Modulation of nitrergic signalling pathway by American ginseng attenuates chronic unpredictable stress-induced cognitive impairment, neuroinflammation, and biochemical alterations

Psychosocial experiences are associated with human brain mitochondrial biology

Psychosocial experiences affect brain health and aging trajectories, but the molecular pathways underlying these associations remain unclear. Normal brain function relies on energy transformation by mitochondria oxidative phosphorylation (OxPhos). Two main lines of evidence position mitochondria both as targets and drivers of psychosocial experiences. On the one hand, chronic stress exposure and mood states may alter multiple aspects of mitochondrial biology; on the other hand, functional variations in mitochondrial OxPhos capacity may alter social behavior, stress reactivity, and mood. But are psychosocial exposures and subjective experiences linked to mitochondrial biology in the human brain? By combining longitudinal antemortem assessments of psychosocial factors with postmortem brain (dorsolateral prefrontal cortex) proteomics in older adults, we find that higher well-being is linked to greater abundance of the mitochondrial OxPhos machinery, whereas higher negative mood is linked to lower OxPhos protein content. Combined, positive and negative psychosocial factors explained 18 to 25% of the variance in the abundance of OxPhos complex I, the primary biochemical entry point that energizes brain mitochondria. Moreover, interrogating mitochondrial psychobiological associations in specific neuronal and nonneuronal brain cells with single-nucleus RNA sequencing (RNA-seq) revealed strong cell-type-specific associations for positive psychosocial experiences and mitochondria in glia but opposite associations in neurons. As a result, these "mind-mitochondria" associations were masked in bulk RNA-seq, highlighting the likely underestimation of true psychobiological effect sizes in bulk brain tissues. Thus, self-reported psychosocial experiences are linked to human brain mitochondrial phenotypes.

Improvement of cognitive dysfunction by a novel phosphodiesterase type 5 inhibitor, Tadalafil

There is substantial evidence for the modulatory role of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterases (PDEs) in memory and synaptic plasticity, and an increase in intracellular cGMP facilitates these processes. The present study was aimed at the neuropharmacological investigations of tadalafil (TAD 5, 10, and 20 mg/kg, p.o.) and further involvement of nitric oxide (NO)-cGMP in its effects. The effects of tadalafil and its combination with N^G -nitro-L-arginine methyl ester (L-NAME) were investigated in scopolamine- and diabetes-induced cognitive dysfunction using elevated plus maze (EPM) and object recognition (ORT) tests. The results of EPM revealed that the scopolamine- and diabetes-induced learning and memory deficit was dose dependently attenuated after administration of TAD (TAD 10 and 20 mg/kg, p.o.) in both paradigms studied. Administration of L-NAME (20 mg/kg) aggravated scopolamine- and diabetes-induced learning and memory deficit. Co-administration of L-NAME (20 mg/kg) after TAD (20 mg/kg) produced significant increase in cognitive performance as compared to scopolamine- and diabetic- control group. This showed that L-NAME (20 mg/kg) aggravated scopolamine- and diabetes-induced learning and memory deficit was significantly reversed by TAD (20 mg/kg). The results of the present study revealed that tadalafil by inhibiting PDE5 possibly elevated the cGMP level that through a diversity of its substrates produced neuropharmacological effects in cognitive dysfunction.

Ginsenoside and Its Therapeutic Potential for Cognitive Impairment

Cognitive impairment (CI) is one of the major clinical features of many neurodegenerative diseases. It can be aging-related or even appear in non-central nerve system (CNS) diseases. CI has a wide spectrum that ranges from the cognitive complaint with normal screening tests to mild CI and, at its end, dementia. Ginsenosides, agents extracted from a key Chinese herbal medicine (ginseng), show great promise as a new therapeutic option for treating CI. This review covered both clinical trials and preclinical studies to summarize the possible mechanisms of how ginsenosides affect CI in different diseases. It shows that ginsenosides can modulate signaling pathways associated with oxidative stress, apoptosis, inflammation, synaptic plasticity, and neurogenesis. The involved signaling pathways mainly include the PI3K/Akt, CREB/BDNF, Keap1/Nrf2 signaling, and NF-κB/NLRP3 inflammasome pathways. We hope to provide a theoretical basis for the treatment of CI for related diseases by ginsenosides.

