Age-related decline in central cholinergic function demonstrated with scopolamine

Lactobacillus paracasei HP7 with Portulaca oleracea Linn. Alleviates Scopolamine-Induced Cognitive Decline via Regulation of Neurotrophic Factor and Inflammation Signals in Mice

People often experience cognitive deterioration of various degrees, from early-stage mild cognitive impairment to severe cognitive decline. Cognitive deterioration is related to many diseases and studied to alleviated inflammation reaction or oxidative stress. In the present study, the levels of various memory-related proteins: brain-derived neurotrophic factor (BDNF), amyloid beta (Aβ) 42, Aβ40, interleukin-6 and tumor necrosis factor-alpha were measured. Among Lactobacillus paracasei HP7 (HP7), Portulaca oleracea Linn. (PO) and HP7 together with PO (HP7A), the HP7A group had the best effect on increasing BDNF expression and suppressing Aβ40 expression. Also, we measured the protective effect on scopolamine-induced cognitive decline in mice. In the acquisition test, the HP7A group most reliably relieved cognitive decline from days 2 to 5 of scopolamine injection. When the probe test was performed on the day 6 of scopolamine injection, the HP7A group had the shortest escape latency. Based on the results of the Morris water maze tasks, we suggest that HP7A is most useful for ameliorating cognitive decline. It is suggested that the HP7A ameliorating scopolamine-induced cognitive decline via the increase of BDNF expression and the suppression of Aβ40 expression.

Interaction of cholinergic disruption and age on cognitive flexibility in rats

Healthy aging is associated with a functional reduction of the basal forebrain (BF) system that supplies the neurochemical acetylcholine (ACh) to the cortex, and concomitant challenges to cognition. It remains unclear how aging and ACh loss interact to shape cognition in the aging brain. We used a proactive interference (PI) odor discrimination task, shown to depend on the BF in young adults, wherein rats acquired new associations that conflicted with past learning or associations that did not conflict. This manipulation allowed independent assessment of encoding alone vs. encoding in the face of interference. Adult (9.8 ± 1.3 months) or aged male Long-Evans rats (20.7 ± 0.5 months) completed the PI task with systemic administration of a muscarinic cholinergic antagonist, scopolamine, or a pharmacological control. Aged rats were less able to resolve PI than adult rats. Moreover, while scopolamine reduced efficient PI resolution in adult rats, this cholinergic antagonism had no additional effect on aged rat performance, counter to our expectation that scopolamine would further increase perseveration in the aged group. Scopolamine did not impair encoding of non-interfering associations regardless of age. These data suggest that natural aging changes the effect of cholinergic pharmacology on encoding efficiency when past learning interferes.

Adverse Effects of Anticholinergic Drugs on Cognition and Mobility: Cutoff for Impairment in a Cross-Sectional Study in Young-Old and Old-Old Adults

BACKGROUND

Drugs with anticholinergic properties are commonly prescribed in older adults despite growing evidence of their adverse outcomes. Several issues regarding these detrimental effects remain unresolved, such as the putative existence of a threshold above which anticholinergic drug consumption impairs cognitive or mobility performance.

OBJECTIVES

We aimed to investigate the number of anticholinergic drugs and the anticholinergic burden that leads to mobility or cognitive impairment and compare the effects in community-dwelling older adults in two age groups ("young-old" 55-74 vs. "old-old" ≥ 75 years).

METHODS

In a cross-sectional study, we identified drugs with anticholinergic (antimuscarinic) properties using the Anticholinergic Drug Scale. Cognition was assessed using the Mini Mental State Examination (MMSE) and the Trail Making Test (TMT-A and TMT-B), and mobility was assessed using the Timed Up and Go (TUG) test.

RESULTS

The study population consisted of 177 volunteers, 114 of whom were classed as young-old and 63 were classed as old-old adults. Despite the lack of cutoff values for impaired outcomes in young-old adults, impaired MMSE were significantly more numerous in users than in nonusers of anticholinergic drugs. In old-old adults, receiver operating characteristic (ROC) curve analysis indicated that taking a single anticholinergic drug per day was associated with impaired TMT-B completion time, TMT difference score (B-A), and TUG scores. The cutoff for anticholinergic burden was also one for these same outcomes. Based on these cutoff values, multivariate logistic regressions in old-old adults showed that the increased risk of impaired cognition and mobility was independent of confounding factors, including comorbidities. They also suggested that anticholinergic drugs would affect mobility through executive functions.

CONCLUSIONS

Drugs with anticholinergic (antimuscarinic) properties are associated with cognitive impairment in individuals as young as 55 years, and only one such drug per day, regardless of its anticholinergic burden, is associated with both impaired cognition and impaired mobility in old-old adults. Therefore, wherever possible, clinicians should avoid prescribing drugs with anticholinergic properties.

