d-Serine and a glycine transporter inhibitor improve MK-801-induced cognitive deficits in a novel object recognition test in rats

Vagus nerve stimulation (VNS) preventing postoperative cognitive dysfunction (POCD): two potential mechanisms in cognitive function

Postoperative cognitive dysfunction (POCD) impacts a significant number of patients annually, frequently impairing their cognitive abilities and resulting in unfavorable clinical outcomes. Aimed at addressing cognitive impairment, vagus nerve stimulation (VNS) is a therapeutic approach, which was used in many mental disordered diseases, through the modulation of vagus nerve activity. In POCD model, the enhancement of cognition function provided by VNS was shown, demonstrating VNS effect on cognition in POCD. In the present study, we primarily concentrates on elucidating the role of the VNS improving the cognitive function in POCD, via two potential mechanisms: the inflammatory microenvironment and epigenetics. This study provided a theoretical support for the feasibility that VNS can be a potential method to enhance cognition function in POCD.

Pretreatment with Liposome-Encapsulated Shrimp Shell Extract Attenuated Neuronal Damage and Death in Aβ1-42-Induced Memory Deficits in Rats

The accumulation of amyloid-beta (Aβ) peptides is a crucial factor in the neuronal degeneration of Alzheimer's disease (AD). The current study investigated the underlying neuroprotective mechanisms of shrimp shell extract (SSE) and liposome-encapsulated SSE (SSE/L) against Aβ1-42-induced neuronal damage and death in rats. Intracerebroventricular infusion of Aβ1-42 effectively induced memory decline, as observed in a reduction of the rat's discriminating ability in the novel object recognition and novel object location tasks. Oral pretreatment with 100 mg/kg of SSE demonstrated no preventive effect on the memory decline induced by Aβ1-42 infusion. However, treatment with SSE/L 100 mg/kg BW effectively attenuated memory deficits in both behavioral assessments following two and four weeks after Aβ1-42 infusion. Moreover, SSE/L exerted neuroprotective effects by reducing lipid peroxidation and increasing Nrf2/HO-1 expression. There was a significant decrease in Iba1 and GFAP (biomarkers of microglia and astrocyte activity, respectively), as well as a decrease in the levels of NF-κB expression and the inflammatory cytokines TNF-α and IL-6 in the cortical and hippocampal tissues. Treatment with SSE/L also reduced the pro-apoptotic proteins Bax and cleaved caspase-3 while raising the anti-apoptotic protein Bcl2. In addition, the beneficial effects of SSE/L were along with the effects of a positive control commercial astaxanthin (AST). The findings of this study indicated that SSE/L provided neuroprotective effects on Aβ1-42-induced AD rats by ameliorating oxidative stress, neuroinflammation and apoptotic cell death. Therefore, SSE/L might be employed to prevent and mitigate Aβ accumulation-induced neurotoxicity in AD.

NMDA Receptor Glycine Binding Site Modulators for Prevention and Treatment of Ketamine Use Disorder

Ketamine offers a fast-acting approach to relieving treatment-resistant depression, but its abuse potential is an issue of concern. As ketamine is a noncompetitive N-methyl-D-aspartate receptor (NMDAR) ion channel blocker, modulation of NMDAR might be an effective strategy to counteract the abuse liability of ketamine and even to treat ketamine use disorder. This study evaluated whether NMDAR modulators that act on glycine binding sites can decrease motivation to obtain ketamine and reduce reinstatement to ketamine-seeking behavior. Two NMDAR modulators, D-serine and sarcosine were examined. Male Sprague-Dawley rats underwent training to acquire the ability to self-administer ketamine. The motivation to self-administer ketamine or sucrose pellets was examined under a progressive ratio (PR) schedule. The reinstatement of ketamine-seeking and sucrose pellet-seeking behaviors were assessed after extinction. The results showed that both D-serine and sarcosine significantly decreased the breakpoints for ketamine and prevented reinstatement of ketamine seeking. However, these modulators did not alter motivated behavior for sucrose pellets, the ability of the cue and sucrose pellets to reinstate sucrose-seeking behavior or spontaneous locomotor activity. These findings indicate that two NMDAR modulators can specifically reduce the measures of motivation and relapse for ketamine in rats, suggesting that targeting the glycine binding site of the NMDAR is a promising approach for preventing and treating ketamine use disorder.

Vortioxetine improved negative and cognitive symptoms of schizophrenia in subchronic MK-801 model in rats

Schizophrenia is a devastating psychiatric disorder with complex symptoms and neurobiology. Serotonergic dysregulation is known to contribute to the pathogenesis of schizophrenia although dopaminergic and glutamatergic systems are thought to have central roles in neurobiology. No significant success can be achieved in the treatment of negative and cognitive symptoms while positive symptoms can be significantly reduced with current pharmacotherapy. Vortioxetine is a new multimodal antidepressant with 5-HT1A agonism, 5-HT1B partial agonism, 5-HT3, 5-HT7, and 5-HT1D antagonism, and serotonin reuptake inhibition. A limited number of studies suggest its therapeutic effect on the negative and cognitive symptoms of schizophrenia. Therefore, we investigated the potential beneficial effects of vortioxetine on behavioral and molecular deficits in the MK-801 model of schizophrenia in rats. Female Wistar albino rats (10-12 weeks) were grouped as saline, MK-801 (0.2 mg/kg), MK-801 + vortioxetine (2.5 mg/kg), MK-801 + vortioxetine (5 mg/kg), MK-801 + vortioxetine (10 mg/kg), MK-801 + risperidone (0.3 mg/kg), MK-801 + haloperidol (1 mg/kg) (n = 8 in each group). MK-801 has been daily administered (i.p.) for 14 days. Vortioxetine and antipsychotic treatments were injected for 21 days after a washout period of MK-801 and locomotor activity (LA), social interaction (SI), novel object recognition (NOR), Y-maze and prepulse inhibition (PPI) tests were performed at the 16-20th days of treatments, respectively. ELISA test was conducted to evaluate molecular analyses. MK-801 decreased PPI (%), social behaviors, and discrimination index in NOR and alternation (%) in the Y-maze test. In NOR and Y-maze tests, especially vortioxetine 5 and 10 mg/kg increased discrimination index and alternation (%) compared to MK-801. In addition, vortioxetine administration increased social behaviors. Moreover, MK-801 decreased GAD67 and parvalbumin levels while vortioxetine increased these protein levels compared to MK-801. Herein, we first suggested a potential therapeutic effect of vortioxetine, a new multimodal antidepressant, on negative and cognitive symptoms and neurobiological deficits including GAD67 and parvalbumin low expression in the MK-801 model in rats. It would be beneficial to confirm our results in different rodent models and to shed light on the possible mechanisms underlying these effects.

Functional crosstalk of the glycine transporter GlyT1 and NMDA receptors

NMDA-type glutamate receptors (NMDARs) constitute one of the main glutamate (Glu) targets in the central nervous system and are involved in synaptic plasticity, which is the molecular substrate of learning and memory. Hypofunction of NMDARs has been associated with schizophrenia, while overstimulation causes neuronal death in neurodegenerative diseases or in stroke. The function of NMDARs requires coincidental binding of Glu along with other cellular signals such as neuronal depolarization, and the presence of other endogenous ligands that modulate their activity by allosterism. Among these allosteric modulators are zinc, protons and Gly, which is an obligatory co-agonist. These characteristics differentiate NMDARs from other receptors, and their structural bases have begun to be established in recent years. In this review we focus on the crosstalk between Glu and glycine (Gly), whose concentration in the NMDAR microenvironment is maintained by various Gly transporters that remove or release it into the medium in a regulated manner. The GlyT1 transporter is particularly involved in this task, and has become a target of great interest for the treatment of schizophrenia since its inhibition leads to an increase in synaptic Gly levels that enhances the activity of NMDARs. However, the only drug that has completed phase III clinical trials did not yield the expected results. Notwithstanding, there are additional drugs that continue to be investigated, and it is hoped that knowledge gained from the recently published 3D structure of GlyT1 may allow the rational design of more effective new drugs.