Mini-review: Brain energy metabolism and its role in animal models of depression, bipolar disorder, schizophrenia and autism

Mitochondria are cellular organelles essential for energy metabolism and antioxidant defense. Mitochondrial impairment is implicated in many psychiatric disorders, including depression, bipolar disorder, schizophrenia, and autism. To characterize and eventually find effective treatments of bioenergetic impairment in psychiatric disease, researchers find animal models indispensable. The present review focuses on brain energetics in several environmental, genetic, drug-induced, and surgery-induced animal models of depression, bipolar disorder, schizophrenia, and autism. Most reported deficits included decreased activity in the electron transport chain, increased oxidative damage, decreased antioxidant defense, decreased ATP levels, and decreased mitochondrial potential. Models of depression, bipolar disorder, schizophrenia, and autism shared many bioenergetic deficits. This is in concordance with the absence of a disease-specific brain energy phenotype in human patients. Unfortunately, due to the absence of null results in examined literature, indicative of reporting bias, we refrain from making generalized conclusions. Present review can be a valuable tool for comparing current findings, generating more targeted hypotheses, and selecting fitting models for further preclinical research.

Ginsenoside Re protects against chronic restraint stress-induced cognitive deficits through regulation of NLRP3 and Nrf2 pathways in mice

Exposure to chronic stress negatively affects the development of cognition, characterized by learning and memory decline. Ginsenoside Re (GRe), an active compound derived from Panax ginseng, exhibited neuroprotective activity in various neurological diseases. In this study, the protective effect of GRe on chronic restraint stress (CRS)-induced memory deficit was investigated. The mice were experienced 35 days of the CRS induction. The GRe was administered daily orally (10, 20, or 40 mg/kg) during the next 3 weeks stress session and the behavior test period. The CRS-induced memory impairment mice were subjected to behavioral tasks, such as the Y-maze, novel objects recognition, and step-through passive avoidance tests. Nissl staining was used to examine the neuron numbers. The levels of antioxidant enzymes, malondialdehyde, and proinflammatory factor were determined by kits and ELISA assays. The expressions of brain-derived neurotrophic factor (BDNF), NOD-like receptor protein 3 (NLRP3), nuclear factor erythroid-2 related factor 2 (Nrf2) and synapse-associated proteins (synaptophysin, SYP, and postsynaptic density 95, PSD95) were measured by Western blotting. Behavioral assessments indicated that GRe could ameliorate the cognitive impairment of CRS-induced mice, as indicated by increased responses in Y-maze (p < .05), novel objects recognition (p < .01), and step-through passive avoidance tests (p < .01). In addition, GRe treatment significantly decreased the neuronal loss in CRS mice in histological examination. Moreover, chronic GRe treatment significantly ameliorated the down-regulated the expressions of BDNF, Nrf2, heme oxygenase (HO)-1, SYP, and PSD95, as well as up-regulated NLRP3, the adaptor protein ASC, and Caspase-1 protein expression in the hippocampus of CRS-treated mice. Taken together, these findings suggest that GRe has a potential therapeutic effect on memory impairment in C57BL/6J mice exposed to CRS paradigm.

Panacis Quinquefolii Radix: A Review of the Botany, Phytochemistry, Quality Control, Pharmacology, Toxicology and Industrial Applications Research Progress

On January 2, 2020, The National Health Commission and the State Administration for Market Regulation listed Panacis Quinquefolii Radix (PQR) as a medicinal and food homologous product. PQR is the dry root of Panax quinquefolium L., which has the functions of replenishing qi and nourishing Yin, clearing heat and producing body fluid. It is often used for qi deficiency and Yin deficiency, heat exhaustion, asthma and phlegm, dry mouth and pharynx. PQR is sweet, slightly bitter and cool in nature, and enter the heart, lung and kidney meridian exerts the remedial and hygienical effect. At present, active components such as saponins, flavonoids, fatty acids, polyalkynes, volatile oils and other nutrients such as amino acids, carbohydrates, vitamins and trace elements have been isolated from PQR. Modern pharmacological studies have shown that PQR has the effects of hypoglycemic, antihypertensive, anti fatigue, anti-oxidation, anti-tumor, immunomodulatory, neuroprotective and so on. In addition, PQR is recognized as a health care product to strengthen the body and dispel diseases. It is not only the raw material of Traditional Chinese medicine preparations, but also the treasure of dietary therapy and herbal cuisine. This study not only reviewed the botany, phytochemistry and pharmacology of PQR, but also summarized its quality control, toxicity and industrial applications for the first time. This paper not only summarizes the development status of PQR, but also analyzes the shortcomings of the current research on PQR, and puts forward the corresponding solutions, in order to provide reference for future scholars to study PQR.

