PWZ-029, an inverse agonist selective for α₅ GABAA receptors, improves object recognition, but not water-maze memory in normal and scopolamine-treated rats

Diet enriched with high-phenolic cocoa potentiates hippocampal brain-derived neurotrophic factor expression and neurogenesis in healthy adult micewith subtle effects on memory

Cocoa is widely known for its health benefits, but its neurocognitive impact remains underexplored. This preclinical study aimed to investigate the effects of cocoa and cocoa polyphenols on hippocampal neuroplasticity, cognitive function and emotional behavior. Seventy young-adult C57BL/6JRj male and female mice were fed either a standard diet (CTR) or a diet enriched with 10% high-phenolic content cocoa (HPC) or low-phenolic content cocoa (LPC) for at least four weeks. In a first experiment, behavioral tests assessing exploratory behavior, emotional responses and hippocampal-dependent memory were conducted four weeks into the diet, followed by animal sacrifice a week later. Adult hippocampal neurogenesis and brain-derived neurotrophic factor (BDNF) expression in the hippocampus and prefrontal cortex were evaluated using immunohistochemistry and western blot. In a different experiment, hippocampal synaptic response, long-term potentiation and presynaptic-dependent short-term plasticity were studied by electrophysiology. Cocoa-enriched diets had minimal effects on exploratory activity and anxiety-like behavior, except for reduced locomotion in the LPC group. Only the HPC diet enhanced object recognition memory, while place recognition memory and spatial navigation remained unaffected. The HPC diet also increased adult hippocampal neurogenesis, boosting the proliferation, survival and number of young adult-born neurons. However, both cocoa-enriched diets increased immobility in the forced swimming test and hippocampal BDNF expression. Hippocampal electrophysiology revealed no alterations in neuroplasticity among diets. The results were mostly unaffected by sex. Overall, the HPC diet demonstrated greater potential regarding cognitive and neuroplastic benefits, suggesting a key role of cocoa flavanols in dietary interventions aimed at enhancing brain health.

The antidepressant drugs vortioxetine and duloxetine differentially and sex-dependently affect animal well-being, cognitive performance, cardiac redox status and histology in a model of osteoarthritis

Osteoarthritis represents a leading cause of disability with limited treatment options. Furthermore, it is frequently accompanied by cardiovascular and cognitive disorders, which can be exacerbated by osteoarthritis or drugs used for its treatment. Here, we examined the behavioral and cardiac effects of the novel antidepressant vortioxetine in an osteoarthritis model, and compared them to duloxetine (an established osteoarthritis treatment). Osteoarthritis was induced in male and female rats with an intraarticular sodium-monoiodoacetate injection. Antidepressants were orally administered for 28 days following induction. During this period the acetone, burrowing and novel-object-recognition tests (NORT) were used to assess the effects of antidepressants on pain hypersensitivity (cold allodynia), animal well-being and cognitive performance, respectively. Following behavioral experiments, heart muscles were collected for assessment of redox status/histology. Antidepressant treatment dose-dependently reduced cold allodynia in rats with osteoarthritis. Duloxetine (but not vortioxetine) depressed burrowing behavior in osteoarthritic rats in a dose-related manner. Osteoarthritis induction reduced cognitive performance in NORT, which was dose-dependently alleviated by vortioxetine (duloxetine improved performance only in female rats). Furthermore, duloxetine (but not vortioxetine) increased oxidative stress parameters in the heart muscles of female (but not male) rats and induced histological changes in cardiomyocytes indicative of oxidative damage. Vortioxetine displayed comparable efficacy to duloxetine in reducing pain hypersensitivity. Furthermore, vortioxetine (unlike duloxetine) dose-dependently improved cognitive performance and had no adverse effect on burrowing behavior (animal surrogate of well-being) and cardiac redox status/histology. Our results indicate that vortioxetine could be a potential osteoarthritis treatment (with better characteristics compared to duloxetine).

Effects of α5 GABAA receptor modulation on social interaction, memory, and neuroinflammation in a mouse model of Alzheimer's disease

AIMS

GABAergic modulation involved in cognitive processing appears to be substantially changed in Alzheimer's disease (AD). In a widely used 5xFAD model of AD, we aimed to assess if negative and positive allosteric modulators of α5 GABAA receptors (NAM and PAM, respectively) would affect social interaction, social, object and spatial memory, and neuroinflammation.

METHODS

After 10-day treatment with PAM, NAM, or solvent, 6-month-old transgenic and non-transgenic 5xFAD mice underwent testing in a behavioral battery. Gene expressions of IL-1β, IL-6, TNF-α, GFAP, and IBA-1 were determined in hippocampus and prefrontal cortex by qPCR.

RESULTS

PAM treatment impaired spatial learning in transgenic females compared to solvent-treated transgenic females, and social recognition in transgenic and non-transgenic males. NAM treatment declined social interaction in transgenic and non-transgenic males, while had beneficial effect on cognitive flexibility in non-transgenic males compared to solvent-treated non-transgenic males. Transgenic animals have not fully displayed cognitive symptoms, but neuroinflammation was confirmed. NAM reduced proinflammatory gene expressions in transgenic females and astrogliosis in transgenic males compared to pathological controls.

CONCLUSION

PAM and NAM failed to exert favorable behavioral effects in transgenic animals. Suppression of neuroinflammation obtained with NAM calls for more studies with GABAergic ligands in amyloid beta- and/or tau-dependent models with prominent neuroinflammation.

The Case for Clinical Trials with Novel GABAergic Drugs in Diabetes Mellitus and Obesity

Obesity and diabetes mellitus have become the surprising menaces of relative economic well-being worldwide. Gamma amino butyric acid (GABA) has a prominent role in the control of blood glucose, energy homeostasis as well as food intake at several levels of regulation. The effects of GABA in the body are exerted through ionotropic GABAA and metabotropic GABAB receptors. This treatise will focus on the pharmacologic targeting of GABAA receptors to reap beneficial therapeutic effects in diabetes mellitus and obesity. A new crop of drugs selectively targeting GABAA receptors has been under investigation for efficacy in stroke recovery and cognitive deficits associated with schizophrenia. Although these trials have produced mixed outcomes the compounds are safe to use in humans. Preclinical evidence is summarized here to support the rationale of testing some of these compounds in diabetic patients receiving insulin in order to achieve better control of blood glucose levels and to combat the decline of cognitive performance. Potential therapeutic benefits could be achieved (i) By resetting the hypoglycemic counter-regulatory response; (ii) Through trophic actions on pancreatic islets, (iii) By the mobilization of antioxidant defence mechanisms in the brain. Furthermore, preclinical proof-of-concept work, as well as clinical trials that apply the novel GABAA compounds in eating disorders, e.g., olanzapine-induced weight-gain, also appear warranted.

