnerable individuals are exposed to social challenges later in life.

Divergent effects of isolation rearing on prepulse inhibition, activity, anxiety and hippocampal-dependent memory in Roman high- and low-avoidance rats: A putative model of schizophrenia-relevant features

Social isolation of rats induces a constellation of behavioral alterations known as “isolation syndrome” that are consistent with some of the positive and cognitive symptoms observed in schizophrenic patients. In the present study we have assessed whether isolation rearing of inbred Roman high-avoidance (RHA-I) and Roman low-avoidance (RLA-I) strains can lead to the appearance of some of the key features of the “isolation syndrome”, such as prepulse inhibition (PPI) deficits, increased anxious behavior, hyperactivity and memory/learning impairments. Compared to RLA-I rats, the results show that isolation rearing (IR) in RHA-I rats has a more profound impact, as they exhibit isolation-induced PPI deficits, increased anxiety, hyperactivity and long-term reference memory deficits, while isolated RLA-I rats only exhibit deficits in a spatial working memory task. These results give further support to the validity of RHA-I rats as a genetically-based model of schizophrenia relevant-symptoms.

Isolation Rearing Reduces Neuronal Excitability in Dentate Gyrus Granule Cells of Adolescent C57BL/6J Mice: Role of GABAergic Tonic Currents and Neurosteroids.

Early-life exposure to stress, by impacting on a brain still under development, is considered a critical factor for the increased vulnerability to psychiatric disorders and abuse of psychotropic substances during adulthood. As previously reported, rearing C57BL/6J weanling mice in social isolation (SI) from their peers for several weeks, a model of prolonged stress, is associated with a decreased plasma and brain levels of neuroactive steroids such as 3α,5α-THP, with a parallel up-regulation of extrasynaptic GABAA receptors (GABAAR) in dentate gyrus (DG) granule cells compared to group-housed (GH) mice. In the present study, together with the SI-induced decrease in plasma concentration of both progesterone and 3α,5α-THP, and an increase in THIP-stimulated GABAergic tonic currents, patch-clamp analysis of DG granule cells revealed a significant decrease in membrane input resistance and action potential (AP) firing rate, in SI compared to GH mice, suggesting that SI exerts an inhibitory action on neuronal excitability of these neurons. Voltage-clamp recordings of glutamatergic spontaneous excitatory postsynaptic currents (sEPSCs) revealed a SI-associated decrease in frequency as well as a shift from paired-pulse (PP) depression to PP facilitation (PPF) of evoked EPSCs, indicative of a reduced probability of glutamate release. Daily administration of progesterone during isolation reverted the changes in plasma 3α,5α-THP as well as in GABAergic tonic currents and neuronal excitability caused by SI, but it had only a limited effect on the changes in the probability of presynaptic glutamate release. Overall, the results obtained in this work, together with those previously published, indicate that exposure of mice to SI during adolescence reduces neuronal excitability of DG granule cells, an effect that may be linked to the increased GABAergic tonic currents as a consequence of the sustained decrease in plasma and hippocampal levels of neurosteroids. All these changes may be consistent with cognitive deficits observed in animals exposed to such type of prolonged stress.

Sensorimotor gating deficits are inheritable in an isolation-rearing paradigm in rats

Early life experience is a key etiological factor of neuropsychiatric dysfunctions and is associated with developmental origins. Impaired prepulse inhibition (PPI) following an acoustic startle response is acknowledged as a cardinal characteristic in socially deprived weanling rats, which has been employed to investigate the underlying mechanisms of sensorimotor gating abnormalities in certain mental disorders, including schizophrenia. Because impaired PPI is a postnatal malfunction, it is interesting to examine whether it can be passed to the next generation. Isolation-rearing (IR) rats had been socially deprived since weaning, which mated with social rearing rats. Next, the offspring of IR rats were reared in a normal social environment. Locomotion, PPI, monoamines, and genes in schizophrenia-relevant brain areas [medial prefrontal cortex (mPFC) and hippocampus] were later measured. To this end, we observed that the next generation of IR offspring rats appeared with impaired PPI in which the PPI deficit can be observed as early as three weeks after birth. The third generation also exhibited lower levels of dopamine and serotonin in the mPFC and hippocampus; however, higher levels of both monoamines were measured in the striatum. Finally, Slc1a2 was more highly expressed in the mPFC of the third generation male rats. The present study demonstrates a transgenerational inheritance of IR-induced character and may help to elucidate the underlying pathoetiology of schizophrenia.