Methyl jasmonate reverses chronic stress-induced memory dysfunctions through modulation of monoaminergic neurotransmission, antioxidant defense system, and Nrf2 expressions

Unpredictable chronic mild stress (UCMS) has been shown to cause memory loss via increased oxidative stress and deregulation of monoaminergic and cholinergic neurotransmissions. Although the benefits of methyl jasmonate (MJ), a well-known anti-stress plant hormone against chronic stress-induced psychopathologies, have been earlier reported, its effects on antioxidant defense molecules, monoaminergic transmitters, and nuclear factor erythroid 2-related factor 2 (Nrf2) immunopositive cells have not been extensively studied. The present study was designed to examine its effect on memory functions, antioxidant biomarkers, monoaminergic transmitters, and Nrf2 immunopositive cell expression in rats exposed to UCMS. Rats received an intraperitoneal injection of MJ (10, 25, and 50 mg/kg) 30 min before exposure to UCMS daily for 28 days. Memory function was assessed on day 29 using a modified elevated plus maze and novel object recognition tests. The antioxidant biomarkers, level of monoamines (serotonin, noradrenaline, and dopamine), and Nrf2 immunopositive cell expression were determined in the rat brain tissues. The activity of cholinesterase and monoamine oxidase enzymes was also determined. MJ attenuated memory deficits and elevated the brain levels of monoamines in UCMS rats. UCMS-induced increase of brain cholinesterase and monoamine oxidase activities was inhibited by MJ. Also, MJ attenuated UCMS-induced decrease in antioxidant enzymes (CAT, GPx, GST, and SOD) and thiol contents in the brains of rats. UCMS-induced increase in NO level and Nrf2 immunopositive cell expression in the rat's brain was attenuated by MJ. Taken together, these findings suggest that increasing antioxidant defense molecules and monoaminergic/cholinergic neurotransmitters and decreasing the Nrf2 immunopositive cell expressions may contribute to the memory-promoting effects of MJ in rats exposed to UCMS.

Eugenia uniflora fruit extract exerts neuroprotective effect on chronic unpredictable stress-induced behavioral and neurochemical changes

The aim of the current study was to evaluate the effect of chronic administration of Eugenia uniflora fruit extract on behavioral parameters, oxidative stress markers, and acetylcholinesterase activity in an animal model of depression, which was induced by chronic unpredictable stress (CUS). Mice were divided into six groups as follows: control/vehicle (water), control/fluoxetine (20 mg/kg), control/extract (200 mg/kg), CUS/vehicle, CUS/fluoxetine (20 mg/kg), and CUS/extract (200 mg/kg). Animals of the CUS group were exposed to a series of stressors for a period of 21 days. Vehicle, fluoxetine, and hydroalcoholic extract were administered daily by gavage. Results showed that E. uniflora treatment: (a) prevented the depressant-like effect induced by CUS; (b) regulated the activity of acetylcholinesterase; (c) reduced oxidative damage to lipids and reactive oxygen species production, in the prefrontal cortex and hippocampus; and (d) prevented the reduction of glutathione peroxidase in the hippocampus of animals subjected to CUS protocol. Taken together, our findings suggested that E. uniflora extract exerts a neuroprotective effect by preventing oxidative damage and decreasing CUS-induced acetylcholinesterase activity, thus, ameliorating depressive-type behavior. PRACTICAL APPLICATIONS: E. uniflora fruit extract revealed an antidepressant-like effect and prevented the oxidative damage as well as cholinergic alterations caused by chronic stress in mice. Therefore, we believe that the results obtained in this study can be used to develop an alternative therapy for the management of depressive disorders.

Mechanisms of Panax ginseng action as an antidepressant

OBJECTIVES

Panax ginseng, a well-known traditional Chinese medicine with multiple pharmacological activities, plays a crucial role in modulating mood disorders. Several recent studies have identified an underlying role of Panax ginseng in the prevention and treatment of depression. However, the cellular and molecular mechanisms remain unclear.

MATERIALS AND METHODS

In this review, we summarized the recent progress of antidepressant effects and underlying mechanisms of Panax ginseng and its representative herbal formulae.

RESULTS

The molecular and cellular mechanisms of Panax ginseng and its herbal formulae include modulating monoamine neurotransmitter system, upregulating the expression of neurotrophic factors, regulating the function of HPA axis, and anti-inflammatory action.