Positive modulation of α5GABAA receptors leads to dichotomous effects in rats on memory pattern and GABRA5 expression in prefrontal cortex and hippocampus

Positive allosteric modulators (PAMs) of α5GABA_A receptors (α5GABAARs) are emerging as potential therapeutics for a range of neuropsychiatric disorders. However, their role in memory processing of healthy animals is not sufficiently examined. We tested the effects of MP-III-022 (1 mg/kg, 2.5 mg/kg and 10 mg/kg), a PAM known to be selective for α5GABAARs and devoid of prominent side-effects, in different behavioral paradigms (Morris water maze, novel object recognition test and social novelty discrimination) and on GABRA5 expression in Wistar rats, 30 min and 24 h after intraperitoneal treatment administration. The lowest dose tested worsened short-term object memory. The same dose, administered two times in a span of 24 h, improved spatial and impaired object and, at a trend level, social memory. The highest dose had a detrimental effect on all types of long-term memory (object memory at a trend level) and short-term spatial memory, but improved short-term object and social memory. Distinct sets of expression changes were detected in both prefrontal cortex and two regions of the hippocampus, but the latter ones could be assessed as more consequential. An increase of GABRA5 mRNA in CA2 occurred in parallel with improvement of object and social, but impairment of spatial memory, while the opposite happened with a trend level change in CA1. Our study demonstrates the variability of the roles of the α5GABAAR based on its level of expression and localization, in dependence on the type and protocol of cognitive tasks, as well as the respective timing of pharmacological modulation and testing.

A multi-dosing regimen to enhance the spatial memory of normal rats with α5-containing GABAA receptor negative allosteric modulator L-655,708

RATIONALE AND OBJECTIVES

The reported inconsistent effects of negative allosteric modulators of α5-containing GABA_A receptors on learning and memory may be attributed to receptor selectivity, effective plasma concentration maintenance, and administration time. This study aimed to compare the effects of L-655,708 administered by single-dosing regimen versus multi-dosing regimen on spatial memory, signaling molecules, and brain functional connectivity.

METHODS

After comparing the maintenance time of the effective plasma concentration of L-655,708 between multi-dosing and single-dosing regimens, we further compared the effects of the administration of the two regimens at different phases (before-learning, during-learning, and before-probe) of the Morris water maze (MWM) test on the performance of learning and memory and the levels of signaling molecules related to learning and memory in hippocampal tissues. Functional connectivity analyses between hippocampal and cortical regions were performed to further clarify the effects of the multi-dosing regimen.

RESULTS

The multi-dosing regimen could maintain the effective plasma concentration of L-655,708 much longer than the single-dosing regimen. Only the multi-dosing regimen for L-655,708 administration during the learning period led to significant improvement in spatial memory in the MWM test and increases in levels of glutamate receptors and phosphorylated signaling molecules (p-PKAα, p-CaMKII, and p-CREB-1). Compared with the vehicle control, the multi-dosing regimen increased the functional connectivity of the left hippocampal CA1 with cingulate and motor cortices.

CONCLUSIONS

A multi-dosing regimen for L-655,708 administered during the learning period is an effective strategy to improve spatial memory, increase signaling molecule levels, and enhance the functional connectivity of the hippocampus.

JM-20 treatment prevents neuronal damage and memory impairment induced by aluminum chloride in rats

The number of people with dementia worldwide is estimated at 50 million by 2018 and continues to rise mainly due to increasing aging and population growth. Clinical impact of current interventions remains modest and all efforts aimed at the identification of new therapeutic approaches are therefore critical. Previously, we showed that JM-20, a dihydropyridine-benzodiazepine hybrid molecule, protected memory processes against scopolamine-induced cholinergic dysfunction. In order to gain further insight into the therapeutic potential of JM-20 on cognitive decline and Alzheimer's disease (AD) pathology, here we evaluated its neuroprotective effects after chronic aluminum chloride (AlCl3) administration to rats and assessed possible alterations in several types of episodic memory and associated pathological mechanisms. Oral administration of aluminum to rodents recapitulates several neuropathological alterations and cognitive impairment, being considered a convenient tool for testing the efficacy of new therapies for dementia. We used behavioral tasks to test spatial, emotional- associative and novel object recognition memory, as well as molecular, enzymatic and histological assays to evaluate selected biochemical parameters. Our study revealed that JM-20 prevented memory decline alongside the inhibition of AlCl3 -induced oxidative stress, increased AChE activity, TNF-α and pro-apoptotic proteins (like Bax, caspase-3, and 8) levels. JM-20 also protected against neuronal damage in the hippocampus and prefrontal cortex. Our findings expanded our understanding of the ability of JM-20 to preserve memory in rats under neurotoxic conditions and confirm its potential capacity to counteract cognitive impairment and etiological factors of AD by breaking the progression of key steps associated with neurodegeneration.

Increased expression of GABAA receptor subunits associated with tonic inhibition in patients with temporal lobe epilepsy

Epilepsy animal models indicate pronounced changes in the expression and rearrangement of GABA_A receptor subunits in the hippocampus and in para-hippocampal areas, including widespread downregulation of the subunits α5 and δ, and upregulation of α4, subunits that mediate tonic inhibition of GABA. In this case–control study, we investigated changes in the expression of subunits α4, α5 and δ in hippocampal specimens of drug resistant temporal lobe epilepsy patients who underwent epilepsy surgery. Using in situ hybridization, immunohistochemistry and α5-specific receptor autoradiography, we characterized expression of the receptor subunits in specimens from patients with and without Ammon’s horn sclerosis compared to post-mortem controls. Expression of the α5-subunit was abundant throughout all subfields of the hippocampus, including the dentate gyrus, sectors CA1 and CA3, the subiculum and pre- and parasubiculum. Significant but weaker expression was detected for subunits α4 and δ notably in the granule cell/molecular layer of control specimens, but was faint in the other parts of the hippocampus. Expression of all three subunits was similarly altered in sclerotic and non-sclerotic specimens. Respective mRNA levels were increased by about 50–80% in the granule cell layer compared with post-mortem controls. Subunit α5 mRNA levels and immunoreactivities were also increased in the sector CA3 and in the subiculum. Autoradiography for α5-containing receptors using [³H]L-655,708 as ligand showed significantly increased binding in the molecular layer of the dentate gyrus in non-sclerotic specimens. Increased expression of the α5 and δ subunits is in contrast to the previously observed downregulation of these subunits in different epilepsy models, whereas increased expression of α4 in temporal lobe epilepsy patients is consistent with that in the rodent models. Our findings indicate increased tonic inhibition likely representing an endogenous anticonvulsive mechanism in temporal lobe epilepsy.