Avocado peel extract: The effect of radiation-induced on neuroanatomical and behavioral changes in rats

Avocado (Persea americana) contains a variety of physiological active substances such as polyphenol, which has excellent antioxidant properties. This study investigated the radioprotective effect of avocado peel extract on congenital malformations and on the behavior of Sprague-Dawley (SD) rats. Experimental animals were randomly classified into four groups: NC Group, normal control; PA Group, oral administration with avocado peel extract (200 mg/kg/day); IR Group, irradiation; and PA+IR Group, irradiation after orally administered with avocado peel extract. For irradiation, 2 Gy of 6 MV X-ray was used once for the whole body. After that, congenital malformations, histopathological evaluation of the brain, and behavioral evaluation were performed in the obtained offspring. Although the body weight of the offspring was decreased by radiation exposure, it was confirmed that the decrease in weight was smaller when treated with PA. As the congenital malformations, hydrocephalus, loss of eyes, and abnormal rat tail occurred, and the result for the PA+IR Group was significantly lower than that of IR Group. Histopathologically, the length of the cerebral cortex of the PA+IR Group was similar to that of the non-radiation group. It was confirmed that emotional and behavioral disorders such as anxiety and depression were improved in the open field test (OFT) and elevated plus maze (EPM) test. And proved that working memory and cognitive ability were enhanced in the novel object recognition (NOR) test and spontaneous alternation Y-maze (SAY) test. Therefore, it was concluded that avocado peel extract can reduce the incidence of congenital malformations and improve growth disorders, memory and cognitive abilities. In the future, based on these results, we will conduct research on the hippocampus and amygdala, which are major regions of the brain, and additional research on cell biology.

Reduced attentional lapses in male rats following a combination treatment of low-dose D-serine and atomoxetine

BACKGROUND

Goal-directed attention involves the selective processing of behaviorally relevant sensory information. This selective processing is thought to be supported by glutamatergic and noradrenergic systems. Pharmacotherapies that simultaneously target these systems could therefore be effective treatments for impaired attention.

AIMS

We first tested an N-methyl-D-aspartate (NMDA) receptor co-agonist (D-serine) for effects on attention (processing speed and attentional lapses). NMDA receptor activation is thought to support noradrenergic effects on sensory processing; therefore, we tested a combination treatment comprising D-serine and a norepinephrine reuptake inhibitor (atomoxetine).

METHODS

D-serine was first tested in rats performing a two-choice visuospatial discrimination task. Combination treatments comprising relatively low doses of D-serine and atomoxetine were then tested in a separate group.

RESULTS

In experiment 1, D-serine reduced the skew of initiation time (IT) distributions (IT devmode) at the highest dose tested (300 mg/kg). In experiment 2, low-dose D-serine (125 mg/kg) had no effect, while low-dose atomoxetine (0.3 mg/kg) reduced IT devmode and slowed movement speed. Importantly, the combination of these relatively low doses of D-serine and atomoxetine reduced IT devmode more than either drug alone without further slowing movement speed.

CONCLUSIONS

IT devmode is thought to reflect attentional lapses; therefore, D-serine's effects on IT devmode suggest that NMDA receptors are involved in the preparatory deployment of attention. Greater effects following a combination of D-serine and atomoxetine suggest that preparatory attention can be facilitated by targeting glutamatergic and noradrenergic systems simultaneously. These results could inform the development of improved treatments for individuals with ADHD who experience abnormally high attentional lapses.

Maternal safflower oil consumption improve reflex maturation, memory and reduces hippocampal oxidative stress in the offspring rats treated during pregnancy and lactation

OBJECTIVE

Evaluate the influence of maternal consumption of safflower oil on reflex maturation, memory and offspring hippocampal oxidative stress.

METHODOLOGY

Two groups were formed: control group (C), whose mothers received a standard diet, and Safflower group (SF), whose mothers received a normolipidic diet with safflower oil as lipid source. Treatment was given from the 14th day of gestation and throughout lactation. To evaluate newborn development, the reflex ontogeny indicators between the 1st and the 21st days of life were evaluated; to assess memory, from the 42nd day of life on these animals were examined on open field habituation and novel object recognition test. Following behavioral analysis, the animals were anesthetized and decapitated. Hippocampus was rapidly dissected. In the hippocampal tissues, we evaluated the levels of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione S transferase (GST) and reduced glutathione (GSH).

RESULTS

SF offspring showed delayed maturation of reflexes and improvement of novel object recognition in short-term and long-term (p < 0.05). Safflower oil decreases lipid peroxidation evaluated by MDA levels (p < 0.001) and increases antioxidant defenses as shown by SOD, CAT, GST and GSH levels (p < 0.05). In our study, the composition of flavonoids present in the oil was not evaluated. Furthermore, in a future study, the effect of maternal consumption on female offspring should be verified.

CONCLUSION

Maternal intake of safflower oil could: (1) change neonate reflex parameters, (2) promote improvement of cognitive development in adolescence (3) improve antioxidant enzymatic and non-enzymatic defenses in the hippocampus.

Antipsychotic-like effects of fasudil, a Rho-kinase inhibitor, in a pharmacologic animal model of schizophrenia

Current antipsychotics used to treat schizophrenia have associated problems, including serious side effects and treatment resistance. We recently identified a significant association of schizophrenia with exonic copy number variations in the Rho GTPase activating protein 10 (ARHGAP10) gene using genome-wide analysis. ARHGAP10 encodes a RhoGAP superfamily member that is involved in small GTPase signaling. In mice, Arhgap10 gene variations result in RhoA/Rho-kinase pathway activation. We evaluated the pharmacokinetics of fasudil and hydroxyfasudil using liquid chromatography-tandem mass spectrometry in mice. The antipsychotic effects of fasudil on hyperlocomotion, social interaction deficits, prepulse inhibition deficits, and novel object recognition deficits were also investigated in a MK-801-treated pharmacological mouse schizophrenia model. Fasudil and its major metabolite, hydroxyfasudil, were detected in the brain at concentrations above their respective K_i values for Rho-kinase after intraperitoneal injection of 10 mg kg^-1 fasudil. Fasudil improved the hyperlocomotion, social interaction deficits, prepulse inhibition deficits, and novel object recognition deficits in MK-801-treated mice in a dose-dependent manner. Following oral administration of fasudil, brain hydroxyfasudil was detected at concentration above the K_i value for Rho-kinase whilst fasudil was undetectable. MK-801-induced hyperlocomotion was also improved by oral fasudil administration. These results suggest that fasudil has antipsychotic-like effects on the MK-801-treated pharmacological mouse schizophrenia model. There are two isoforms in Rho-kinase, and further investigation is needed to clarify the isoforms involved in the antipsychotic-like effects of fasudil in the MK-801-treated mouse schizophrenia model.

Hemodynamic changes and neuronal damage detected by 9.4 T MRI in rats with chronic cerebral ischemia and cognitive impairment

INTRODUCTION

The bilateral common carotid artery occlusion (BCCAO) rat model is an ideal animal model for simulating the pathology of chronic brain hypoperfusion in humans. However, dynamic changes in neuronal activity, cellular edema, and neuronal structural integrity in vivo after BCCAO have rarely been reported. The purpose of this study is to use a 9.4 T MRI to explore the pathophysiological mechanisms of vascular dementia.

MATERIALS AND METHODS

Twelve Sprague-Dawley (SD) rats were randomly divided into two groups: the sham group and the model group (n = 6 for each group). Rats were subjected to MRI using T2*WI, diffusion tensor imaging (DTI), and DWI sequences by MRI at the following six time points: presurgery and 6 h, 3 days, 7 days, 21 days, and 28 days postsurgery. Then, the T2*, fractional anisotropy (FA), and average apparent diffusion coefficient (ADC) values were measured in the bilateral cortices and hippocampi. After MRI scanning, all rats in both groups were subjected to the Y-maze test, novel object recognition test, and open-field test to assess their learning, memory, cognition, and locomotor activity.

RESULTS

The T2*, FA, and ADC values in the cerebral cortex and hippocampus decreased sharply at 6 h after BCCAO in the model group compared with those of the sham group. By Day 28, the T2* and ADC values gradually increased to close to those in the sham group, but the FA values changed little, and the rats in the model group had worse learning, memory, and cognition and less locomotor activity than the rats in the sham group.

CONCLUSIONS

The BCCAO is an ideal rat model for studying the pathophysiological mechanisms of vascular dementia.

Rational and Translational Implications of D-Amino Acids for Treatment-Resistant Schizophrenia: From Neurobiology to the Clinics

Schizophrenia has been conceptualized as a neurodevelopmental disorder with synaptic alterations and aberrant cortical–subcortical connections. Antipsychotics are the mainstay of schizophrenia treatment and nearly all share the common feature of dopamine D2 receptor occupancy, whereas glutamatergic abnormalities are not targeted by the presently available therapies. D-amino acids, acting as N-methyl-D-aspartate receptor (NMDAR) modulators, have emerged in the last few years as a potential augmentation strategy in those cases of schizophrenia that do not respond well to antipsychotics, a condition defined as treatment-resistant schizophrenia (TRS), affecting almost 30–40% of patients, and characterized by serious cognitive deficits and functional impairment. In the present systematic review, we address with a direct and reverse translational perspective the efficacy of D-amino acids, including D-serine, D-aspartate, and D-alanine, in poor responders. The impact of these molecules on the synaptic architecture is also considered in the light of dendritic spine changes reported in schizophrenia and antipsychotics’ effect on postsynaptic density proteins. Moreover, we describe compounds targeting D-amino acid oxidase and D-aspartate oxidase enzymes. Finally, other drugs acting at NMDAR and proxy of D-amino acids function, such as D-cycloserine, sarcosine, and glycine, are considered in the light of the clinical burden of TRS, together with other emerging molecules.