CONCLUSIONS

Therefore, this review may provide theoretical bases and clinical applications for the treatment of depression by Panax ginseng and its representative herbal formulae.

High Exploratory Phenotype Rats Exposed to Environmental Stressors Present Memory Deficits Accompanied by Immune-Inflammatory/Oxidative Alterations: Relevance to the Relationship Between Temperament and Mood Disorders

Low-exploratory (LE) and high-exploratory (HE) rodents mimic human depressive and hyperthymic temperaments, respectively. Mood disorders (MD) may be developed by the exposure of these temperaments to environmental stress (ES). Psychiatric symptoms severity in MD patients is related to the magnitude of memory impairment. Thus, we aimed at studying the consequences of the exposure of LE and HE male Wistar rats, during periadolescence, to a combination of ES, namely, paradoxical sleep deprivation (PSD) and unpredictable stress (US), on anxiety-related behavior in the plus maze test, working (WM) and declarative memory (DM) performance. We also evaluated hippocampal immune-inflammatory/oxidative, as consequences of ES, and prevention of ES-induced alterations by the mood-stabilizing drugs, lithium and valproate. Medium exploratory (ME) control rats were used for comparisons with HE- and LE-control rats. We observed that HE-controls presented increased anxiolytic behavior that was significantly increased by ES exposure, whereas LE-controls presented increased anxiety-like behavior relative to ME-controls. Lithium and valproate prevented anxiolytic alterations in HE+ES rats. HE+ES- and LE+ES-rats presented WM and DM deficits. Valproate and lithium prevented WM deficits in LE-PSD+US rats. Lithium prevented DM impairment in HE+ES-rats. Hippocampal levels of reduced glutathione (GSH) increased four-fold in HE+ES-rats, being prevented by valproate and lithium. All groups of LE+ES-rats presented increased levels of GSH in relation to controls. Increments in lipid peroxidation in LE+ES- and HE+ES-rats were prevented by valproate in HE+ES-rats and by both drugs in LE+ES-rats. Nitrite levels were increased in HE+ES- and LE+ES-rats (five-fold increase), which was prevented by both drugs in LE+ES-rats. HE+ES-rats presented a two-fold increase in the inducible nitric oxide synthase (iNOS) expression that was prevented by lithium. HE+ES-rats showed increased hippocampal and plasma levels of interleukin (IL)-1β and IL-4. Indoleamine 2, 3-dioxygenase 1 (IDO1) was increased in HE+ES- and LE+ES-rats, while tryptophan 2,3-dioxygenase (TDO2) was increased only in HE+ES-rats. Altogether, our results showed that LE- and HE-rats exposed to ES present distinct anxiety-related behavior and similar memory deficits. Furthermore, HE+ES-rats presented more brain and plasma inflammatory alterations that were partially prevented by the mood-stabilizing drugs. These alterations in HE+ES-rats may possibly be related to the development of mood symptoms.

Psychological Stress and Mitochondria: A Systematic Review

OBJECTIVE

Mitochondria are multifunctional life-sustaining organelles that represent a potential intersection point between psychosocial experiences and biological stress responses. This article provides a systematic review of the effects of psychological stress on mitochondrial structure and function.

METHODS

A systematic review of the literature investigating the effects of psychological stress on mitochondrial function was conducted. The review focused on experimentally controlled studies allowing us to draw causal inference about the effect of induced psychological stress on mitochondria.

RESULTS

A total of 23 studies met the inclusion criteria. All studies involved male laboratory animals, and most demonstrated that acute and chronic stressors influenced specific facets of mitochondrial function, particularly within the brain. Nineteen studies showed significant adverse effects of psychological stress on mitochondria and four found increases in function or size after stress. In humans, only six observational studies were available, none with experimental designs, and most only measured biological markers that do not directly reflect mitochondrial function, such as mitochondrial DNA copy number.

CONCLUSONS

Overall, evidence supports the notion that acute and chronic stressors influence various aspects of mitochondrial biology, and that chronic stress exposure can lead to molecular and functional recalibrations among mitochondria. Limitations of current animal and human studies are discussed. Maladaptive mitochondrial changes that characterize this subcellular state of stress are termed mitochondrial allostatic load. Prospective studies with sensitive measures of specific mitochondrial outcomes will be needed to establish the link between psychosocial stressors, emotional states, the resulting neuroendocrine and immune processes, and mitochondrial energetics relevant to mind-body research in humans.