Positive and Negative Selective Allosteric Modulators of α5 GABAA Receptors: Effects on Emotionality, Motivation, and Motor Function in the 5xFAD Model of Alzheimer's Disease

BACKGROUND

Positive and negative allosteric modulators of α5 GABAA receptors (PAM and NAM, respectively) are worthy of investigation as putative treatments of Alzheimer's disease (AD). However, their potential to modify a dynamic range of behaviors in AD models needs to be systematically examined.

OBJECTIVE

The study aimed to assess effects of MP-III-022 as PAM and PWZ-029 as NAM on emotional reactivity, motivation, and motor function, as well as on gene expression of GABRA2, GABRA3 and GABRA5 subunit of GABAA receptors in prefrontal cortex (PFC) and hippocampus (HC) in 5xFAD mice, as an early-onset transgenic AD model.

METHODS

The 6-month-old 5xFAD transgenic and non-transgenic mice of both genders underwent a battery of reflexes and behavioral tests (sensorimotor tests, elevated plus maze, and open field) after 10-day intraperitoneal treatment with MP-III-022, PWZ-029, or solvent. The behavioral battery was followed by qPCR analysis of gene expression.

RESULTS

MP-III-022 induced a decline in motor function, while PWZ-029 further decreased emotionality of transgenic males, as compared to the transgenic control. No interfering effects on non-cognitive behavior were observed in female mice. In HC, both treatments reversed reciprocal GABRA2 and GABRA3 changes in transgenic females. In PFC, MP-III-022 decreased GABRA5 in both genders, while PWZ-029 increased GABRA2 in male transgenic animals.

CONCLUSION

Gender-dependent protracted effects of PAMs and NAMs in AD model, with detrimental impact on motor capabilities of PAM, and attenuation of emotionality elicited by NAM in transgenic males, were revealed. This favors future research of α5 GABAA receptor modulation in females as more promising.

Altered GABA-mediated information processing and cognitive dysfunctions in depression and other brain disorders

Cognitive dysfunctions, including impaired attention, learning, memory, planning and problem solving, occur in depressive episodes, often persist during remission, predict relapse, worsen with recurrent episodes, and are not treated by current antidepressants or other medications. Cognitive symptoms are also present in other psychiatric disorders, are a hallmark of aging, and define several late-life disorders, including Alzheimer's disease. This pervasive occurrence suggests either a non-specific outcome of a diseased brain, or a shared underlying pathology contributing to this symptom dimension. Recent findings suggest a role for altered GABAergic inhibition in cognitive symptoms. Cellular, molecular and biochemical studies in human subjects report changes affecting the gamma-amino butyric acid (GABA) system, specifically somatostatin-expressing (SST+) GABAergic interneurons, across brain disorders and during aging. SST+ neurons gate excitatory input onto pyramidal neurons within cortical microcircuits. Experimentally reducing the function of these neurons affects excitatory signal-to-noise ratio, reduces synchronized cellular and neural activity, and leads to cognitive dysfunctions. Conversely, augmenting SST+ cell post-synaptic α5-GABA-A receptor activity has pro-cognitive efficacy in stress and aging models. Together, this suggests that reduced signaling of the SST+ neuron/α5-GABA-A receptor pathway contributes to cognitive dysfunctions, and that it represents a novel therapeutic target for remediating mood and cognitive symptoms in depression, other psychiatric disorders and during aging.

Acetylcholine and Spontaneous Recognition Memory in Rodents and Primates

Whilst acetylcholine has long been linked to memory, there have been significant questions about its specific role. In particular, the effects of cholinergic manipulations in primates and rodents has often been at odds. Here, we review the work in primates and rodents on the specific function of acetylcholine in memory, and episodic memory in particular. We propose that patterns of impairment can best be understood in terms of a role for hippocampal acetylcholine in resolving spatial interference and we discuss the benefits of new tasks of episodic memory in animals allowing clearer translation of findings to the clinic.

Resveratrol oligomers from Paeonia suffruticosa protect mice against cognitive dysfunction by regulating cholinergic, antioxidant and anti-inflammatory pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Paeonia suffruticosa Andr. has been widely used in traditional Chinese medicine as an anti-tumour, anti-oxidant, anti-inflammatory and neuroprotective agent. Resveratrol oligomers are the main components of the seed coat extracts of Paeonia suffruticosa (PSCE) and have DPPH free radical scavenging and β-secretase inhibitory activity. However, studies of its effect on ameliorating cognitive deficits are limited, and analyses of the underlying mechanisms are insufficient.

AIM OF STUDY

This study aimed to investigate the cholinesterase inhibitory activities of resveratrol oligomers from P. suffruticosa in vitro and their effects on diminishing the oxygen-glucose deprivation/reoxygenation (OGD/R) -induced cytotoxicity in PC12 cells and scopolamine-induced cognitive deficits in mice. Moreover, the underlying mechanisms were further explored.

MATERIALS AND METHODS

In vitro, the inhibitory effects of PSCE and its 10 stilbenes on acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) were evaluated using the Ellman's assay, and its protective effects on normal and OGD/R-injured PC12 cells were evaluated using the MTT assay. For the in vivo assay, C57BL/6 mice were orally administered with PSCE at doses of 150 and 600 mg/kg for 28 days, and injected with scopolamine (1.5 mg/kg) to induce cognitive deficits. The memory behaviours were evaluated using the novel object recognition, Morris water maze and inhibitory avoidance test. Levels of various biochemical markers were also examined, including AChE, choline acetyltransferase (ChAT), acetylcholine (ACh), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) in the mouse brain and interleukin-1β (IL-1β), interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), interleukin-4 (IL-4) in serum.

RESULTS

PSCE and its 10 stilbenes display good inhibition of AChE and BuChE activities and significantly increase the viability of normal and OGD/R-injured PC12 cells. PSCE improves the cognitive performance of scopolamine-treated mice in behavioural tests. Meanwhile, PSCE increases AChE, ChAT, SOD, and CAT activities and ACh, GSH, IL-4 levels, and decreases IL-1β, IL-6, TNF-α levels in the model animals.

