Water-finding Test Research Articles

Daily administration of yokukansan and keishito prevents social isolation-induced behavioral abnormalities and down-regulation of phosphorylation of neuroplasticity-related signaling molecules in mice

BackgroundOur previous studies demonstrated that post-weaning social isolation (ISO) in mice induces behavior abnormalities such as deficits of sociability- and attention-like behaviors. These deficits can be attenuated by methylphenidate (MPH), a drug used for attention deficit hyperactivity disorder (ADHD), suggesting that ISO mice offer a potential animal model of comorbid developmental disorder with ADHD and autism spectrum disorder symptoms. This study investigated the effects of Kampo formulae, yokukansan (YKS) and keishito (KST), on the neuropsychiatric symptoms of ISO mice to clarify the therapeutic or preventive/delaying potential of these formulae for the treatment of neurodevelopmental disorders.MethodsThree-to-4-week old male ICR mice were socially isolated during an experimental period and YKS and KST (1523.6 and 2031.8 mg/kg, p.o.) was administered starting from week 2 and week 0 after starting ISO for the analysis of their therapeutic and preventive/delaying potentials, respectively. Sociability, attention-related behavior and fear memory were elucidated by a 3 chamber test, a water-finding test and fear conditioning test, respectively. Moreover, the phosphorylation of neuroplasticity-related signaling molecules in mice hippocampus was analyzed using western blotting.ResultsIn a therapeutic procedure, YKS ameliorated ISO-induced impairments of attention-like behavior and context-dependent fear memory, but not of sociability, whereas KST had no beneficial effects in ISO mice. In experiments to analyze the preventive/delaying potentials of these treatments, both YKS and KST improved sociability, attention, and context-dependent fear memory deficits. The improvement of sociability in mice by YKS and KST was not inhibited by a dopamine D1 receptor antagonist, suggesting that YKS and KST improved the ISO-induced sociability deficit by other mechanisms besides activation of the dopaminergic system. On the other hand, the beneficial effects of YKS and KST on attention-like behavior were inhibited by a muscarinic antagonist, suggesting that YKS and KST ameliorated ISO-induced attention-like behavior through a cholinergic mechanism. Moreover, the phosphorylated forms of CaMKII and CREB were down-regulated by ISO stress and restored by YKS and KST administration.ConclusionsThese findings suggest that YKS and KST may be useful for the improvement of neurodevelopmental disorders.

Task-specific enhancement of hippocampus-dependent learning in mice deficient in monoacylglycerol lipase, the major hydrolyzing enzyme of the endocannabinoid 2-arachidonoylglycerol.

Growing evidence indicates that the endocannabinoid system is important for the acquisition and/or extinction of learning and memory. However, it is unclear which endocannabinoid(s) play(s) a crucial role in these cognitive functions, especially memory extinction. To elucidate the physiological role of 2-arachidonoylglycerol (2-AG), a major endocannabinoid, in behavioral and cognitive functions, we conducted a comprehensive behavioral test battery in knockout (KO) mice deficient in monoacylglycerol lipase (MGL), the major hydrolyzing enzyme of 2-AG. We found age-dependent increases in spontaneous physical activity (SPA) in MGL KO mice. Next, we tested the MGL KO mice using 5 hippocampus-dependent learning paradigms (i.e., Morris water maze (MWM), contextual fear conditioning, novel object recognition test, trace eyeblink conditioning, and water-finding test). In the MWM, MGL KO mice showed normal acquisition of reference memory, but exhibited significantly faster extinction of the learned behavior. Moreover, they showed faster memory acquisition on the reversal-learning task of the MWM. In contrast, in the contextual fear conditioning, MGL KO mice tended to show slower memory extinction. In the novel object recognition and water-finding tests, MGL KO mice exhibited enhanced memory acquisition. Trace eyeblink conditioning was not altered in MGL KO mice throughout the acquisition and extinction phases. These results indicate that 2-AG signaling is important for hippocampus-dependent learning and memory, but its contribution is highly task-dependent.