Ginseng: An Nonnegligible Natural Remedy for Healthy Aging

Aging is an irreversible physiological process that affects all humans. Numerous theories have been proposed to regarding the process from a Western medicine perspective; however, ancient Chinese medicine practices and theories have increasingly gained attention, particularly ginseng, a grass that has been studied for the anti-aging properties of its active constituents. This review seeks to analyze current data on ginseng and its anti-aging properties. The plant species, characteristics, and active ingredients will be introduced. The main part of this review is focused on ginseng and its active components with regards to their effects on prolonging lifespan, the regulation of multiple organ systems including cardiovascular, nervous, immune, and skin, as well as the anti-oxidant and anti-inflammatory properties. The molecular mechanisms of these properties elucidated via various studies are summarized as further evidence of the anti-aging effects of ginseng.

Impact of Chronic Stress Protocols in Learning and Memory in Rodents: Systematic Review and Meta-Analysis

The idea that maladaptive stress impairs cognitive function has been a cornerstone of decades in basic and clinical research. However, disparate findings have reinforced the need to aggregate results from multiple sources in order to confirm the validity of such statement. In this work, a systematic review and meta-analyses were performed to aggregate results from rodent studies investigating the impact of chronic stress on learning and memory. Results obtained from the included studies revealed a significant effect of stress on global cognitive performance. In addition, stressed rodents presented worse consolidation of learned memories, although no significantly differences between groups at the acquisition phase were found. Despite the methodological heterogeneity across studies, these effects were independent of the type of stress, animals’ strains or age. However, our findings suggest that stress yields a more detrimental effect on spatial navigation tests’ performance. Surprisingly, the vast majority of the selected studies in this field did not report appropriate statistics and were excluded from the quantitative analysis. We have therefore purposed a set of guidelines termed PROBE (Preferred Reporting Orientations for Behavioral Experiments) to promote an adequate reporting of behavioral experiments.

Depression mediates impaired glucose tolerance and cognitive dysfunction: A neuromodulatory role of rosiglitazone

Comorbidity of depression and diabetes is a serious risk factor worsening the complications such as cognitive function and locomotion. Treatment under this condition becomes extremely complicated. Insulin signaling and autophagy pathways are involved in modulation of learning and memory. Rosiglitazone (ROSI) ameliorate cognitive deficit associated with depression and insulin resistance. In the present study, we investigated the effect of ROSI against chronic unpredictable stress (CUS) induced depression as a risk factor for diabetes and behavioral dysfunctions. Adult male Swiss albino mice were exposed to CUS alongside ROSI (5mg/kg/day) treatment for 21days. Thereafter, animals were subjected to different behavioral studies to assess depressive like behavior, cognition and locomotion. The effect of ROSI on insulin signaling, autophagy and apoptosis were evaluated in the hippocampus. CUS resulted in depressive like behavior, cognitive impairment and hypolocomotion associated with oxidative stress, impaired glucose tolerance and hypercorticosteronemia. CUS significantly impaired hippocampal insulin signaling, membrane translocation of glucose transporter type 4 (GLUT4) as well as decreased the expression of autophagy5, autophagy7, B-cell lymphoma 2 and apoptosis inhibitory protein 2. ROSI significantly reduced depressive like behavior, postprandial blood glucose, hypercorticosteronemia, oxidative and inflammatory stress, and apoptosis in stressed mice. Moreover, ROSI treatment effectively improved hippocampal insulin signaling, GLUT4 membrane translocation and cognitive performance in depressed mice. ROSI administration might prove to be effective for neurological disorders associated with depressive like behavior and impaired glucose tolerance.

Hesperidin and Silibinin Ameliorate Aluminum-Induced Neurotoxicity: Modulation of Antioxidants and Inflammatory Cytokines Level in Mice Hippocampus