CONCLUSIONS

Resveratrol oligomers from P. suffruticosa show neuroprotective effect in vitro and in vivo by regulating cholinergic, antioxidant and anti-inflammatory pathways, may have promising application in the treatment of Alzheimer's disease.

Bidirectional regulation of distinct memory domains by α5-subunit-containing GABAA receptors in CA1 pyramidal neurons

Reduction in the expression or function of α5-subunit-containing GABA_A receptors (α5GABA_ARs) leads to improvement in several hippocampus-dependent memory domains. However, studies thus far mostly lack anatomical specificity in terms of neuronal circuits and populations. We demonstrate that mice with a selective knockdown of α5GABA_ARs in CA1 pyramidal neurons (α5CA1KO mice) show improved spatial and trace fear-conditioning memory. Unexpectedly, α5CA1KO mice were comparable to controls in contextual fear-conditioning but showed an impairment in context discrimination, suggesting fine-tuning of activity in CA1 pyramidal cell dendrites through α5-mediated inhibition might be necessary for distinguishing highly similar contexts.

Electroacupuncture Improved Chronic Cerebral Hypoperfusion-Induced Anxiety-Like Behavior and Memory Impairments in Spontaneously Hypertensive Rats by Downregulating the ACE/Ang II/AT1R Axis and Upregulating the ACE2/Ang-(1-7)/MasR Axis

Electroacupuncture (EA) can effectively alleviate anxiety disorders and memory impairments caused by various neurodegenerative diseases; however, the molecular mechanisms underlying its neuroprotective effects are unclear. Previous studies have shown that the renin-angiotensin system (RAS) comprises of two axes with mutual antagonism: the classical angiotensin converting enzyme/angiotensin II/angiotensin II type 1 receptor (ACE/Ang II/AT1R) axis and the protective angiotensin converting enzyme 2/angiotensin-(1-7)/Mas receptor (ACE2/Ang-(1-7)/MasR) axis. In this study, we observed that chronic cerebral hypoperfusion (CCH) mediated anxiety-like behavior and memory impairments in spontaneously hypertensive rats (SHR) via upregulation of the hippocampal classical axis (ACE/Ang II/AT1R) and the partial hippocampal protective axis (ACE2/Ang-(1-7)). However, Ang II levels were much higher than those of Ang-(1–7), indicating that the ACE/Ang II/AT1R axis plays a dominant role in the comorbidity of CCH and hypertension. Moreover, candesartan cilexetil (Canc) and perindopril (Peril) were used as positive control drugs. We found that EA, Canc, and Peril attenuated CCH-induced anxiety-like behavior and memory impairments in SHR, potentially via downregulation of the hippocampal classical axis (ACE/Ang II/AT1R) and upregulation of the whole hippocampal protective axis (ACE2/Ang-(1-7)/MasR). These results suggest that EA therapy for CCH with hypertension may be mediated by two hippocampal RAS axes.

Novel Benzodiazepine-Like Ligands with Various Anxiolytic, Antidepressant, or Pro-Cognitive Profiles

Altered gamma-aminobutyric acid (GABA) function is consistently reported in psychiatric disorders, normal aging, and neurodegenerative disorders and reduced function of GABA interneurons is associated with both mood and cognitive symptoms. Benzodiazepines (BZ) have broad anxiolytic, but also sedative, anticonvulsant and amnesic effects, due to nonspecific GABA-A receptor (GABAA-R) targeting. Varying the profile of activity of BZs at GABAA-Rs is predicted to uncover additional therapeutic potential. We synthesized four novel imidazobenzodiazepine (IBZD) amide ligands and tested them for positive allosteric modulation at multiple α-GABAA-R (α-positive allosteric modulators), pharmacokinetic properties, as well as anxiolytic and antidepressant activities in adult mice. Efficacy at reversing stress-induced or age-related working memory deficits was assessed using a spontaneous alternation task. Diazepam (DZP) was used as a control. Three ligands (GL-II-73, GL-II-74, and GL-II-75) demonstrated adequate brain penetration and showed predictive anxiolytic and antidepressant efficacies. GL-II-73 and GL-II-75 significantly reversed stress-induced and age-related working memory deficits. In contrast, DZP displayed anxiolytic but no antidepressant effects or effects on working memory. We demonstrate distinct profiles of anxiolytic, antidepressant, and/or pro-cognitive activities of newly designed IBZD amide ligands, suggesting novel therapeutic potential for IBZD derivatives in depression and aging.

JM-20 protects memory acquisition and consolidation on scopolamine model of cognitive impairment

OBJECTIVE

JM-20, a novel hybrid synthetic molecule, has been reported to have antioxidant, mitoprotective, anti-excitotoxic, anti-apoptotic and anti-inflammatory properties. However, the neuroprotective effect of JM-20 against memory impairment in preclinical AD-like models has not been analyzed. The aim of this study was to evaluate the potential neuroprotection of JM-20 that preserves essential memory process from cholinergic dysfunction and other molecular damages.

METHODS

The effects of JM-20 on scopolamine (1 mg/kg)-induced cognitive disorders were studied. Male Wistar rats (220-230 g) were treated with JM-20 and/or scopolamine, and behavioral tasks were performed. The AChE activity, superoxide dismutase activity, catalase activity, MDA and T-SH level on brain tissue were determined by spectrophotometric methods. Mitochondrial functionality parameters were measured after behavioral tests. Histological analyses on hippocampus and prefrontal cortex were processed with hematoxylin and eosin, and neuronal and axonal damage were determined.

RESULTS

The behavioral, biochemical and histopathological studies revealed that oral pre-treatment with JM-20 (8 mg/kg) significantly attenuated the scopolamine-induced memory deficits, mitochondrial malfunction, oxidative stress, and prevented AChE hyperactivity probably due to specific inhibition of AChE enzyme. It was also observed marked histological protection on hippocampal and prefrontal-cortex regions.

CONCLUSIONS

The multimodal action of this molecule could mediate the memory protection here observed and suggest that it may modulate different pathological aspects of memory deficits associated with AD in humans.