Proton pump inhibitors act with unprecedented potencies as inhibitors of the acetylcholine biosynthesizing enzyme-A plausible missing link for their association with incidence of dementia

INTRODUCTION

Several pharmacoepidemiological studies indicate that proton pump inhibitors (PPIs) significantly increase the risk of dementia. Yet, the underlying mechanism is not known. Here, we report the discovery of an unprecedented mode of action of PPIs that explains how PPIs may increase the risk of dementia.

METHODS

Advanced in silico docking analyses and detailed enzymological assessments were performed on PPIs against the core-cholinergic enzyme, choline-acetyltransferase (ChAT), responsible for biosynthesis of acetylcholine (ACh).

RESULTS

This report shows compelling evidence that PPIs act as inhibitors of ChAT, with high selectivity and unprecedented potencies that lie far below their in vivo plasma and brain concentrations.

DISCUSSION

Given that accumulating evidence points at cholinergic dysfunction as a driving force of major dementia disorders, our findings mechanistically explain how prolonged use of PPIs may increase incidence of dementia. This call for restrictions for prolonged use of PPIs in elderly, and in patients with dementia or amyotrophic lateral sclerosis.

QTC-4-MeOBnE Rescues Scopolamine-Induced Memory Deficits in Mice by Targeting Oxidative Stress, Neuronal Plasticity, and Apoptosis

Cognitive decline and memory impairment induced by disruption of cholinergic neurons and oxidative brain damage are among the earliest pathological hallmark signatures of Alzheimer's disease. Scopolamine is a postsynaptic muscarinic receptor blocker which causes impairment of cholinergic transmission resulting in cognitive deficits. Herein we investigated the effect of QTC-4-MeOBnE (1-(7-chloroquinolin-4-yl)-N-(4-methoxybenzyl)-5-methyl-1H-1,2,3-triazole-4-carboxamide) on memory impairments in mice chronically treated with scopolamine and the molecular mechanisms involved. Administration of scopolamine (1 mg/kg) for 15 days resulted in significant impairments in working and short-term memory in mice, as assessed by the novel object recognition and the Y-maze paradigms. However, both deficits were prevented if mice receiving the scopolamine were also treated with QTC-4-MeOBnE. This effect was associated with an increase in antioxidant enzymes (superoxide dismutase and catalase), a reduction in lipid peroxidation, and an increase in Nrf2 expression. Moreover, brains from QTC-4-MeOBnE treated mice had a significant decrease in acetylcholinesterase activity and glycogen synthase kinase-3β levels but an increase in brain-derived neurotrophic factor and Bcl-2 expression levels. Taken together our findings demonstrate that the beneficial effect of QTC-4-MeOBnE in a mouse model of scopolamine-induced memory impairment is mediated via the involvement of different molecular pathways including oxidative stress, neuroplasticity, neuronal vulnerability, and apoptosis. Our study provides further evidence on the promising therapeutic potential of QTC-4-MeOBnE as a multifactorial disease modifying drug in AD and related dementing disorders.

TAK-915, a phosphodiesterase 2A inhibitor, ameliorates the cognitive impairment associated with aging in rodent models

Changes in the cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) signaling are implicated in older people with dementia. Drugs that modulate the cAMP/cGMP levels in the brain might therefore provide new therapeutic options for the treatment of cognitive impairment in aging and elderly with dementia. Phosphodiesterase 2A (PDE2A), which is highly expressed in the forebrain, is one of the key phosphodiesterase enzymes that hydrolyze cAMP and cGMP. In this study, we investigated the effects of PDE2A inhibition on the cognitive functions associated with aging, such as spatial learning, episodic memory, and attention, in rats with a selective, brain penetrant PDE2A inhibitor, N-{(1S)-1-[3-fluoro-4-(trifluoromethoxy)phenyl]-2-methoxyethyl-7-methoxy-2-oxo-2,3-dihydropyrido[2,3-b]pyrazine-4(1H)-carboxamide (TAK-915). Repeated treatment with TAK-915 (3 mg/kg/day, p.o. for 4 days) significantly reduced escape latency in aged rats in the Morris water maze task compared to the vehicle treatment. In the novel object recognition task, TAK-915 (1, 3, and 10 mg/kg, p.o.) dose-dependently attenuated the non-selective muscarinic antagonist scopolamine-induced memory deficits in rats. In addition, oral administration of TAK-915 at 10 mg/kg significantly improved the attentional performance in middle-aged, poorly performing rats in the 5-choice serial reaction time task. These findings suggest that PDE2A inhibition in the brain has the potential to ameliorate the age-related cognitive decline.