Mounting evidence suggests that long-term aluminum exposure results in severe toxic effects, including neurobehavioral and neurochemical anomalies. The present study was performed to examine the neuroprotective potential of hesperidin and silibinin against aluminum chloride (AlCl3)-induced neurotoxicity in mice. AlCl3 (100 mg/kg/day) was injected daily through oral gavage for 42 days. Concomitantly, hesperidin (50 and 100 mg/kg/day, p.o.) and silibinin (100 and 200 mg/kg/day, p.o.) was administered for 42 days in different groups. The extent of cognitive impairment was assessed by Morris water maze and novel object recognition test on the 43rd day. Neurotoxicity was assessed by measuring oxido-nitrosative stress and proinflammatory cytokines in the hippocampus of mice. Six weeks treatment with AlCl3 caused cognitive impairment as indicated by an increase in the retention latency time and reduction in the percentage of recognition index. AlCl3-treated group showed oxido-nitrosative stress as indicated by increase in the level of lipid peroxidation, nitrite and depleted reduced glutathione, catalase activity in the hippocampus. Moreover, the chronic AlCl3 administration raised the proinflammatory cytokines (interleukin-1β and tumor necrosis factor-α) level and increased acetylcholinesterase activity and reduced the BDNF content in the hippocampus of AlCl3-treated animals. However, chronic treatment with hesperidin and silibinin at higher doses significantly ameliorated the AlCl3-induced cognitive impairment and hippocampal biochemical anomalies. The present study clearly indicated that hesperidin and silibinin exert neuroprotective effects against AlCl3-induced cognitive impairment and neurochemical changes. Amelioration of cognitive impairment may be attributed to the impediment of oxido-nitrosative stress and inflammation in the hippocampus.

A critical evaluation of the activity-regulated cytoskeleton-associated protein (Arc/Arg3.1)'s putative role in regulating dendritic plasticity, cognitive processes, and mood in animal models of depression

Major depressive disorder (MDD) is primarily conceptualized as a mood disorder but cognitive dysfunction is also prevalent, and may limit the daily function of MDD patients. Current theories on MDD highlight disturbances in dendritic plasticity in its pathophysiology, which could conceivably play a role in the production of both MDD-related mood and cognitive symptoms. This paper attempts to review the accumulated knowledge on the basic biology of the activity-regulated cytoskeleton-associated protein (Arc or Arg3.1), its effects on neural plasticity, and how these may be related to mood or cognitive dysfunction in animal models of MDD. On a cellular level, Arc plays an important role in modulating dendritic spine density and remodeling. Arc also has a close, bidirectional relationship with postsynaptic glutamate neurotransmission, since it is stimulated by multiple glutamatergic receptor mechanisms but also modulates α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor internalization. The effects on AMPA receptor trafficking are likely related to Arc's ability to modulate phenomena such as long-term potentiation, long-term depression, and synaptic scaling, each of which are important for maintaining proper cognitive function. Chronic stress models of MDD in animals show suppressed Arc expression in the frontal cortex but elevation in the amygdala. Interestingly, cognitive tasks depending on the frontal cortex are generally impaired by chronic stress, while those depending on the amygdala are enhanced, and antidepressant treatments stimulate cortical Arc expression with a timeline that is reminiscent of the treatment efficacy lag observed in the clinic or in preclinical models. However, pharmacological treatments that stimulate regional Arc expression do not universally improve relevant cognitive functions, and this highlights a need to further refine our understanding of Arc on a subcellular and network level.

Urtica dioica leaves modulates muscarinic cholinergic system in the hippocampus of streptozotocin-induced diabetic mice

Diabetes mellitus is a chronic metabolic disorder and has been associated with cognitive dysfunction. In our earlier study, chronic Urtica dioica (UD) treatment significantly ameliorated diabetes induced associative and spatial memory deficit in mice. The present study was designed to explore the effect of UD leaves extract on muscarinic cholinergic system, which has long been known to be involved in cognition. Streptozotocin (STZ) (50 mg/kg, i.p., consecutively for 5 days) was used to induce diabetes followed by treatment with UD extract (50 mg/kg, oral) or rosiglitazone (5 mg/kg, oral) for 8 weeks. STZ-induced diabetic mice showed significant reduction in hippocampal muscarinic acetylcholine receptor-1 and choline acetyltransferase expressions. Chronic diabetes significantly up-regulated the protein expression of acetylcholinesterase associated with oxidative stress in hippocampus. Besides, STZ-induced diabetic mice showed hypolocomotion with up-regulation of muscarinic acetylcholine receptor-4 expression in striatum. Chronic UD treatment significantly attenuated the cholinergic dysfunction and oxidative stress in the hippocampus of diabetic mice. UD had no effect on locomotor activity and muscarinic acetylcholine receptor-4 expression in striatum. In conclusion, UD leaves extract has potential to reverse diabetes mediated alteration in muscarinic cholinergic system in hippocampus and thereby improve memory functions.