Neuroprotective effects of matrine on scopolamine-induced amnesia via inhibition of AChE/BuChE and oxidative stress

The present study was designed to evaluate the effects of matrine (MAT) on scopolamine (SCOP)-induced learning and memory impairment. After successive oral administration of MAT to mice for three days at doses of 0.4, 2, and 10 mg/kg, we assessed improvements in learning and memory and investigated the mechanism of action of SCOP-induced amnesia. Donepezil at a dose of 3 mg/kg was used as a standard memory enhancer. MAT significantly improved SCOP-induced learning and memory impairment in novel object recognition and Y-maze tests at doses of 0.4, 2, and 10 mg/kg. Furthermore, MAT inhibited acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities and decreased oxidative stress in the brain, as evidenced by increased total antioxidant capacity, total superoxide dismutase levels, and catalase activities as well as decreased malondialdehyde levels. Additionally, there was a significant negative correlation between the percentage of spontaneous alternation in the Y maze and AChE activity in the cortex and hippocampus. MAT ameliorated SCOP-induced amnesia by the inhibition of both AChE/BuChE activities and oxidative stress. This study provides further evidence to encourage the development of MAT as a drug for the prevention or treatment of Alzheimer's disease.

Substituted Aminobenzothiazole Derivatives of Tacrine: Synthesis and Study on Learning and Memory Impairment in Scopolamine-Induced Model of Amnesia in Rat

BACKGROUND

Currently, there is no conclusive cure for Alzheimer's disease (AD) and existing treatments mainly offer symptomatic relief. Dysfunction of the cholinergic system plays an important role in the pathogenesis of AD. Tacrine (1, 2, 3, 4-tetrahydroacridin-9-amine, III) was the first approved agent for the palliative therapy of AD but its use is associated with some complications. Development of novel multi target derivatives of Tacrine with lower complications is strongly warranted. In this study, new aminobenzothiazole (1-5, with many useful biological and pharmacological properties) analogues (IV-VIII) were synthesized by changing of amine moiety of III. Then, the effects of these new compounds on learning and memory impairment in scopolamine-induced model of amnesia were studied and the outcomes were compared with control and Tacrine groups in rat.

MATERIAL AND METHODS

The rats received Tacrine or its derivatives (IV-VIII) i.p. for two weeks at a dose of 10 mg/kg. For induction of amnesia, scopolamine at a dose of 1 mg/kg was daily administered i.p. started on day-8 till the end of the study. Behavioral experiments including Y-maze, novel object recognition (discrimination) and passive avoidance paradigms were conducted at week 2.

RESULTS

Data analysis showed that some Tacrine derivatives, especially VII with 2-amino, 6-nitrobenzothiazole moiety, could markedly and significantly improve alternation score, discrimination ratio and step through latency compared to control and Tacrine groups.

CONCLUSION

These findings indicated that some of these derivatives (especially compounds VI and VII) are capable to mitigate learning and memory deficits in scopolamine-induced model of amnesia in rats and may have potential benefit in management of patients with AD.

Persistent therapeutic effect of a novel α5-GABAA receptor antagonist in rodent preclinical models of vascular cognitive impairment

This study examined the potential of the selective extra-synaptic α5-GABA_A receptor inhibitor S44819 (Egis-13529) to improve cognitive performance in preclinical models of vascular cognitive impairment (VCI). Chronic hypoperfusion of the brain in mice was induced by permanent occlusion of the right common carotid artery (rUCO). rUCO induced impairments of cognitive function in the object recognition test (OR) and the rewarded T-maze (RTM). In both tests, a single oral treatment with S44819 (OR - 0.1-3 mg/kg, RTM - 1-3 mg/kg p.o.) significantly reduced the effect of rUCO. Long-term treatment with S44819 (1-10 mg/kg twice daily p.o. for 14 days), that was initiated 24 h after surgery and was followed by a 10- or 13-day wash-out period, fully prevented the decline of cognitive performance of rUCO mice. In rats, occlusion of the middle cerebral artery (MCA) for 30 min caused a significantly diminished performance in the OR. This was prevented by S44819 given p.o. 15 mg/kg twice daily for 8 days, starting 7 days after surgery and tested following a 7-day wash-out period. Taken together, S44819 markedly and stably improved reference and working memory impaired by rUCO in mice. In rats, the compound effectively suppressed the development of cognitive impairment after mild stroke. In conclusion, as longer-term administration led to a persistent reversal of the cognitive deficits, it appears that S44819 may have symptomatic, as well as disease-modifying effects in models of VCI. Proof of concept is therefore provided for testing S44819 in the therapy of VCI and post-stroke dementia in humans.

GABAergic inhibitory neurons as therapeutic targets for cognitive impairment in schizophrenia

Schizophrenia is considered primarily as a cognitive disorder. However, functional outcomes in schizophrenia are limited by the lack of effective pharmacological and psychosocial interventions for cognitive impairment. GABA (gamma-aminobutyric acid) interneurons are the main inhibitory neurons in the central nervous system (CNS), and they play a critical role in a variety of pathophysiological processes including modulation of cortical and hippocampal neural circuitry and activity, cognitive function-related neural oscillations (eg, gamma oscillations) and information integration and processing. Dysfunctional GABA interneuron activity can disrupt the excitatory/inhibitory (E/I) balance in the cortex, which could represent a core pathophysiological mechanism underlying cognitive dysfunction in schizophrenia. Recent research suggests that selective modulation of the GABAergic system is a promising intervention for the treatment of schizophrenia-associated cognitive defects. In this review, we summarized evidence from postmortem and animal studies for abnormal GABAergic neurotransmission in schizophrenia, and how altered GABA interneurons could disrupt neuronal oscillations. Next, we systemically reviewed a variety of up-to-date subtype-selective agonists, antagonists, positive and negative allosteric modulators (including dual allosteric modulators) for α5/α3/α2 GABA_A and GABA_B receptors, and summarized their pro-cognitive effects in animal behavioral tests and clinical trials. Finally, we also discuss various representative histone deacetylases (HDAC) inhibitors that target GABA system through epigenetic modulations, GABA prodrug and presynaptic GABA transporter inhibitors. This review provides important information on current potential GABA-associated therapies and future insights for development of more effective treatments.

Hippocampal GABAA antagonism reverses the novel object recognition deficit in sub-chronic phencyclidine-treated rats

BACKGROUND

Abnormalities in prefrontal cortical and hippocampal GABAergic function are postulated to be major causes of the cognitive impairment associated with schizophrenia (CIAS). There are conflicting views on whether diminished or enhanced GABAergic activity contributes to the deficit in short-term novel object recognition (NOR) in the sub-chronic phencyclidine (scPCP) rodent model of CIAS. This study assessed the role of GABA_A signaling in the medial prefrontal cortex (mPFC) and ventral hippocampus (vHPC) in NOR in saline (scSAL)- and scPCP-treated rats.

METHODS

The effects of local administration of a GABA_A agonist (muscimol) into the vHPC or mPFC and an antagonist (bicuculline) or a GABA_A/benzodiazepine partial agonist (bretazenil) into the vHPC on NOR in scSAL and scPCP-treated rats were determined.