Behavioral Tagging: Role of Neurotransmitter Receptor Systems in Novel Object Recognition Long-Term Memory

Strong training is known to form long-term memory (LTM) as it is an inducer for both a learning tag (just like a synaptic tag/molecular tag) and plasticity-related proteins (PRPs), while weak training is an inducer of only a learning tag. However, weak training can also lead to LTM if paired with another behavioral task (open field in our study-a representative of a novel environment) around the time of PRP arrival. Weak behavioral training is a learning tag inducer, while the open field is a PRP inducer. The learning tag then captures these PRPs to form LTM. This is the basis of behavioral tagging (BT). BT is a well-known model for the evaluation of a few learning and memory forms. In this work, we examined the role of glutamate and D1/D5 (dopamine) receptors in the synthesis of a novel object recognition (NOR) tag (learning) as well as in PRP arrival, which come together to form NOR-LTM. Employing antagonists and/or agonists preceding or proceeding the open field and/or NOR training, it was revealed that the activation/stimulation of D1/D5 (dopamine) receptors and glutamatergic NMDA receptors plays a critical part in PRP arrival. We found that the activation/stimulation of NMDA receptors also contributes to the setting of the learning tag. Moreover, changes in glutamate, dopamine, and GABA neurotransmitter levels were also analyzed. These findings thus demonstrate the critical time window required for NOR-LTM formation based on the process of BT along with the role of activation/stimulation of D1/D5 (dopamine) receptors and NMDA receptors in the arrival of PRPs and learning tags for NOR-LTM formation.

Ginkgolide B inactivates the NLRP3 inflammasome by promoting autophagic degradation to improve learning and memory impairment in Alzheimer's disease

The NLR family, pyrin domain containing 3 (NLRP3) inflammasome drives the progression of Alzheimer's disease (AD). Ginkgolide B (GB) is a potential anti-inflammatory compound that controls neuro-inflammation. The aim of this study was to evaluate the effect of GB on the NLRP3 inflammasome in AD. The effect of GB on the conversion between the M1 and M2 microglial phenotype was examined using quantitative real-time PCR and immunostaining. Western blotting assays and ELISA were used to detect changes in neuro-inflammation following GB treatment, including the NLRP3 inflammasome pathway and autophagy. In order to evaluate the cognitive function of male senescence-accelerated mouse prone 8 (SAMP8) mice, behavioral tests, including the Morris water maze and novel object recognition tests, were performed. GB significantly decreased the intracellular pro-inflammatory cytokine levels in lipopolysaccharide-treated BV2 cells and improved cognitive behavior in SAMP8 mice. Moreover, GB deactivated the NLRP3 inflammasome, and this effect was dependent on autophagy. Ubiquitination was associated with GB-induced autophagic NLRP3 degradation. These results were further validated in the hippocampus of SAMP8 mice. Thus, GB exerted a neuroprotective effect on the cognitive function of SAMP8 mice by suppressing the activation of NLRP3 inflammasome via autophagic degradation.

Inhibition of Brain GTP Cyclohydrolase I Attenuates 3-Nitropropionic Acid-Induced Striatal Toxicity: Involvement of Mas Receptor/PI3k/Akt/CREB/ BDNF Axis

GTP cyclohydrolase I (GTPCH I) is the rate-limiting enzyme for tetrahydrobiopterin (BH4) biosynthesis; the latter is an essential factor for iNOS activation that contributes neuronal loss in Huntington’s disease (HD). The aim of the study was to investigate the neuroprotective effect of 2,4-diamino-6-hydroxypyrimidine (DAHP), GTPCH I enzyme inhibitor, against neuronal loss in 3-nitropropinic acid (3-NP)-induced HD in rats and to reveal the possible involved mechanisms mediated through PI3K/Akt axis and its correlation to Mas receptor (MasR). Rats received 3-NP (10 mg/kg/day; i.p.) with or without administration of DAHP (0.5 g/kg/day; i.p.) or wortmannin (WM), a PI3K inhibitor, (15 μg/kg/day; i.v.) for 14 days. DAHP improved cognitive, memory, and motor abnormalities induced by 3-NP, as confirmed by striatal histopathological specimens and immunohistochemical examination of GFAP. Moreover, DAHP treatment inhibited GTPCH I activity, resulting in decreased BH4 levels and iNOS activation. Also, DAHP upregulated the protein expression of survival protein; p85/p55 (pY458/199)-PI3K and pS473-Akt that, in turn, boosted the activation of striatal neurotrophic factors and receptor, pS133-CREB, BDNF and pY515-TrKB, which positively affect MasR protein expression and improve mitochondrial dysfunction, as indicated by enhancing both SDH and PGC-1α levels. Indeed, DAHP attenuates oxidative stress by increasing SOD activity and Nrf2 expression in addition to reducing neuro-inflammatory status by inhibiting NF-κB p65 and TNF-α expression. Interestingly, all the previous effects were blocked by co-administration of WM with DAHP. In conclusion, DAHP exerts neuroprotective effect against neuronal loss induced by 3-NP administration via inhibition of GTPCH I and iNOS activity and activation of MasR/PI3K/Akt/CREB/BDNF/TrKB axis besides its antioxidant and anti-inflammatory effect.

Linking proteomic alterations in schizophrenia hippocampus to NMDAr hypofunction in human neurons and oligodendrocytes

Glutamatergic neurotransmission dysfunction and the early involvement of the hippocampus have been proposed to be important aspects of the pathophysiology of schizophrenia. Here, we performed proteomic analysis of hippocampus postmortem samples from schizophrenia patients as well as neural cells-neurons and oligodendrocytes-treated with MK-801, an NMDA receptor antagonist. There were similarities in processes such as oxidative stress and apoptotic process when comparing hippocampus samples with MK-801-treated neurons, and in proteins synthesis when comparing hippocampus samples with MK-801-treated oligodendrocytes. This reveals that studying the effects of glutamatergic dysfunction in different neural cells can contribute to a better understanding of what it is observed in schizophrenia patients' postmortem brains.

Shenzhi Jiannao formula ameliorates vascular dementia in vivo and in vitro by inhibition glutamate neurotoxicity via promoting clathrin-mediated endocytosis

BACKGROUND

Synaptic damage and glutamate excitotoxicity have been implicated in the pathogenesis of vascular dementia (VD). Clathrin, RAB5B and N-methyl-D-aspartic acid receptor 1 (NMDAR1) proteins play a vital role in endocytosis of synaptic vesicles in neurons and glutamate over accumulation. Previous researches have been confirmed that Shenzhi Jiannao (SZJN) formula has an anti-apoptotic and neuroprotective effect in VD, but the underlying mechanisms are still unclear. In this study, we aimed to explore the effect of SZJN formula on cognitive impairment and glutamate excitotoxicity via clathrin-mediated endocytosis (CME) in vivo and in vitro.

METHODS

SZJN formula consists of Panax ginseng C.A.Mey., Anemarrhena asphodeloides Bunge, and Paeonia anomala subsp. veitchii (Lynch) D.Y.Hong & K.Y.Pan. All herbs were prepared into granules. Both common carotid arteries were permanent occluded (2-vessel occlusion, 2VO) in male Sprague Dawley (SD) rats to model VD. One day after operation, the rats began daily treatment with SZJN formula for 2 weeks. The neuroprotective effects of SZJN formula was subsequently assessed by the novel object recognition test, Morris water maze, hematoxylin-eosin (HE) staining and Nissl staining. Glutamate cytotoxicity was assessed by detecting cell viability and cell death of PC12 cells. Immunohistochemistry, immunofluorescence, Western blot, and quantitative real-time PCR were used to detect the expression levels of clathrin, RAB5B, and NMDAR1.