Prunella vulgaris Attenuates Prepulse Inhibition Deficit and Attention Disruption induced by MK‐801 in Mice

Prunella vulgaris var. lilacina is widely distributed in Korea, Japan, China, and Europe, and it has been traditionally used to treat inflammation or hypertension. In the present study, we investigated the effects of the ethanolic extract of the spikes of Prunella vulgaris var. lilacina (EEPV) on dizocilpine (MK-801)-induced schizophrenia-like phenotype behaviors such as the disruption of prepulse inhibition and attention deficits in mice. We also determined the effect of EEPV on MK-801-induced alterations in phosphorylated extracellular signal-regulated kinase, phosphorylated protein kinase B, phospho-glycogen synthase kinase 3-β, and phosphorylated cAMP response element-binding protein levels in the cortex and hippocampus of mice. MK-801-induced prepulse inhibition deficits were ameliorated by the administration of EEPV, as shown in the acoustic startle response test. Furthermore, EEPV attenuated the MK-801-induced attention deficits in the water finding test. We also found that EEPV attenuated the increased phosphorylated extracellular signal-regulated kinase, phosphorylated protein kinase B, or phospho-glycogen synthase kinase 3-β levels induced by MK-801 in the cortex but not in the hippocampus. These results suggest that EEPV could be useful for treating schizophrenia because EEPV ameliorates prepulse inhibition disruption and attention deficits induced by MK-801.

Early impairment in a water-finding test in a longitudinal study of the Tg2576 mouse model of Alzheimer's disease

Behavioral assessments of mouse models of neurodegenerative disorders are useful for investigating the molecular basis of the pathologies of the diseases. Here, we investigated the utility of a water-finding test using a video tracking system as a tool for evaluating cognitive deficits in Alzheimer's disease model mice. Transgenic mice expressing mutant amyloid precursor protein that incorporated the Swedish mutation (Tg2576 mice) were tested for behavioral alterations at 3, 5, 6, or 10 months of age. Tg2576 mice, which are widely used as a model of Alzheimer's disease, exhibited significant cognitive deficits in the water-finding test as early as 5 months of age. The impairments progressively worsened at 6 and 10 months of age. In addition, we analyzed spontaneous physical activities, such as locomotor activity, in the home-cage environment with an automated video analysis system (HomeCageScan). Our longitudinal study revealed that spontaneous behavior was altered in the Tg2576 mice, starting at the age of 10 months. Impairment in the Morris water maze (MWM) task was also first observed in the Tg2576 mice at the age of 10 months. These results indicated that the ability to perform the water-finding test was more susceptible to age-related cognitive deterioration in Tg2576 mice than the MWM test. We therefore propose that the water-finding test is a rapid and sensitive method that can be used to assess cognitive and/or behavioral deficits in mouse models of Alzheimer's disease.

Social isolation induces deficit of latent learning performance in mice: a putative animal model of attention deficit/hyperactivity disorder

Social isolation of rodents (SI) elicits a variety of stress responses such as increased aggressiveness, hyper-locomotion, and reduced susceptibility to pentobarbital. To obtain a better understanding of the relevance of SI-induced behavioral abnormalities to psychiatric disorders, we examined the effect of SI on latent learning as an index of spatial attention, and discussed the availability of SI as an epigenetic model of attention deficit hyperactivity disorder (ADHD). Except in specially stated cases, 4-week-old male mice were housed in a group or socially isolated for 3–70 days before experiments. The animals socially isolated for 1 week or more exhibited spatial attention deficit in the water-finding test. Re-socialized rearing for 5 weeks after 1-week SI failed to attenuate the spatial attention deficit. The effect of SI on spatial attention showed no gender difference or correlation with increased aggressive behavior. Moreover, SI had no effect on cognitive performance elucidated in a modified Y-maze or an object recognition test, but it significantly impaired contextual and conditional fear memory elucidated in the fear-conditioning test. Drugs used for ADHD therapy, methylphenidate (1–10mg/kg, i.p.) and caffeine (0.5–1mg/kg, i.p.), improved SI-induced latent learning deficit in a manner reversible with cholinergic but not dopaminergic antagonists. Considering the behavioral features of SI mice together with their susceptibility to ADHD drugs, the present findings suggest that SI provides an epigenetic animal model of ADHD and that central cholinergic systems play a role in the effect of methylphenidate on SI-induced spatial attention deficit.

Synergistic effect of combined treatment with risperidone and galantamine on phencyclidine-induced impairment of latent visuospatial learning and memory: Role of nAChR activation-dependent increase of dopamine D 1 receptor-mediated neurotransmission