Disruptions of sensorimotor gating, cytokines, glycemia, monoamines, and genes in both sexes of rats reared in social isolation can be ameliorated by oral chronic quetiapine administration

The pathogenesis of schizophrenia in patients with metabolic abnormalities remains unclear. Our previous study demonstrated that isolation rearing (IR) induced longitudinal concomitant changes of pro-inflammatory cytokine (pro-CK) levels and metabolic abnormalities with a developmental origin. However, the general consensus, believes that these abnormalities are caused by antipsychotic treatment in schizophrenic patients. The IR paradigm presents with face, construct, and predictive validity for schizophrenia. Therefore, we employed IR rats of both sexes to examine whether chronic quetiapine (QTP, a second-generation antipsychotic medication) treatment induces disruptions of metabolism (body weight, blood pressure, and the glycemic and lipid profiles) or cytokines [interleukin (IL)-1 beta, IL-6, IL-10, interferon-gamma, and tumor necrosis factor (TNF)-alpha], and further, whether it reverses deficits of behaviors [locomotor activity and prepulse inhibition (PPI)] and the expression of monoamines (dopamine and serotonin) and related genes (Htr1a, Htr2a, Htr3a, Drd1a, and Gabbr2). IR induced higher levels of pro-CK, dysglycemia, blood pressure, locomotor activity, and impaired PPI, simultaneously destabilizing cortico-striatal monoamines and relevant genes in both sexes, while QTP demonstrated dose-dependent reversal of these changes, suggesting that QTP might reduce the pro-CKs to regulate these abnormalities. Our data implied that antipsychotics may not be the solitary factor causing metabolic problems in schizophrenia and suggested that inflammatory changes may play a vital role in the developmental pathophysiology of schizophrenia and related metabolic abnormalities.

Effects of SPAK knockout on sensorimotor gating, novelty exploration, and brain area-dependent expressions of NKCC1 and KCC2 in a mouse model of schizophrenia.

SPAK (Sterile 20/SPS1-related proline/alanine-rich kinase) is a protein kinase belonging to the mitogen-activated protein kinase (MAPK) superfamily that has been found to be extensively distributed across the body. The SPAK downstream substrates NKCC1 and KCC2 in the central nervous system are important in the interpretation of developmental mental disorders. The present study aimed to clarify the role of SPAK-NKCC1/KCC2 using a rodent schizophrenia-like model. The mouse paradigm of isolation rearing (IR) was employed, as it simulates the sensorimotor gating abnormalities of schizophrenia. SPAK transgenic mice were used and were divided into four groups: social-wild type, social-SPAK(-/-), isolation-wild type, and isolation-SPAK(-/-). The prepulse inhibition (PPI) test and the novel object recognition test (NORT) were used to measure schizophrenia-associated dysfunctions in gating ability and the novelty recognition, respectively. Finally, the protein expressions of NKCC1/KCC2 in the prefrontal cortex and hippocampus were detected to determine correlations with the behavioral data. Our results demonstrated that SPAK-null mice had superior PPI and novelty recognition relative to wild type controls, with a concomitant increase in KCC2 in the prefrontal cortex. IR disrupted PPI and NORT performances with an associated increase in KCC2. Furthermore, rearing environment and gene manipulation had mutually interactive effects, as the IR-induced effects on PPI and NORT were reversed by SPAK knockout, and the increase in KCC2 and the decreased in the NKCC1/KCC2 ratio in the prefrontal cortex induced by SPAK knockout were reversed by IR. Our data supported the gene-environment hypothesis and demonstrated the potential value of SPAK manipulation in future schizophrenia studies.

Citalopram attenuates tau hyperphosphorylation and spatial memory deficit induced by social isolation rearing in middle-aged rats.