RESULTS

Administration of SZJN formula effectively improved short-term memory and spatial memory. SZJN formula treatment significantly reduced hippocampal neuronal loss, and recovered the arrangement and morphology of neurons and Nissl bodies. Moreover, SZJN formula promoted the proliferation of PC12 cells and inhibited glutamate-induced cell death. The down-regulation of clathrin and RAB5B, as well as the upregulation of NMDAR1 in the brain induced by 2VO or glutamate was also notably reversed by SZJN formula at both the protein and mRNA levels, which may contribute to SZJN formula induced improved neurological function.

CONCLUSIONS

Taken together, our findings provide evidence that the neuroprotective effects of SZJN formula in experimental VD maybe mediated through promoting the expression of clathrin-mediated endocytosis and reducing NMDARs-associated glutamate excitotoxicity. SZJN formula serves as a promising alternative therapy and may be a useful herbal medicine for preventing progression of VD.

Directly and Indirectly Targeting the Glycine Modulatory Site to Modulate NMDA Receptor Function to Address Unmet Medical Needs of Patients With Schizophrenia

Schizophrenia is a severe mental illness that affects ~1% of the world's population. It is clinically characterized by positive, negative, and cognitive symptoms. Currently available antipsychotic medications are relatively ineffective in improving negative and cognitive deficits, which are related to a patient's functional outcomes and quality of life. Negative symptoms and cognitive deficits are unmet by the antipsychotic medications developed to date. In recent decades, compelling animal and clinical studies have supported the NMDA receptor (NMDAR) hypofunction hypothesis of schizophrenia and have suggested some promising therapeutic agents. Notably, several NMDAR-enhancing agents, especially those that function through the glycine modulatory site (GMS) of NMDAR, cause significant reduction in psychotic and cognitive symptoms in patients with schizophrenia. Given that the NMDAR-mediated signaling pathway has been implicated in cognitive/social functions and that GMS is a potential therapeutic target for enhancing the activation of NMDARs, there is great interest in investigating the effects of direct and indirect GMS modulators and their therapeutic potential. In this review, we focus on describing preclinical and clinical studies of direct and indirect GMS modulators in the treatment of schizophrenia, including glycine, D-cycloserine, D-serine, glycine transporter 1 (GlyT1) inhibitors, and D-amino acid oxidase (DAO or DAAO) inhibitors. We highlight some of the most promising recently developed pharmacological compounds designed to either directly or indirectly target GMS and thus augment NMDAR function to treat the cognitive and negative symptoms of schizophrenia. Overall, the current findings suggest that indirectly targeting of GMS appears to be more beneficial and leads to less adverse effects than direct targeting of GMS to modulate NMDAR functions. Indirect GMS modulators, especially GlyT1 inhibitors and DAO inhibitors, open new avenues for the treatment of unmet medical needs for patients with schizophrenia.

Long Acting Polycaprolactone Based Parenteral Formulation of Aripiprazole Targeting Behavioural and Biochemical Deficit in Schizophrenia

Schizophrenia is a neurodevelopmental disorder which is expressed in the form of disturbed behaviour and abnormal mental functions. Patient's non-adherence to the medicine is the main cause of failure of drug therapy and increases incidence of relapses. Thus, for successful management of disease long acting parenteral formulations were developed. Aripiprazole was encapsulated in biocompatible polycaprolactone microsphere by o/w emulsion solvent-evaporation method in order to achieve sustained release of the drug for several weeks after single subcutaneous administration. They were optimised on the basis of various parameters such as physical appearance, particle size (49.4 μm-387.1 μm), encapsulation efficiency (70%-95%), percentage yield (33%-75%) and drug loading (25.9%-47.5%). The surface topography and sphericity of the microspheres was determined by scanning electron microscopy which revealed that the microspheres formed were spherical and non-porous in nature. The in vitro releases from the selected formulations were found to be 87% and 95% respectively after 45 days of dissolution. In vivo efficacy of optimised formulation showed significantly (p < 0.05) amelioration of various positive, negative and cognitive symptoms associated with schizophrenia and oxidative stress markers in ketamine-induced schizophrenia model in rats for 30 days.

Converging Evidence on D-Amino Acid Oxidase-Dependent Enhancement of Hippocampal Firing Activity and Passive Avoidance Learning in Rats

BACKGROUND

N-methyl-D-aspartate (NMDA) receptor activation requires the binding of a co-agonist on the glycine-binding site. D-serine is the main endogenous co-agonist of NMDA receptors, and its availability significantly depends on the activity of the metabolic enzyme D-amino acid oxidase (DAAO). Inhibition of DAAO increases the brain levels of D-serine and modulates a variety of physiological functions, including cognitive behavior.

METHODS

Here, we examined the effects of a novel 4-hydroxypyridazin-3(2H)-one derivative DAAO inhibitor, Compound 30 (CPD30), on passive avoidance learning and on neuronal firing activity in rats.

RESULTS

D-serine administration was applied as reference, which increased cognitive performance and enhanced hippocampal firing activity and responsiveness to NMDA after both local and systemic application. Similarly to D-serine, CPD30 (0.1 mg/kg) effectively reversed MK-801-induced memory impairment in the passive avoidance test. Furthermore, local iontophoretic application of CPD30 in the vicinity of hippocampal pyramidal neurons significantly increased firing rate and enhanced their responses to locally applied NMDA. CPD30 also enhanced hippocampal firing activity after systemic administration. In 0.1- to 1.0-mg/kg doses, CPD30 increased spontaneous and NMDA-evoked firing activity of the neurons. Effects of CPD30 on NMDA responsiveness emerged faster (at 10 minutes post-injection) when a 1.0-mg/kg dose was applied compared with the onset of the effects of 0.1 mg/kg CPD30 (at 30 minutes post-injection).

CONCLUSIONS

The present results confirm that the inhibition of DAAO enzyme is an effective strategy for cognitive enhancement. Our findings further facilitate the understanding of the cellular mechanisms underlying the behavioral effects of DAAO inhibition in the mammalian brain.

Phycocyanin alleviates ICV-STZ induced cognitive and molecular deficits via PI3-Kinase dependent pathway

In this study, the effect of Phycocyanin (Pc) to ameliorate the cognitive dysfunction in experimental model of Alzheimer's disease (AD) was evaluated. Intracerebroventricular (ICV) induction of Streptozotocin (STZ) (3 mg/kg) was done bilaterally twice in rats on alternative days. Rats were injected with Pc (50, 100 mg/kg; i. p.) for 28 days daily for behavioural and cholinergic activity assessment. As the effect was only significant at 100 mg/kg, later molecular experiments were performed using the same only. STZ induction led to increased activity of hippocampal cholinesterases and BAX and decreased activity of BCL-2 and ChAT. It enhanced TNF-α, and NF-κB in rat's brain and reduced BDNF and IGF-1 levels. Dysfunctional insulin signaling and decreased gene expressions of PI3-K, AKT was also observed. However, Pc treatment significantly prevented STZ-induced increased activity of hippocampal cholinesterases and BAX as well as increased the levels of BCL-2 and ChAT. Neuroinflammation was significantly attenuated and BDNF and IGF-1 levels were upregulated. Further, Pc also alleviated dysfunctional insulin signaling as evidenced by increased gene expression of IRS-1, PI3-K, AKT. In conclusion, our study demonstrated the immense potential of Pc in attenuating STZ-induced cognitive decline and it may be further explored as a therapeutic agent in managing AD.

Comparative Pro-cognitive and Neurochemical Profiles of Glycine Modulatory Site Agonists and Glycine Reuptake Inhibitors in the Rat: Potential Relevance to Cognitive Dysfunction and Its Management

Frontocortical NMDA receptors are pivotal in regulating cognition and mood, are hypofunctional in schizophrenia, and may contribute to autistic spectrum disorders. Despite extensive interest in agents potentiating activity at the co-agonist glycine modulatory site, few comparative functional studies exist. This study systematically compared the actions of the glycine reuptake inhibitors, sarcosine (40–200 mg/kg) and ORG24598 (0.63–5 mg/kg), the agonists, glycine (40–800 mg/kg), and D-serine (10–160 mg/kg) and the partial agonists, S18841 (2.5 mg/kg s.c.) and D-cycloserine (2.5–40 mg/kg) that all dose-dependently prevented scopolamine disruption of social recognition in adult rats. Over similar dose ranges, they also prevented a delay-induced impairment of novel object recognition (NOR). Glycine reuptake inhibitors specifically elevated glycine but not D-serine levels in rat prefrontal cortical (PFC) microdialysates, while glycine and D-serine markedly increased levels of glycine and D-serine, respectively. D-Cycloserine slightly elevated D-serine levels. Conversely, S18841 exerted no influence on glycine, D-serine, other amino acids, monamines, or acetylcholine. Reversal of NOR deficits by systemic S18841 was prevented by the NMDA receptor antagonist, CPP (20 mg/kg), and the glycine modulatory site antagonist, L701,324 (10 mg/kg). S18841 blocked deficits in NOR following microinjection into the PFC (2.5–10 μg/side) but not the striatum. Finally, in rats socially isolated from weaning (a neurodevelopmental model of schizophrenia), S18841 (2.5 and 10 mg/kg s.c.) reversed impairment of NOR and contextual fear-motivated learning without altering isolation-induced hyperactivity. In conclusion, despite contrasting neurochemical profiles, partial glycine site agonists and glycine reuptake inhibitors exhibit comparable pro-cognitive effects in rats of potential relevance to treatment of schizophrenia and other brain disorders where cognitive performance is impaired.