The clinically achievable efficacy of the atypical antipsychotics on cognitive symptoms of schizophrenia is practically limited by their dose-dependent side effects. Thus, there is the need for adjuvant treatments or strategies for the cognitive impairments. Further, human autopsy and genetic data in schizophrenia have indicated the existence of the abnormality of nicotinic acetylcholine receptors (nAChR). In the present study, we aimed to investigate the synergistic effect and mechanisms of a combined treatment with an atypical antipsychotic risperidone and galantamine, which is a nAChR-allosteric modulator and a modest cholinesterase inhibitor, on the impairment of latent visuospatial learning and memory in mice resembling the cognitive impairment of schizophrenia. Repeated treatment with phencyclidine (PCP, 10 mg/kg, 14 days)-induced cognitive impairment in mice in a one trial water-finding test was used as a model of the cognitive impairment of schizophrenia. In vivo microdialysis was used to investigate the extracellular concentration of dopamine in the medial prefrontal cortex (mPFC). Combined treatment with galantamine and risperidone, at low, ineffective doses (both at 0.05 mg/kg) showed a synergistic effect to reverse cognitive impairment and increase extracellular concentration of dopamine in the mPFC. The synergistic behavioral effect was abolished by a dopamine-D 1 receptor antagonist, SCH 23390, and a nAChR antagonist, mecamylamine, but not a muscarinic AChR (mAChR) antagonist, scopolamine. Mecamylamine also blocked the synergistic effect on dopamine release in the mPFC of PCP-treated mice. The study indicates that galantamine and risperidone may have synergistic effect on the cognitive impairments in schizophrenia patients by synergistically promoting the nAChR activation-dependent increase of dopamine D 1 receptor-mediated neurotransmission.

Aqueous and hydroalcoholic extracts of Black Maca ( Lepidium meyenii) improve scopolamine-induced memory impairment in mice

Lepidium meyenii Walp. (Brassicaceae), known as Maca, is a Peruvian hypocotyl growing exclusively between 4000 and 4500 m altitude in the central Peruvian Andes, particularly in Junin plateau. Previously, Black variety of Maca showed to be more beneficial than other varieties of Maca on learning and memory in ovariectomized mice on the water finding test. The present study aimed to test two different doses of aqueous (0.50 and 2.00 g/kg) and hydroalcoholic (0.25 and 1.00 g/kg) extracts of Black Maca administered for 35 days on memory impairment induced by scopolamine (1 mg/kg body weight i.p.) in male mice. Memory and learning were evaluated using the water Morris maze and the step-down avoidance test. Brain acetylcholinesterase (AChE) and monoamine oxidase (MAO) activities in brain were also determined. Both extracts of Black Maca significantly ameliorated the scopolamine-induced memory impairment as measured in both the water Morris maze and the step-down avoidance tests. Black Maca extracts inhibited AChE activity, whereas MAO activity was not affected. These results indicate that Black Maca improves scopolamine-induced memory deficits.

Animal Model of Schizophrenia

In humans, phencyclidine (PCP), a noncompetitive N-methyl-d-aspartate (NMDA) antagonist, reproduces a schizophrenia-like psychosis such as positive/negative symptoms and cognitive deficits. PCP (10 mg/kg/day for 14 days)-treated mice exhibit the enhanced immobility in a forced swimming test as indexes of negative symptoms and impairment of latent learning in a water finding test as indexes of cognitive deficits. These behavioral deficits remain after withdrawal from repeated PCP treatment and are attenuated by atypical antipsychotics, but not by typical antipsychotics. Since it has been hypothesized that insufficient glutamate neurotransmission is involved in the pathophysiology of schizophrenia, we investigated an involvement of glutamatergic system in emotional and cognitive deficits in mice treated with PCP repeatedly. Ca(2+)/calmodulin kinase II (CaMKII) is markedly phosphorylated after the forced swimming test and the training trial of water finding test in the prefrontal cortex of saline-treated mice but not PCP-treated mice. Facilitation of NMDA receptor function by NMDA receptor glycine-site agonists such as D-cycloserine and glycine is effective on the abnormal intracellular signaling, and emotional and cognitive deficits in mice treated with PCP repeatedly. The repeated PCP treatment impaired NMDA receptor function and decreased levels of spontaneous extracellular glutamate in the prefrontal cortex, indicating that the repeated PCP treatment impairs both pre- and postsynaptic glutamate transmissions. Our findings suggest that abnormal NMDA receptor signaling is involved in the emotional and cognitive deficits in mice treated with PCP repeatedly. Our PCP-treated mice would be a useful model for studying the effect of antipsychotics on emotional and cognitive deficits in schizophrenia.

Characterization of learning and memory deficits in C57BL/6 mice infected with LP-BM5, a murine model of AIDS

Mice infected with an immunosuppressive murine leukemia virus mixture, LP-BM5 show a profound immunosuppression described as murine acquired immune deficiency syndrome (AIDS). In the present study, we characterized learning and memory deficits in C57BL/6 mice infected with LP-BM5. Spontaneous alternation behavior in a Y-maze and latent learning (spatial attention) in a water-finding test, as well as spatial reference and reversal learning in a water maze test, were significantly impaired in the mice infected with LP-BM5. These deficits appeared in the absence of any motoric and visual impairment as assessed by open-field, rotarod and visual water maze tests. These results suggest that cognitive functions are impaired in the mice infected with LP-BM5. Furthermore, LP-BM5-infected mice may be useful as a model for the AIDS dementia complex.