RESULTS

In scSAL-treated rats, injection of muscimol into the vHPC, but not mPFC, induced a deficit in NOR. The scPCP-induced NOR deficit was significantly reversed by intra-vHPC bicuculline, while intra-vHPC bretazenil produced a non-significant trend for reversal (p = .06). scPCP treatment increased mRNA expression of GABA_A γ₂ in PFC and GABA_A α₅ and GABA_A β₁ in the HPC. However, GABA concentration in the PFC or HPC was not altered.

CONCLUSIONS

These findings indicate that the scPCP-induced NOR deficit can be rescued by reducing GABA_A receptor stimulation in vHPC, indicating that increased vHPC GABA_A inhibition may contribute to the scPCP-induced NOR deficit in rats. These results also indicate that excessive GABA_A receptor signalling in the vHPC has a deleterious effect on NOR in normal rats.

Short-term and long-term effects of diazepam on the memory for discrimination and generalization of scopolamine

Benzodiazepines are among the most widely prescribed and misused psychopharmaceutical drugs. Although they are well-tolerated, they are also capable of producing amnestic effects similar to those observed after pharmacological or organic cholinergic dysfunction. To date, the effect of benzodiazepine diazepam on the memory for discrimination of anticholinergic drugs has not been reported. The aim of the present study was to analyze the immediate and long-term effects of diazepam on a drug discrimination task with scopolamine. Male Wistar rats were trained to discriminate between scopolamine and saline administration using a two-lever discrimination task. Once discrimination was acquired, the subjects were divided into three independent groups, (1) control, (2) diazepam, and (3) diazepam chronic administration (10 days). Subsequently, generalization curves for scopolamine were obtained. Additionally, the diazepam and control groups were revaluated after 90 days without having been given any other treatment. The results showed that diazepam produced a significant reduction in the generalization gradient for scopolamine, indicating an impairment of discrimination. The negative effect of diazepam persisted even 90 days after drug had been administered. Meanwhile, the previous administration of diazepam for 10 days totally abated the generalization curve and the general performance of the subjects. The results suggest that diazepam affects memory for the stimulus discrimination of anticholinergic drugs and does so persistently, which could be an important consideration during the treatment of amnesic patients with benzodiazepines.

Selective inhibition of extra-synaptic α5-GABAA receptors by S44819, a new therapeutic agent

In the mammalian central nervous system (CNS) GABA_A receptors (GABA_ARs) mediate neuronal inhibition and are important therapeutic targets. GABA_ARs are composed of 5 subunits, drawn from 19 proteins, underpinning expression of 20-30 GABA_AR subtypes. In the CNS these isoforms are heterogeneously expressed and exhibit distinct physiological and pharmacological properties. We report the discovery of S44819, a novel tricyclic oxazolo-2,3-benzodiazepine-derivative, that selectively inhibits α5-subunit-containing GABA_ARs (α5-GABA_ARs). Current α5-GABA_AR inhibitors bind to the "benzodiazepine site". However, in HEK293 cells expressing recombinant α5-GABA_ARs, S44819 had no effect on ³H-flumazenil binding, but displaced the GABA_AR agonist ³H-muscimol and competitively inhibited the GABA-induced responses. Importantly, we reveal that the α5-subunit selectivity is uniquely governed by amino acid residues within the α-subunit F-loop, a region associated with GABA binding. In mouse hippocampal CA1 neurons, S44819 enhanced long-term potentiation (LTP), blocked a tonic current mediated by extrasynaptic α5-GABA_ARs, but had no effect on synaptic GABA_ARs. In mouse thalamic neurons, S44819 had no effect on the tonic current mediated by δ-GABA_ARs, or on synaptic (α1β2γ2) GABA_ARs. In rats, S44819 enhanced object recognition memory and reversed scopolamine-induced impairment of working memory in the eight-arm radial maze. In conclusion, S44819 is a first in class compound that uniquely acts as a potent, competitive, selective antagonist of recombinant and native α5-GABA_ARs. Consequently, S44819 enhances hippocampal synaptic plasticity and exhibits pro-cognitive efficacy. Given this profile, S44819 may improve cognitive function in neurodegenerative disorders and facilitate post-stroke recovery.

Mitochondrial involvement in memory impairment induced by scopolamine in rats

OBJECTIVE

Scopolamine (SCO) administration to rats induces molecular features of AD and other dementias, including impaired cognition, increased oxidative stress, and imbalanced cholinergic transmission. Although mitochondrial dysfunction is involved in different types of dementias, its role in cognitive impairment induced by SCO has not been well elucidated. The aim of this work was to evaluate the in vivo effect of SCO on different brain mitochondrial parameters in rats to explore its neurotoxic mechanisms of action.

METHODS

Saline (Control) or SCO (1 mg/kg) was administered intraperitoneally 30 min prior to neurobehavioral and biochemical evaluations. Novel object recognition and Y-maze paradigms were used to evaluate the impact on memory, while redox profiles in different brain regions and the acetylcholinesterase (AChE) activity of the whole brain were assessed to elucidate the amnesic mechanism of SCO. Finally, the effects of SCO on brain mitochondria were evaluated both ex vivo and in vitro, the latter to determine whether SCO could directly interfere with mitochondrial function.

RESULTS

SCO administration induced memory deficit, increased oxidative stress, and increased AChE activities in the hippocampus and prefrontal cortex. Isolated brain mitochondria from rats administered with SCO were more vulnerable to mitochondrial swelling, membrane potential dissipation, H₂O₂ generation and calcium efflux, all likely resulting from oxidative damage. The in vitro mitochondrial assays suggest that SCO did not affect the organelle function directly.

CONCLUSION

In conclusion, the present results indicate that SCO induced cognitive dysfunction and oxidative stress may involve brain mitochondrial impairment, an important target for new neuroprotective compounds against AD and other dementias.