A Natural Product with High Affinity to Sigma and 5-HT7 Receptors as Novel Therapeutic Drug for Negative and Cognitive Symptoms of Schizophrenia

Dehydrocorybulbine (DHCB), an alkaloid from Corydalis yanhusuo. W.T, has been identified as a dopamine receptor antagonist. We extended our assessment of its pharmacological profile and found that DHCB exhibits high to moderate binding affinities to sigma 1 and 2 receptors, serotonin 5-HT7 receptor, and histamine H2 receptors. This led us to evaluate DHCB properties in pharmacological (apomorphine and MK-801) animal models of schizophrenia in mice. The pharmacological profile of DHCB was screened through radioligand receptor binding assays. Single dose of DHCB reversed the locomotor hyperactivity, stereotypy, and prepulse inhibition deficits induced by the dopaminergic agonist apomorphine. DHCB also reversed the depressive-like behavior and memory deficit induced by the glutamatergic antagonist MK-801 in the forced swim and the novel object recognition assays, respectively. These results indicate that DHCB effectively improves schizophrenia-like behavioral deficits that are induced by the disruption of dopaminergic and glutamatergic systems. The effectiveness of DHCB in reversing responses that mimic negative and cognitive deficits of schizophrenia might suggest that its anti-schizophrenia effects are mediated through modulating the activities of several receptor particularly sigma 1, sigma 2, 5-HT7 and dopamine receptors. Our study casts DHCB as a promising lead for therapeutic treatment of schizophrenia.

P11 Loss-of-Function is Associated with Decreased Cell Proliferation and Neurobehavioral Disorders in Mice

Although depression is associated with anxiety and memory deficit in humans, the molecular mechanisms of the complication remain largely unknown. In this study, we generated P11 knockout mice using CRISPR/Cas9 technology, as well as P11 knockout MEF cell lines, and confirmed depression-like phenotype. We observed that knockout of P11 in MEFs led to a decreased cell proliferation compared with P11+/+ MEFs. Moreover, P11 knockout resulted in a larger cell size, which resulted probably from accumulated F-actin stress fibers. The number of proliferating cells was decreased in the hippocampus of P11 KO mice. We observed anxiety-like disorder in addition to depression phenotype in the knockout mice. In addition, knockout of P11 led to memory deficit in female mice, but not in males. These data indicated that P11 is involved in regulating cell proliferation and cell size. The molecular associations of depression behavior with anxiety and memory deficit suggested a potential approach to improve therapeutic intervention through P11 in these disorders.

Short-Term Exposure to Enriched Environment in Adult Rats Restores MK-801-Induced Cognitive Deficits and GABAergic Interneuron Immunoreactivity Loss

Perinatal injections of N-methyl-D-aspartate (NMDA) receptor antagonist in rodents emulate some cognitive impairments and neurochemical alterations, such as decreased GABAergic (gamma aminobutyric acid) interneuron immunoreactivity, also found in schizophrenia. These features are pervasive, and developing neuroprotective or neurorestorative strategies is of special interest. In this work, we aimed to investigate if a short exposure to enriched environment (EE) in early adulthood (P55-P73) was an effective strategy to improve cognitive dysfunction and to restore interneuron expression in medial prefrontal cortex (mPFC) and hippocampus (HPC). For that purpose, we administered MK-801 intraperitoneally to Long Evans rats from postnatal days 10 to 20. Twenty-four hours after the last injection, MK-801 produced a transient decrease in spontaneous motor activity and exploration, but those abnormalities were absent at P24 and P55. The open field test on P73 manifested that EE reduced anxiety-like behavior. In addition, MK-801-treated rats showed cognitive impairment in novel object recognition test that was reversed by EE. We quantified different interneuron populations based on their calcium-binding protein expression (parvalbumin, calretinin, and calbindin), glutamic acid decarboxylase 67, and neuronal nuclei-positive cells by means of unbiased stereology and found that EE enhanced interneuron immunoreactivity up to normal values in MK-801-treated rats. Our results demonstrate that a timely intervention with EE is a powerful tool to reverse long-lasting changes in cognition and neurochemical markers of interneurons in an animal model of schizophrenia.

Cognition-Enhancing Vagus Nerve Stimulation Alters the Epigenetic Landscape

Vagus nerve stimulation (VNS) has been shown to enhance learning and memory, yet the mechanisms behind these enhancements are unknown. Here, we present evidence that epigenetic modulation underlies VNS-induced improvements in cognition. We show that VNS enhances novelty preference (NP); alters the hippocampal, cortical, and blood epigenetic transcriptomes; and epigenetically modulates neuronal plasticity and stress-response signaling genes in male Sprague Dawley rats. Brain-behavior analysis revealed structure-specific relationships between NP test performance (NPTP) and epigenetic alterations. In the hippocampus, NPTP correlated with decreased histone deacetylase 11 (HDAC11), a transcriptional repressor enriched in CA1 cells important for memory consolidation. In the cortex, the immediate early gene (IEG) ARC was increased in VNS rats and correlated with transcription of plasticity genes and epigenetic regulators, including HDAC3. For rats engaged in NPTP, ARC correlated with performance. Interestingly, blood ARC transcripts decreased in VNS rats performing NPTP, but increased in VNS-only rats. Because DNA double-strand breaks (DSBs) facilitate transcription of IEGs, we investigated phosphorylated H2A.X (γH2A.X), a histone modification known to colocalize with DSBs. In agreement with reduced cortical stress-response transcription factor NF-κB1, chromatin immunoprecipitation revealed reduced γH2A.X in the ARC promoter. Surprisingly, VNS did not significantly reduce transcription of cortical or hippocampal proinflammatory cytokines. However, TNFRSF11B (osteoprotegerin) correlated with NPTP as well as plasticity, stress-response signaling, and epigenetic regulation transcripts in both hippocampus and cortex. Together, our findings provide the first evidence that VNS induces widespread changes in the cognitive epigenetic landscape and specifically affects epigenetic modulators associated with NPTP, stress-response signaling, memory consolidation, and cortical neural remodeling.SIGNIFICANCE STATEMENT Recent studies have implicated vagus nerve stimulation (VNS) in enhanced learning and memory. However, whereas epigenetic modifications are known to play an important role in memory, the particular mechanisms involved in VNS-enhanced cognition are unknown. In this study, we examined brain and behavior changes in VNS and sham rats performing a multiday novelty preference (NP) task. We found that VNS activated specific histone modifications and DNA methylation changes at important stress-response signaling and plasticity genes. Both cortical and hippocampal plasticity changes were predictive of NP test performance. Our results reveal important epigenetic alterations associated with VNS cognitive improvements, as well as new potential pharmacological targets for enhancing cortical and hippocampal plasticity.

Effect of hydroalcoholic Echium amoenum extract on scopolamine-induced learning and memory impairment in rats

CONTEXT

Scopolamine, a muscarinic receptor antagonist, causes memory loss that resembles Alzheimer's disease (AD). Echium amoenum L. (Boraginaceae) is a famous medicinal plant of Iran that is traditionally used as a sedative and mood enhancer.

OBJECTIVE

This study evaluates the effect of hydroalcoholic extract of E. amoenum flowers on scopolamine-induced memory impairment in rats.

MATERIALS AND METHODS

Fifty male Wistar rats were randomly divided into five groups. Control group received normal saline, model group received scopolamine (0.7 mg/kg, IP, daily for 21 days), and test groups received E. amoenum extract (50, 75, and 100 mg/kg, IP, daily for 21 days) 30 min before each scopolamine injection. The elevated plus maze (EPM), shuttle box, novel object and rotarod tests were performed after treatment. Brain levels of malondialdehyde (MDA) and total antioxidant capacity (TCA) were also determined.