Enhancement of spatial attention in nociceptin/orphanin FQ receptor-knockout mice

We isolated genes for the opioid receptor homologue MOR-C, namely nociceptin receptor (designated alternatively as orphanin FQ receptor) and generated nociceptin receptor-knockout mice. Previously, we have reported that the nociceptin system appears to participate in the regulation of the auditory system. However, the behavior of the nociceptin receptor-knockout mice has yet to be fully characterized. In the present study, we investigated changes in several behavioral performances in mice which lack nociceptin receptor. Nociceptive thresholds of nociceptin receptor-knockout mice were unchanged in the hot-plate and electric foot-shock tests as well as tail-flick and acetic acid-induced writhing tests compared to those of wild-type mice. The nociceptin receptor-knockout mice did not show any behavioral changes in the elevated plus-maze task. Surprisingly, in the water-finding test, the nociceptin receptor-knockout mice showed an enhanced retention of spatial attention (latent learning) compared to wild-type mice. In a biochemical study, dopamine content in the frontal cortex was lower in nociceptin receptor-knockout mice than wild-type mice. These results suggest that nociceptin receptor plays an important role in spatial attention by regulating the dopaminergic system in the brain.

Prion protein is necessary for latent learning and long-term memory retention.

1. The cellular prion protein, designated PrPc, is a key molecule in the prion diseases but its physiological function remains unknown. To elucidate whether PrPc plays some role in the central nervous system, we established a line of mice in which the PrP gene had been disrupted and subsequently conducted long-term observations. 2. Performance in latent learning and passive avoidance was evaluated using water-finding and step-through tests, respectively. 3. PrP-/- mice showed impaired performance in the water-finding test, indicating a disturbance in latent learning, at 23 weeks of age. In the step-through test, although the PrP-/- mice showed normal learning ability and short-term memory retention, they evidenced a significant disturbance in long-term memory retention. 4. These results indicate that PrPc is needed for certain types of learning and memory and that the loss of function of this protein may contribute to the pathogenesis of prion diseases.

Effects of the subacute administration of nefiracetam on abnormal behavior in aged rats

We investigated the effects of nefiracetam on learning and memory by the Morris water maze task and water-finding test, and on emotional behavior by forced swimming, hole-board and open-field tests in old male Kbl Wistar rats aged 90 and 108 weeks. In the water maze task, the acquisition of the task in aged rats was slower than that in young rats. Subacute administration of nefiracetam (1 and 3 mg/kg daily) for 24 days tended to shorten the goal latency to escape onto the platform in a dose-dependent manner in the retention test, conducted 24 days after acquisition training. Nefiracetam (1 mg/kg) administration for 49 days decreased the duration of immobility in aged rats in the forced swimming test. Locomotor activity in young rats during the dark period was significantly higher than that during the light period, while there was no difference in Locomotor activity between the light and dark periods in aged rats, suggesting that Locomotor activity during the dark period and nocturnal habits may be impaired in aged rats. Subacute administration of nefiracetam for 14 days significantly increased the Locomotor activity during the dark, but not light, period in a dose-dependent manner. In addition, nefiracetam given for 38 days, significantly shortened the increased time elapsed before animals started exploring the environment in aged rats compared with young rats in the water-finding tests. These findings suggest that nefiracetam may improve the impaired nocturnal habits and some of emotional behavior in aged rats.

Effects of nefiracetam on drug-induced impairment of latent learning in mice in a water finding task

We investigated the effects of nefiracetam (DM-9384), a pyrrolidone derivative, on chlordiazepoxide-, apomorphine-, and methamphetamine-induced impairment of latent learning in a water finding test in mice. Pretreatment with nefiracetam reversed the inhibitory effects of chlordiazepoxide and apomorphine, but not those of methamphetamine, on latent learning. The ameliorative effects of nefiracetam on apomorphine-induced, but not chlordiazepoxide-induced impairment of latent learning were antagonized by scopolamine. These results provide further evidence that nefiracetam has anti-amnesic effects. Further, it is suggested that the cholinergic neuronal system may be involved in the ameliorative effects exerted by nefiracetam on apomorphine-induced impairment of latent learning.