SB203580 reverses memory deficits and depression-like behavior induced by microinjection of Aβ1-42 into hippocampus of mice

A high co-morbidity between Alzheimer's disease (AD) and depression suggests there might be similar mechanisms underlying the course of these diseases. Previous studies have shown that p38MAPK plays a critical role in the pathophysiology of AD and depression. However, little is known about whether SB203580, a selective inhibitor of p38MAPK, may protect against AD-associated cognitive impairments and depression-like behavior, simultaneously. Herein, we have shown, for the first time, that SB203580 may reverse memory impairments and depression-like behavior induced by hippocampal infusion of β-amyloid 1-42 (Aβ_1-42), as measured by novel object recognition, Morris water maze, tail-suspension and forced-swimming tests. In addition, phorbol 12-myristate 13-acetate (PMA), a PKC activator which also activates p38MAPK, significantly abolished the effects of SB203580. Moreover, Aβ_1-42 causes increased phosphorylation of p38MAPK and decreased phosphorylation of Ser9-glycogen synthase kinase 3β (GSK3β) and cAMP-response element binding protein (CREB) in the hippocampus of mice, which could be significantly reversed by SB203580. Our results suggest that SB203580 reversed Aβ_1-42-induced cognitive impairments and depression-like behavior via inhibiting p38MAPK signaling pathway, which not only supports p38MAPK as a therapeutic target for AD-associated cognitive dysfunction and depression-like behavior, but also provides experimental basis for the use of SB203580 in co-morbidity of AD and depression.

Effects of formaldehyde exposure on anxiety-like and depression-like behavior, cognition, central levels of glucocorticoid receptor and tyrosine hydroxylase in mice

Formaldehyde exposure is toxic to the brains of mammals, but the mechanism remains unclear. We investigated the effects of inhaled formaldehyde on anxiety, depression, cognitive capacity and central levels of glucocorticoid receptor and tyrosine hydroxylase in mice. After exposure to 0, 1 or 2 ppm gaseous formaldehyde for one week, we measured anxiety-like behavior using open field and elevated plus-maze tests, depression-like behavior using a forced swimming test, learning and memory using novel object recognition tests, levels of glucocorticoid receptors in the hippocampus and tyrosine hydroxylase in the Arc, MPOA, ZI and VTA using immuhistochemistry. We found that inhalation of 1 ppm formaldehyde reduced levels of anxiety-like behavior. Inhalation of 2 ppm formaldehyde reduced body weight, but increased levels of depression-like behavior, impaired novel object recognition, and lowered the numbers of glucocorticoid receptor immonureactive neurons in the hippocampus and tyrosine hydroxylase immonureactive neurons in the ventral tegmental area and the zona incerta, medial preoptic area. Different concentrations of gaseous formaldehyde result in different effects on anxiety, depression-like behavior and cognition ability which may be associated with alterations in hippocampal glucocorticoid receptors and brain tyrosine hydroxylase levels.

A Review of the Updated Pharmacophore for the Alpha 5 GABA(A) Benzodiazepine Receptor Model

An updated model of the GABA(A) benzodiazepine receptor pharmacophore of the α5-BzR/GABA(A) subtype has been constructed prompted by the synthesis of subtype selective ligands in light of the recent developments in both ligand synthesis, behavioral studies, and molecular modeling studies of the binding site itself. A number of BzR/GABA(A) α5 subtype selective compounds were synthesized, notably α5-subtype selective inverse agonist PWZ-029 (1) which is active in enhancing cognition in both rodents and primates. In addition, a chiral positive allosteric modulator (PAM), SH-053-2′F-R-CH₃ (2), has been shown to reverse the deleterious effects in the MAM-model of schizophrenia as well as alleviate constriction in airway smooth muscle. Presented here is an updated model of the pharmacophore for α5β2γ2 Bz/GABA(A) receptors, including a rendering of PWZ-029 docked within the α5-binding pocket showing specific interactions of the molecule with the receptor. Differences in the included volume as compared to α1β2γ2, α2β2γ2, and α3β2γ2 will be illustrated for clarity. These new models enhance the ability to understand structural characteristics of ligands which act as agonists, antagonists, or inverse agonists at the Bz BS of GABA(A) receptors.

Innovative mechanisms of action for pharmaceutical cognitive enhancement: A systematic review

Pharmacological cognitive enhancement refers to improvement in cognitive functions after drug use in healthy individuals. This popular topic attracts attention both from the general public and the scientific community. The objective was to explore innovative mechanisms of psychostimulant's action, whose potential effectiveness was assessed in randomized placebo-controlled trials (RCTs). A systematic review was carried out, using the words "attention", "memory", "learning", "executive functions", and "vigilance/wakefulness" combined to "cognitive enhancer" or "smart drug". Methylphenidate, amphetamines, modafinil, nicotine, acetylcholine esterase inhibitors and antidepressants were extensively studied in previous meta-analyses and were not included in the present work. Drugs were classified according to their primary mode of action, namely catecholaminergic drugs (tolcapone, pramipexole, guanfacine), cholinergic drugs (anticholinergics), glutamatergic drugs (ampakines), histaminergic drugs, and non-specified (glucocorticoids). Overall, 50 RCTs were included in the present review. In conclusion, a number of new active drugs were found to improve some cognitive functions, in particular verbal episodic memory. However the number of RCTs was limited, and most of the studies found negative results. Future studies should assess both effectiveness and tolerance of repeated doses administration, and individual variability in dose response (including baseline characteristics and potential genetic polymorphisms). One explanation for the limited number of recent RCTs with new psychostimulants seems to be the ethical debate surrounding pharmaceutical cognitive enhancement in healthy subjects.

Negative modulation of α₅ GABAA receptors in rats may partially prevent memory impairment induced by MK-801, but not amphetamine- or MK-801-elicited hyperlocomotion

Reportedly, negative modulation of α5 GABAA receptors may improve cognition in normal and pharmacologically-impaired animals, and such modulation has been proposed as an avenue for treatment of cognitive symptoms in schizophrenia. This study assessed the actions of PWZ-029, administered at doses (2, 5, and 10 mg/kg) at which it reached micromolar concentrations in brain tissue with estimated free concentrations adequate for selective modulation of α5 GABAA receptors, in three cognitive tasks in male Wistar rats acutely treated with the noncompetitive N-methyl-d-aspartate receptor antagonist, MK-801 (0.1 mg/kg), as well in tests of locomotor activity potentiated by MK-801 (0.2 mg/kg) or amphetamine (0.5 mg/kg). In a hormetic-like manner, only 5 mg/kg PWZ-029 reversed MK-801-induced deficits in novel object recognition test (visual recognition memory), whereas in the Morris water maze, the 2 mg/kg dose of PWZ-029 exerted partial beneficial effects on spatial learning impairment. PWZ-029 did not affect recognition memory deficits in social novelty discrimination procedure. Motor hyperactivity induced with MK-801 or amphetamine was not preventable by PWZ-029. Our results show that certain MK-801-induced memory deficits can be ameliorated by negative modulation of α5 GABAA receptors, and point to the need for further elucidation of their translational relevance to cognitive deterioration in schizophrenia.