Ginsenosides Rg5 and Rk1 Enriched Cultured Wild Ginseng Root Extract Bioconversion of Pediococcus pentosaceus HLJG0702: Effect on Scopolamine-Induced Memory Dysfunction in Mice

Wild ginseng is known to contain additional physiologically and pharmacologically active substances than common ginseng. The utilization of this herb can be maximized by altering its composition via tissue culture generating adventitious roots. We enriched the content of specific ginsenosides and investigated their role in ameliorating memory impairment. Cultured wild ginseng root was subjected to extraction, steaming, and fermentation using Pediococcus pentosaceus HLJG0702 to enhance the levels of ginsenosides Rg5 /Rk1. The analysis of product, HLJG0701, confirmed target ginsenosides. We analyzed the inhibitory effect of ginsenoside Rg5/Rk1, HLJG0701 and the raw material on acetylcholinesterase. Further, we performed Morris water maze, Y-maze, and passive avoidance tasks with mice exhibiting memory deficit induced by scopolamine, and we analyzed the concentrations of acetylcholinesterase and acetylcholine in their brains. Studies showed that the levels of ginsenosides Rg5 /Rk1, not found in the raw material, were enhanced in HLJG0701. Ginsenosides and HLJG0701 significantly inhibited acetylcholinesterase unlike the raw material. In all behavioral tasks, HLJG0701 showed memory improvement. It reduced acetylcholinesterase, whereas, it preserved acetylcholine in brain. In conclusion, cultured wild ginseng root extract fermented by P. pentosaceus HLJG0702 contains the distinctive ginsenosides Rg5/Rk1, which may ameliorate memory impairment via inhibition of acetylcholinesterase resulting in increased acetylcholine levels in the brain.

Aqueous extracts from asparagus stems prevent memory impairments in scopolamine-treated mice

Aqueous extracts fromAsparagus officinalisL. reversed scopolamine-induced cognitive impairments by increasing acetylcholine and expression of BDNF and CREB.

Anti-inflammaging effects of Lactobacillus brevis OW38 in aged mice

In the present study, lactic acid bacteria (LAB) strains were collected from kimchi and were screened to isolate strains that inhibit lipopolysaccharide (LPS) production by Escherichia coli and p16 expression and nuclear factor-kappa B (NF-κB) activation in LPS-stimulated macrophages. Oral administration of Lactobacillus brevis OW38 (1×109 cfu/mouse) to aged mice (male, 18 months old) for 8 weeks reduced the LPS level in colon fluid and blood. In addition, OW38 treatment also reduced the ratio of Firmicutes or Proteobacteria to Bacteroidetes, which was significantly higher in aged mice than in young mice. Treatment with OW38 in aged mice inhibited the expression of inflammatory markers, such as myeloperoxidase, tumour necrosis factor (TNF), and interleukin (IL)-1β, and inhibited NF-κB activation. Furthermore, it induced the expression of colonic tight junction proteins zonula occludens-1, occludin, and claudin-1. OW38 treatment also suppressed the expression of senescence markers p16, p53, and SAMHD1 in the colon and the hippocampus of aged mice. In addition, it significantly restored spontaneous alternation as well as the expression of brain-derived neurotrophic factor and doublecortin in aged mice compared to that in young mice (P<0.05). Based on these findings, we conclude that OW38 treatment may ameliorate aging-associated colitis and memory impairment by inhibiting gut microbiota LPS production, NF-κB activation, and p16 expression.

Alzheimer's Disease, Acetylcholine and Oestrogen

Common types of dementia occurring in old age are associated with the loss of cholinergic activity from basal forebrain neurons projecting to the cerebral cortex. In Alzheimer's disease this loss correlates with cognitive decline, and in dementia with Lewy bodies with neuropsychiatric features such a hallucinations. New therapies aimed at restoring the levels of acetylcholine, such as the cholinesterase inhibitors tacrine or donepezil, provide some symptomatic benefit and may also be protective. Similar symptomatic and protective effects of oestrogen may operate through stimulation of the affected cholinergic neurons. These neurons have oestrogen receptors and, in animal models, oestrogen elevates cortical cholinergic activity. Cholinergic control of vasodilation is also affected by oestrogen. Declining oestrogen in postmenopausal women is thus likely to contribute to age-related cognitive decline and increased risk of Alzheimer's via cholinergic mechanisms. In addition to accumulating evidence of the protective effect of oestrogen in Alzheimer's, there is already a report that oestrogen replacement therapy enhances the response of female patients to cholinergic medication (eg, tacrine).