RESULTS

Scopolamine-treated rats spent more time exploring the novel object compared to the control, and E. amoenum extract at all three doses significantly decreased the time spent exploring the novel object (p < 0.05). E. amoenum extract (75 and 100 mg/kg) significantly elongated the secondary latency in rats receiving scopolamine in the shuttle box test (p < 0.05). In addition, treatment with 75 and 100 mg/kg doses of E. amoenum extract significantly ameliorated scopolamine-induced motor in coordination in rotarod test (p < 0.05). It also significantly increased the time spent in the open arms and reduced the time spent in the closed arms of EPM (p < 0.05). Treatment of scopolamine-exposed rats with E. amoenum extract significantly increased TCA and reduced MDA level of brain (p < 0.05).

DISCUSSION AND CONCLUSIONS

E. amoenum extract shows protective effect against scopolamine-induced impairment and is suggested to be tested in clinical trials to evaluate the efficacy on AD.

Glycine Transporters and Its Coupling with NMDA Receptors

Glycine plays two roles in neurotransmission. In caudal areas like the spinal cord and the brainstem, it acts as an inhibitory neurotransmitter, but in all regions of the CNS, it also works as a co-agonist with L-glutamate at N-methyl-D-aspartate receptors (NMDARs). The glycine fluxes in the CNS are regulated by two specific transporters for glycine, GlyT1 and GlyT2, perhaps with the cooperation of diverse neutral amino acid transporters like Asc-1 or SNAT5/SN2. While GlyT2 and Asc-1 are neuronal proteins, GlyT1 and SNAT5 are mainly astrocytic, although neuronal forms of GlyT1 also exist. GlyT1 has attracted considerable interest from the medical community and the pharmaceutical industry since compelling evidence indicates a clear association with the functioning of NMDARs, whose activity is decreased in various psychiatric illnesses. By controlling extracellular glycine, transporter inhibitors might potentiate the activity of NMDARs without activating excitotoxic processes. Physiologically, GlyT1 is a central actor in the cross talk between glutamatergic, glycinergic, dopaminergic, and probably other neurotransmitter systems. Many of these relationships begin to be unraveled by studies performed in recent years using genetic and pharmacological models. These studies are also clarifying the interactions between glycine, glycine transporters, and other co-agonists of the glycine site of NMDARs like D-serine. These findings are also relevant to understand the pathophysiology of devastating diseases like schizophrenia, depression, anxiety, epilepsy, stroke, and chronic pain.

Betulinic acid, a natural PDE inhibitor restores hippocampal cAMP/cGMP and BDNF, improve cerebral blood flow and recover memory deficits in permanent BCCAO induced vascular dementia in rats

Vascular dementia (VaD) is the second most common form of senile dementia, embraces memory deficits, neuroinflammation, executive function damage, mood and behavioral changes and abnormal cerebral blood flow. The purpose of the study was to explore the therapeutic potential of betulinic acid in bilateral common carotid artery occlusion (BCCAO) induced VaD in experimental rats. VaD was induced by BCCAO in rats and betulinic acid (10 and 15 mg/kg/day po) was administered 1 week after surgery. The cerebral blood pressure of the animal was recorded before and after the treatment using Laser Doppler flow meter. Object recognition task for non-spatial, Morris water maze for spatial and locomotor activity was performed to evaluate behavioral changes in rats. At the end of the study, animals were decapitated and hippocampus was separated to perform biochemical, neuroinflammatory and second messengers cAMP/cGMP analysis. Histology was done to study the brain pathophysiology. BCCAO surgery was able to significantly impaired memory in rats as observed behavioral and biochemical parameters. Moreover, BA demonstrated a neuroprotective effect in a dose-dependent manner. BA was able to re-establish cerebral blood flow, restore behavioral parameters and showed significant improvements in the as cAMP,cGMP and BDNF levels, restrain the oxidative stress and inflammatory parameters. In histopathology, betulinic acid treated groups showed a decrease in microgliosis and less pathological abnormalities comparable to diseased rat's brain. The observed effect might be attributed to the neuroprotective potential of betulinic acid and its ability to restore cognitive impairment and hippocampal neurochemistry in VaD.

Liraglutide prevents metabolic side-effects and improves recognition and working memory during antipsychotic treatment in rats

BACKGROUND

Antipsychotic drugs (APDs), olanzapine and clozapine, do not effectively address the cognitive symptoms of schizophrenia and can cause serious metabolic side-effects. Liraglutide is a synthetic glucagon-like peptide-1 (GLP-1) receptor agonist with anti-obesity and neuroprotective properties. The aim of this study was to examine whether liraglutide prevents weight gain/hyperglycaemia side-effects and cognitive deficits when co-administered from the commencement of olanzapine and clozapine treatment.

METHODS

Rats were administered olanzapine (2 mg/kg, three times daily (t.i.d.)), clozapine (12 mg/kg, t.i.d.), liraglutide (0.2 mg/kg, twice daily (b.i.d.)), olanzapine + liraglutide co-treatment, clozapine + liraglutide co-treatment or vehicle (Control) ( n = 12/group, 6 weeks). Recognition and working memory were examined using Novel Object Recognition (NOR) and T-Maze tests. Body weight, food intake, adiposity, locomotor activity and glucose tolerance were examined.

RESULTS

Liraglutide co-treatment prevented olanzapine- and clozapine-induced reductions in the NOR test discrimination ratio ( p < 0.001). Olanzapine, but not clozapine, reduced correct entries in the T-Maze test ( p < 0.05 versus Control) while liraglutide prevented this deficit. Liraglutide reduced olanzapine-induced weight gain and adiposity. Olanzapine significantly decreased voluntary locomotor activity and liraglutide co-treatment partially reversed this effect. Liraglutide improved clozapine-induced glucose intolerance.

CONCLUSION

Liraglutide co-treatment improved aspects of cognition, prevented obesity side-effects of olanzapine, and the hyperglycaemia caused by clozapine, when administered from the start of APD treatment. The results demonstrate a potential treatment for individuals at a high risk of experiencing adverse effects of APDs.

d-Serine administration affects nitric oxide synthase 1 adaptor protein and DISC1 expression in sex-specific manner

Antipsychotic medications are inefficient at treating symptoms of schizophrenia (SCZ), and N-methyl d-aspartate receptor (NMDAR) agonists are potential therapeutic alternatives. As such, these agonists may act on different pathways and proteins altered in the brains of patients with SCZ than do antipsychotic medications. Here, we investigate the effects of administration of the antipsychotic haloperidol and NMDAR agonist d-serine on function and expression of three proteins that play significant roles in SCZ: nitric oxide synthase 1 adaptor protein (NOS1AP), dopamine D2 (D2) receptor, and disrupted in schizophrenia 1 (DISC1). We administered haloperidol or d-serine to male and female Sprague Dawley rats via intraperitoneal injection for 12 days and subsequently examined cortical expression of NOS1AP, D2 receptor, and DISC1. We found sex-specific effects of haloperidol and d-serine treatment on the expression of these proteins. Haloperidol significantly reduced expression of D2 receptor in male, but not female, rats. Conversely, d-serine reduced expression of NOS1AP in male rats and did not affect D2 receptor expression. d-serine treatment also reduced expression of DISC1 in male rats and increased DISC1 expression in female rats. As NOS1AP is overexpressed in the cortex of patients with SCZ and negatively regulates NMDAR signaling, we subsequently examined whether treatment with antipsychotics or NMDAR agonists can reverse the detrimental effects of NOS1AP overexpression in vitro as previously reported by our group. NOS1AP overexpression promotes reduced dendrite branching in vitro, and as such, we treated cortical neurons overexpressing NOS1AP with different antipsychotics (haloperidol, clozapine, fluphenazine) or d-serine for 24 h and determined the effects of these drugs on NOS1AP expression and dendrite branching. While antipsychotics did not affect NOS1AP protein expression or dendrite branching in vitro, d-serine reduced NOS1AP expression and rescued NOS1AP-mediated reductions in dendrite branching. Taken together, our data suggest that d-serine influences the function and expression of NOS1AP, D2 receptor, and DISC1 in a sex-specific manner and reverses the effects of NOS1AP overexpression on dendrite morphology.