A novel GABA(A) alpha 5 receptor inhibitor with therapeutic potential

Novel 2,3-benzodiazepine and related isoquinoline derivatives, substituted at position 1 with a 2-benzothiophenyl moiety, were synthesized to produce compounds that potently inhibited the action of GABA on heterologously expressed GABAA receptors containing the alpha 5 subunit (GABAA α5), with no apparent affinity for the benzodiazepine site. Substitutions of the benzothiophene moiety at position 4 led to compounds with drug-like properties that were putative inhibitors of extra-synaptic GABAA α5 receptors and had substantial blood-brain barrier permeability. Initial characterization in vivo showed that 8-methyl-5-[4-(trifluoromethyl)-1-benzothiophen-2-yl]-1,9-dihydro-2H-[1,3]oxazolo[4,5-h][2,3]benzodiazepin-2-one was devoid of sedative, pro-convulsive or motor side-effects, and enhanced the performance of rats in the object recognition test. In summary, we have discovered a first-in-class GABA-site inhibitor of extra-synaptic GABAA α5 receptors that has promising drug-like properties and warrants further development.

Behavioral effects of the benzodiazepine-positive allosteric modulator SH-053-2'F-S-CH₃ in an immune-mediated neurodevelopmental disruption model

BACKGROUND

Impaired γ-aminobutyric acid (GABA) signaling may contribute to the emergence of cognitive deficits and subcortical dopaminergic hyperactivity in patients with schizophrenia and related psychotic disorders. Against this background, it has been proposed that pharmacological interventions targeting GABAergic dysfunctions may prove useful in correcting such cognitive impairments and dopaminergic imbalances.

METHODS

Here, we explored possible beneficial effects of the benzodiazepine-positive allosteric modulator SH-053-2'F-S-CH₃, with partial selectivity at the α2, α3, and α5 subunits of the GABAA receptor in an immune-mediated neurodevelopmental disruption model. The model is based on prenatal administration of the viral mimetic polyriboinosinic-polyribocytidilic acid [poly(I:C)] in mice, which is known to capture various GABAergic, dopamine-related, and cognitive abnormalities implicated in schizophrenia and related disorders.

RESULTS

Real-time polymerase chain reaction analyses confirmed the expected alterations in GABAA receptor α subunit gene expression in the medial prefrontal cortices and ventral hippocampi of adult poly(I:C) offspring relative to control offspring. Systemic administration of SH-053-2'F-S-CH₃ failed to normalize the poly(I:C)-induced deficits in working memory and social interaction, but instead impaired performance in these cognitive and behavioral domains both in control and poly(I:C) offspring. In contrast, SH-053-2'F-S-CH₃ was highly effective in mitigating the poly(I:C)-induced amphetamine hypersensitivity phenotype without causing side effects in control offspring.

CONCLUSIONS

Our preclinical data suggest that benzodiazepine-like positive allosteric modulators with activity at the α2, α3, and α5 subunits of the GABAA receptor may be particularly useful in correcting pathological overactivity of the dopaminergic system, but they may be ineffective in targeting multiple pathological domains that involve the co-existence of psychotic, social, and cognitive dysfunctions.

Allosteric modulation of GABA(A) receptor subtypes:effects on visual recognition and visuospatial working memory in rhesus monkeys [corrected]

Non-selective positive allosteric modulators (PAMs) of GABAA receptors (GABAARs) are known to impair anterograde memory. The role of the various GABAAR subtypes in the memory-impairing effects of non-selective GABAAR PAMs has not been fully elucidated. The current study assessed, in rhesus monkeys, effects of modulation of α1, α2/3, and α5GABAARs on visual recognition and spatial working memory using delayed matching-to-sample (DMTS) and self-ordered spatial search (SOSS) procedures, respectively. The DMTS procedure (n=8) involved selecting a previously presented 'sample' image from a set of multiple images presented after a delay. The SOSS procedure (n=6) involved touching a number of boxes without repeats. The non-selective GABAAR PAM triazolam and the α1GABAA preferential PAMS zolpidem and zaleplon reduced accuracy in both procedures, whereas the α5GABAA preferential PAMs SH-053-2'F-R-CH3 and SH-053-2'F-S-CH3, and the α2/3GABAA preferential PAM TPA023B were without effects on accuracy or trial completion. The low-efficacy α5GABAAR negative allosteric modulator (NAM) PWZ-029 slightly increased only DMTS accuracy, whereas the high-efficacy α5GABAAR NAMs RY-23 and RY-24 did not affect accuracy under either procedure. Finally, the slopes of the accuracy dose-effect curves for triazolam, zolpidem, and zaleplon increased with box number in the SOSS procedure, but were equivalent across DMTS delays. The present results suggest that (1) α1GABAARs, compared with α2/3 and α5GABAARs, are primarily involved in the impairment, by non-selective GABAAR PAMs, of visual recognition and visuospatial working memory in nonhuman primates; and (2) relative cognitive impairment produced by positive modulation of GABAARs increases with number of locations to be remembered, but not with the delay for remembering.

The monoaminergic stabilizer (-)-OSU6162 reverses delay-dependent natural forgetting and improves memory impairment induced by scopolamine in mice

The aim of the present study was to evaluate the effect of the monoaminergic stabilizer (-)-OSU6162 on spatial recognition memory. Male NMRI mice were tested in the object location model which is based on the animals' inherent interest to examine changes in their environment: The animals' propensity to explore relocated objects in relation to unaltered objects, presented in two different sessions (sample and trial), was studied. In a first series of experiments the effect of (-)-OSU6162 on natural forgetting was evaluated. With an inter-session interval (ISI) of 30 min or an hour, untreated mice spent longer time exploring the displaced object, but when the time between sessions was as long as 6 h, the mice did not identify the displaced object. However, using the 6 h ISI design we found that (-)-OSU6162 in doses up to 30 μmol/kg, given directly after the sample session, caused an increased interest for the displaced object. Twenty-four hours after administration, (-)-OSU6162 was still effective in facilitating identification of the displaced object. We also evaluated the effect of (-)-OSU6162 on scopolamine-induced memory deficits in this model - the two agents were given 30 min before the sample session and the ISI was one hour. Under these conditions scopolamine induced a deficit in object location memory and this effect was counteracted by (-)-OSU6162. The data from the present study suggest that (-)-OSU6162 prolongs object location memory in normal mice and reverses scopolamine-induced memory deficits. (-)-OSU6162 might be a valuable drug candidate for memory deficits and other cognitive impairments.