Social isolation (SI) is considered as a chronic stress. Here, middle-aged rats (8 months) were group or isolation reared for 6 weeks. Following the initial two-week period of rearing, citalopram (10 mg/kg i.p.) was administered for 28 days. Changes in recognition memory, depression and anxiety-like behavior, and phosphorylated tau were investigated. We found that SI did not lead to obvious depression/anxiety-like behavior in middle-aged rats. Memory deficits and increased tau hyperphosphorylation at Tau-1, Ser396 episodes could be almost reversed by citalopram. The level of Ser9-phosphorylated GSK-3β (inactive form) was significantly decreased in the SI group which also could be almost reversed by citalopram, suggesting that the citalopram could prevent GSK-3β from SI-induced overactivation. The melatonin level was decreased in SI group compared with group housed (GH) group, and citalopram could partly restore the level of melatonin. We also found that citalopram could increase MT1 and MT2 in mRNA level. Our results demonstrate that citalopram increases the level of melatonin which negatively regulates GSK-3β and attenuates tau hyperphosphorylation and spatial memory deficit induced by SI in middle-aged rats. Suggesting that SI might constitute a risk factor for Alzheimer's disease (AD), and citalopram may represent a therapeutic strategy for the treatment of AD.

Social isolation rearing increases nucleus accumbens dopamine and norepinephrine responses to acute ethanol in adulthood.

Early-life stress is associated with increased vulnerability to alcohol addiction. However, the neural substrates linking chronic childhood/adolescent stress and increased risk of alcohol addiction are not well understood. In the nucleus accumbens (NAc), dopamine (DA) and norepinephrine (NE) signaling can be profoundly influenced by stress, anxiety, and drugs of abuse, including ethanol (EtOH). Here, we employed a rodent model of early-life stress that results in enduring increases in behavioral risk factors of alcoholism to gain a better understanding of how chronic adolescent stress may impact the EtOH sensitivity of DA and NE release in the NAc. Male Long-Evans rats were either group housed (GH; 4rats/cage) or socially isolated (SI; 1rat/cage) for 6weeks beginning on postnatal day 28. SI and GH rats were tested in adulthood for anxiety-like behaviors (elevated plus maze), and the effects of EtOH (1 and 2g/kg; intraperitoneally.) on NAc DA and NE were assessed by microdialysis. SI animals showed increased anxiety-like behavior compared to GH animals. Although SI had no effect on baseline levels of DA or NE, baseline DA levels were positively correlated with anxiety measures. In addition, while no significant differences were observed with 1g/kg EtOH, the 2g/kg dose induced significantly greater DA release in SI animals. Moreover, EtOH (2g/kg) only elevated NAc NE levels in SI rats. These results suggest that chronic early-life stress sensitizes accumbal DA and NE release in response to an acute EtOH challenge. A greater EtOH sensitivity of DA and NE release dynamics in the NAc may contribute to increases in behavioral risk factors of alcoholism, like greater EtOH self-administration, that are observed in SI rats.

Data calibration and reduction allows to visualize behavioural profiles of psychosocial influences in mice towards clinical domains

Psychosocial stress-particularly in combination with genetic vulnerability-is a critical environmental risk factor for psychiatric diseases in humans. Isolation rearing (IR) and social defeat (SD) paradigms model psychosocial risk factors in rodents, while enriched environment (EE) protects them from behavioural deficits. Studying the influence of various environmental conditions, e.g., on genetic mouse models can help to dissect the complex gene-environment relationships underlying human psychiatric diseases. Such studies may require analysing multiple mouse cohorts; however, the comparability of behavioural experiments is challenging and often compromised by practical limitations such as group sizes and influences of handling. Therefore, protocol standardization as well as appropriate statistical normalization is necessary to compare different experiments. In this study, we analysed two independent cohorts to compare the behavioural profiles of wild-type male mice subjected to IR and SD. In both cases, EE conditions served as a reference. Multivariate statistics was applied to merge the data from individual measures into broader categories (such as curiosity, anxiety and fear memory) by estimating their calibrated joint effect within a category. Plotting and overlaying these calibrated effect sizes in a single graph allowed intuitive comparison of IR and SD behavioural profiles. This approach allows analysing multiple behavioural tests at once, which is more relevant to psychiatric syndromes than focusing on single behavioural measures. Our method revealed that motivation and fear memory are impaired by both conditions, whereas ambulation and pain sensitivity are affected only by IR and curiosity is mainly diminished upon SD. Thus, IR could be a paradigm of choice in studies focusing on positive symptoms, while SD might be more relevant for negative and cognitive symptoms.