The Histamine H3 Receptor Antagonist DL77 Ameliorates MK801-Induced Memory Deficits in Rats

The role of Histamine H3 receptors (H3Rs) in memory, and the prospective of H3R antagonists in pharmacological control of neurodegenerative disorders, e.g., Alzheimer disease (AD) is well-accepted. For that reason, the procognitive effects of the H3R antagonist DL77 on cognitive impairments induced with MK801 were tested in an inhibitory passive avoidance paradigm (PAP) and novel object recognition (NOR) task in adult male rats, using donepezil (DOZ) as a standard drug. Acute systemic pretreatment with DL77 (2.5, 5, and 10 mg/kg, i.p.) significantly ameliorated memory deficits induced with MK801 in PAP (all P < 0.05, n = 7). The ameliorative effect of most promising dose of DL77 (5 mg/kg, i.p.) was reversed when rats were co-injected with the H3R agonist R-(α)-methylhistamine (RAMH, 10 mg/kg, i.p.) (p = 0.701 for MK801-amnesic group vs. MK801+DL77+RAMH group, n = 6). In the NOR paradigm, DL77 (5 mg/kg, i.p.) counteracted long-term memory (LTM) deficits induced with MK801 (P < 0.05, n = 6-8), and the DL77-provided effect was similar to that of DOZ (p = 0.788, n = 6-8), and was reversed when rats were co-injected with RAMH (10 mg/kg, i.p.) (p = 0.877, n = 6, as compared to the (MK801)-amnesic group). However, DL77 (5 mg/kg, i.p.) did not alter short-term memory (STM) impairment in NOR test (p = 0.772, n = 6-8, as compared to (MK801)-amnesic group). Moreover, DL77 (5 mg/kg) failed to modify anxiety and locomotor behaviors of animals innate to elevated-plus maze (EPM) (p = 0.67 for percentage of time spent exploring the open arms, p = 0.52 for number of entries into the open arms, p = 0.76 for percentage of entries into the open arms, and p = 0.73 number of closed arm entries as compared to saline-treated groups, all n = 6), demonstrating that the procognitive effects observed in PAP or NOR tests were unconnected to alterations in emotions or in natural locomotion of tested animals. These results signify the potential involvement of H3Rs in modulating neurotransmitters related to neurodegenerative disorders, e.g., AD.

Altered avalanche dynamics in a developmental NMDAR hypofunction model of cognitive impairment

Disturbed activity patterns in cortical networks contribute to the pathophysiology of schizophrenia (SZ). Several lines of evidence implicate NMDA receptor hypofunction in SZ, and blocking NMDA receptor signaling during early neurodevelopment produces cognitive deficits in rodent models that resemble those seen in schizophrenic patients. However, the altered network dynamics underlying these cognitive impairments largely remain to be characterized, especially at the cellular level. Here, we use in vivo two-photon calcium imaging to describe pathological dynamics, occurring in parallel with cognitive dysfunction, in a developmental NMDA receptor hypofunction model. We observed increased synchrony and specific alterations in spatiotemporal activity propagation, which could be causally linked to a previously unidentified persistent bursting phenotype. This phenotype was rescued by acute treatment with the NMDA receptor co-agonist D-serine or the GABA_B receptor agonist baclofen, which similarly rescued working memory performance. It was not reproduced by optogenetic inhibition of fast-spiking interneurons. These results provide novel insight into network-level abnormalities mediating the cognitive impairment induced by NMDA receptor hypofunction.

The Histamine H3 Receptor Antagonist E159 Reverses Memory Deficits Induced by Dizocilpine in Passive Avoidance and Novel Object Recognition Paradigm in Rats

The involvement of histamine H3 receptors (H3Rs) in memory is well known, and the potential of H3R antagonists in therapeutic management of neuropsychiatric diseases, e.g., Alzheimer disease (AD) is well established. Therefore, the effects of histamine H3 receptor (H3R) antagonist E159 (2.5–10 mg/kg, i.p.) in adult male rats on dizocilpine (DIZ)-induced memory deficits were studied in passive avoidance paradigm (PAP) and in novel object recognition (NOR) using pitolisant (PIT) and donepezil (DOZ) as standard drugs. Upon acute systemic pretreatment of E159 at three different doses, namely 2.5, 5, and 10 mg/kg, i.p., 2.5 and 5 but not 10 mg/kg of E159 counteracted the DIZ (0.1 mg)-induced memory deficits, and this E159 (2.5 mg)-elicited memory-improving effects in DIZ-induced amnesic model were moderately abrogated after acute systemic administration of scopolamine (SCO), H2R antagonist zolantidine (ZOL), but not with H1R antagonist pyrilamine to the animals. Moreover, the observed memory-enhancing effects of E159 (2.5 mg/kg, i.p.) were strongly abrogated when animals were administered with a combination of SCO and ZOL. Furthermore, the E159 (2.5 mg)-provided significant memory-improving effect of in DIZ-induced short-term memory (STM) impairment in NOR was comparable to the DOZ-provided memory-enhancing effect, and was abolished when animals were injected with the CNS-penetrant histamine H3R agonist R-(α)-methylhistamine (RAMH). However, E159 at a dose of 2.5 mg/kg failed to exhibit procognitive effect on DIZ-induced long-term memory (LTM) in NOR. Furthermore, the results observed revealed that E159 (2.5 mg/kg) did not alter anxiety levels and locomotor activity of animals naive to elevated-plus maze (EPM), demonstrating that improved performances with E159 (2.5 mg/kg) in PAP or NOR are unrelated to changes in emotional responding or in spontaneous locomotor activity. These results provide evidence for the potential of drugs targeting H3Rs for the treatment of neuropsychiatric disorders, e.g., AD.

Cannabinoids and Vanilloids in Schizophrenia: Neurophysiological Evidence and Directions for Basic Research

Much of our knowledge of the endocannabinoid system in schizophrenia comes from behavioral measures in rodents, like prepulse inhibition of the acoustic startle and open-field locomotion, which are commonly used along with neurochemical approaches or drug challenge designs. Such methods continue to map fundamental mechanisms of sensorimotor gating, hyperlocomotion, social interaction, and underlying monoaminergic, glutamatergic, and GABAergic disturbances. These strategies will require, however, a greater use of neurophysiological tools to better inform clinical research. In this sense, electrophysiology and viral vector-based circuit dissection, like optogenetics, can further elucidate how exogenous cannabinoids worsen (e.g., tetrahydrocannabinol, THC) or ameliorate (e.g., cannabidiol, CBD) schizophrenia symptoms, like hallucinations, delusions, and cognitive deficits. Also, recent studies point to a complex endocannabinoid-endovanilloid interplay, including the influence of anandamide (endogenous CB₁ and TRPV₁ agonist) on cognitive variables, such as aversive memory extinction. In fact, growing interest has been devoted to TRPV₁ receptors as promising therapeutic targets. Here, these issues are reviewed with an emphasis on the neurophysiological evidence. First, we contextualize imaging and electrographic findings in humans. Then, we present a comprehensive review on rodent electrophysiology. Finally, we discuss how basic research will benefit from further combining psychopharmacological and neurophysiological tools.

The antipsychotic-like effects in rodents of YQA31 involve dopamine D3 and 5-HT1A receptor

BACKGROUND

We previously reported that YQA31 is a dopamine D3 receptor antagonist with modest 5-HT1A receptor affinity and that it exhibits antipsychotic properties in animal models of schizophrenia. However, the contributions of D3 and 5-HT1A receptors in the anti-psychotic effects of YQA31 are not clear. The current study evaluated the role of these two receptors in the effect of YQA31 on the hyperactivity and novel object recognition deficit in mice.

METHODS

We used dopamine D3 receptor knockout mice and 5-HT1A receptor antagonist WAY100635 pretreatment, respectively, to investigate the involvement of these receptors in the effects of YQA31. The anti-psychotic effects were tested by inducing hyperlocomotion with methamphetamine or MK-801 and by inducing novel object recognition deficit with MK-801, which are the animal models to represent a positive symptom and a cognitive disorder.

RESULTS

YQA31 significantly inhibited MK-801-induced hyperlocomotion and novel object recognition deficit in WT mice, which was significantly inhibited by dopamine D3 receptor knockout. The 5-HT1A receptor antagonist, WAY100635, also blocked the effect of YQA31 in MK-801-induced novel object recognition deficit but not hyperlocomotion. The effect of YQA31 on methamphetamine-induced hyperlocomotion was not reversed by either dopamine D3 receptor knockout or WAY100635 pretreatment.

CONCLUSIONS

These results demonstrate the different roles of dopamine D3 and 5-HT1A receptors in the anti-psychotic effects of YQA31. Both dopamine D3 and 5-HT1A receptors contributed to the effects of YQA31 on the inhibition of MK-801-induced novel object recognition deficit, and the dopamine D3 receptor mediated the inhibiting effect of YQA31 on hyperlocomotion induced by MK-801.

Synaptic NMDA Receptor Activation Induces Ubiquitination and Degradation of STEP61

NMDA receptor signaling is critical for the development of synaptic plasticity, learning, and memory, and dysregulation of NMDAR signaling is implicated in a number of neurological disorders including schizophrenia (SZ). Previous work has demonstrated that the STriatal-Enriched protein tyrosine Phosphatase 61 kDa (STEP₆₁) is elevated in human SZ postmortem cortical samples and after administration of psychotomimetics to cultures or mice. Here, we report that activation of synaptic NMDAR by bicuculline or D-serine results in the ubiquitination and proteasomal degradation of STEP₆₁, and increased surface localization of GluN1/GluN2B receptors. Moreover, bicuculline or D-serine treatments rescue the motor and cognitive deficits in MK-801-treated mice and reduce STEP₆₁ in mouse frontal cortex. These results suggest that STEP₆₁ may contribute to the therapeutic effects of D-serine.

Pterostilbene ameliorates intracerebroventricular streptozotocin induced memory decline in rats

There is strong evidence that mitochondrial dysfunction mediated oxidative stress results in aging and energy metabolism deficits thus playing a prime role in pathogenesis of Alzheimer's disease, neuronal death and cognitive dysfunction. Evidences accrued in empirical studies suggest the antioxidant, anticancer and anti-inflammatory activities of the phytochemical pterostilbene (PTS). PTS also exhibits favourable pharmacokinetic attributes compared to other stilbenes. Hence, in the present study, we explored the neuroprotective role of PTS in ameliorating the intracerebroventricular administered streptozotocin (STZ) induced memory decline in rats. PTS at doses of 10, 30 and 50 mg/kg, was administered orally to STZ administered Sprague-Dawley (SD) rats. The learning and memory tests, Morris water maze test and novel object recognition test were performed which revealed improved cognition on PTS treatment. Further, there was an overall improvement in brain antioxidant parameters like elevated catalase and superoxide dismutase activities, GSH levels, lowered levels of nitrites, lipid peroxides and carbonylated proteins. There was improved cholinergic transmission as evident by decreased acetylcholinesterase activities. The action of ATPases (Na+ K+, Ca2+ and Mg2+) indicating the maintenance of cell membrane potential was also augmented. mRNA expression of battery of genes involved in cellular mitochondrial biogenesis and inflammation showed variations which extrapolate to hike in mitochondrial biogenesis and abated inflammation. The histological findings corroborated the effective role of PTS in countering STZ induced structural aberrations in brain.

N,N-dimethylglycine differentially modulates psychotomimetic and antidepressant-like effects of ketamine in mice

Ketamine, a dissociative anesthetic, produces rapid and sustained antidepressant effects at subanesthtic doses. However, it still inevitably induces psychotomimetic side effects. N,N-dimethylglycine (DMG) is a derivative of the amino acid glycine and is used as a dietary supplement. Recently, DMG has been found acting at glycine binding site of the N-methyl-d-aspartate receptor (NMDAR). As blockade of NMDARs is one of the main mechanisms responsible for the action of ketamine on central nervous system, DMG might modulate the behavioral responses to ketamine. The present study determined the effects of DMG on the ketamine-induced psychotomimetic, anesthetic and antidepressant-like effects in mice. DMG pretreatment reversed the ketamine-induced locomotor hyperactivity and impairment in the rotarod performance, novel location and novel object recognition tests, and prepulse inhibition. In addition, DMG alone exhibited antidepressant-like effects in the forced swim test and produced additive effects when combined with ketamine. However, DMG did not affect ketamine-induced anesthesia. These results reveal that DMG could antagonize ketamine's psychotomimetic effects, yet produce additive antidepressant-like effects with ketamine, suggesting that DMG might have antipsychotic potential and be suitable as an add-on therapy to ketamine for patients with treatment-resistant depression.

Time-dependent impact of glutamatergic modulators on the promnesiant effect of 5-HT6R blockade on mice recognition memory

Selective antagonists at serotonin 5-HT₆ receptors (5-HT₆R) improve memory performance in rodents and are currently under clinical investigations. If blockade of 5-HT₆R is known to increase glutamate release, only two studies have so far demonstrated an interaction between 5-HT₆R and glutamate transmission, but both, using the non-competitive NMDA antagonist MK-801, insensitive to variations of glutamate concentrations. In a place recognition task, we investigated here in mice the role of glutamate transmission in the beneficial effects of 5-HT₆R blockade (SB-271046). Through the use of increasing intervals (2, 4 and 6h) between acquisition and retrieval, we investigated the time-dependent impact of two different glutamatergic modulators. NMDAR-dependant glutamate transmission (NMDA Receptors) was either blocked by the competitive antagonist at NMDAR, CGS 19755, or potentiated by the glycine transporter type 1 (GlyT1) inhibitor, NFPS. Results showed that neither SB-271046, nor CGS 19755, nor NFPS, alter behavioural performances after short intervals, i.e. when control mice displayed significant memory performances (2h and 4h) (respectively 10, 3, and 0.625mg.kg^-1). Conversely, with the 6h-interval, a situation in which spontaneous forgetting is observed in control mice, SB-271046 improved recognition memory performances. This beneficial effect was prevented when co-administered with either CGS 19755 or NFPS, which themselves had no effect. Interestingly, a dose-dependent effect was observed with NFPS, with promnesic effect observed at lower dose (0.156mg.kg^-1) when administrated alone, whereas it did no modify promnesic effect of SB-271046. These results demonstrate that promnesiant effect induced by 5-HT₆R blockade is sensitive to the competitive blockade of NMDAR and underline the need of a fine adjustment of the inhibition of GlyT1. Overall, our findings support the idea of a complex crosstalk between serotonergic and glutamatergic systems in the promnesic properties of 5-HT₆R antagonists.

A novel Na(+) -Independent alanine-serine-cysteine transporter 1 inhibitor inhibits both influx and efflux of D-Serine

NMDA receptor dysfunctions are hypothesized to underlie the pathophysiology of schizophrenia, and treatment with D-serine (D-Ser), an NMDA receptor coagonist, may improve the clinical symptoms of schizophrenia. Thus, upregulating the synaptic D-Ser level is a novel strategy for schizophrenia treatment. Na(+) -independent alanine-serine-cysteine transporter 1 (asc-1) is a transporter responsible for regulating the extracellular D-Ser levels in the brain. In this study, we discovered a novel asc-1 inhibitor, (+)-amino(1-(3,5-dichlorophenyl)-3,5-dimethyl-1H-pyrazol-4-yl)acetic acid (ACPP), and assessed its pharmacological profile. ACPP inhibited the D-[(3) H]Ser uptake in human asc-1-expressing CHO cells and rat primary neurons with IC50 values of 0.72 ± 0.13 and 0.89 ± 0.30 μM, respectively. In accordance with the lower asc-1 expression levels in astrocytes, ACPP did not inhibit D-Ser uptake in rat primary astrocytes. In a microdialysis study, ACPP dose dependently decreased the extracellular D-Ser levels in the rat hippocampus under the same conditions in which the asc-1 inhibitor S-methyl-L-cysteine (SMLC) increased it. To obtain insights into this difference, we conducted a D-[(3) H]Ser efflux assay using asc-1-expressing CHO cells. ACPP inhibited D-[(3) H]Ser efflux, whereas SMLC increased it. These results suggest that ACPP is a novel inhibitor of asc-1. © 2016 Wiley Periodicals, Inc.

Modulation of glycine sites enhances social memory in rats using PQQ combined with d-serine

The aim of study was to investigate the effects of pyrroloquinoline quinone (PQQ) combined with d-serine on the modulation of glycine sites in the brain of rats using social recognition test. Rats were divided into seven groups (n=10) and given repeated intraperitoneal (ip) injections of saline, MK-801 (0.5mg/kg), clozapine (1mg/kg), haloperidol (0.1mg/kg), d-serine (0.8g/kg), PQQ (2.0μg/kg), or d-serine (0.4g/kg) combined with PQQ (1.0μg/kg) for seven days. A social recognition test, including assessment of time-dependent memory impairment, was performed. A non-competitive NMDA receptor antagonist, MK-801, significantly impaired social memory, and this impairment was significantly repaired with an atypical antipsychotic (clozapine) but not with a typical antipsychotic (haloperidol). Likewise, d-serine combined with PQQ significantly improved MK-801-disrupted cognition in naïve rats, whereas haloperidol was ineffective. The present results show that the co-agonist NMDA receptor treated with PQQ and d-serine enhances social memory and may be an effective approach for treating the cognitive dysfunction observed in schizophrenic patients. PQQ stimulates glycine modulatory sites by which it may antagonize indirectly by removing glycine from the synaptic cleft or by binding the unsaturated site with d-serine in the brain, providing the insights into future research of central nervous system and drug discovery.