WY14643 Attenuates the Scopolamine-Induced Memory Impairments in Mice

WY14643 is a selective agonist of peroxisome proliferator-activated receptor-α (PPAR-α) with neuroprotective and neurotrophic effects. The aim of this study was to evaluate the effects of WY14643 on cognitive impairments induced by scopolamine, a muscarinic acetylcholine receptor antagonist. We conducted different behavior tests including the Y-maze, Morris water maze, and passive avoidance test to measure the cognitive functions of C57BL/6J mice after scopolamine and WY14643 treatment. It was found that WY14643 injection significantly attenuated the scopolamine-induced cognitive impairments in these behavioral tests. Moreover, WY14643 treatment significantly enhanced the expression of brain-derived neurotrophic factor (BDNF) signaling cascade in the hippocampus. The usage of both PPAR-α inhibitor GW6471 and BDNF system inhibitor K252a fully prevented the memory-enhancing effects of WY14643. Therefore, these findings suggest that WY14643 could improve the scopolamine-induced memory impairments, and these effects are mediated by the activation of PPAR-α and BDNF system, thereby exhibiting a cognition-enhancing potential.

Lactobacillus pentosus var. plantarum C29 increases the protective effect of soybean against scopolamine-induced memory impairment in mice

Biological activities of soybean saponins are dependent on their metabolism by gut microbiota, which generate absorbable bioactive metabolites. Therefore, to enhance the pharmacological effect of soybean, we fermented defatted soybean powder (SP) with Lactobacillus pentosus var. plantarum C29 and measured its protective effect against scopolamine-induced memory impairment in mice using the passive avoidance, Y-maze and Morris water maze tasks. Fermentation increased soyasapogenol B, genistein and daidzein content of soybean and enhanced the protective effect of soybean against scopolamine-induced memory impairment. Additionally, compared with the exthanol extract of soybean, fermented SP (FSP) increased the expression of brain-derived neurotrophic factor (BDNF) in the hippocampi of scopolamine-treated mice. Furthermore, FSP inhibited acetylcholinesterase (AChE) activity in vitro and ex vivo. These findings suggest that C29 fermentation might increase the ameliorating effect of soybean against memory impairments by inhibiting AChE activity and increasing BDNF expression.

Soyasaponins Ab and Bb prevent scopolamine-induced memory impairment in mice without the inhibition of acetylcholinesterase

Soy (Glycine max, family Leguminosae), which contains isoflavones and saponins as main constituents, is known to exhibit memory-enhancing effects. Therefore, to investigate the role of soyasaponins in memory impairments, we isolated soyasaponins Ab (SA) and Bb (SB) from soybean and measured their protective effects against scopolamine-induced memory impairment in mice. SA and SB significantly prevented scopolamine-induced memory impairment in passive avoidance and Y-maze tasks. Compared to SA, SB rescued memory impairment more potently. Treatment with SB (10 mg/kg, p.o.) protected memory impairment in passive avoidance and Y-maze tasks to 97% (F = 68.10, P < 0.05) and 78% (F = 35.57, P < 0.05) of untreated normal control level, respectively. SA and SB (10 mg/kg) also rescued scopolamine-induced memory impairment in Morris water maze task (F = 14.51, P < 0.05). In addition, soyasaponins preserved brain-derived neurotrophic factor (BNDF) expression (F = 33.69, P < 0.05) and cAMP response element-binding (CREB) protein phosphorylation (F = 91.62, P < 0.05) in the hippocampus of scopolamine-treated mice. However, SA and SB did not inhibit acetylcholinesterase in vitro and ex vivo. On the basis of these findings, we suggest that soybean, particularly soyasaponins, may protect memory impairment by increasing BDNF expression and CREB phosphorylation.

Effects of fermented ginseng on memory impairment and β-amyloid reduction in Alzheimer's disease experimental models

This study examined the effect of fermented ginseng (FG) on memory impairment and β-amyloid (Aβ) reduction in models of Alzheimer’s disease (AD) in vitro and in vivo. FG extract was prepared by steaming and fermenting ginseng. In vitro assessment measured soluble Aβ42 levels in HeLa cells, which stably express the Swedish mutant form of amyloid precursor protein. After 8 h incubation with the FG extract, the level of soluble Aβ42 was reduced. For behavioral assessments, the passive avoidance test was used for the scopolamine-injected ICR mouse model, and the Morris water maze was used for a transgenic (TG) mouse model, which exhibits impaired memory function and increased Aβ42 level in the brain. FG extract was treated for 2 wk or 4 mo on ICR and TG mice, respectively. FG extract treatment resulted in a significant recovery of memory function in both animal models. Brain soluble Aβ42 levels measured from the cerebral cortex of TG mice were significantly reduced by the FG extract treatment. These findings extract was prepared by steaming and fermenting ginseng. of Aβ42 protein, which results in enhanced behavioral memory function, thus, suggesting that FG extract may be an effective preventive or treatment for AD.

Ginsenosides Rg5 and Rh3 protect scopolamine-induced memory deficits in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Panax ginseng (family Araliaceae) is traditionally used as a remedy for cancer, inflammation, stress and aging.

AIM OF STUDY

To explore whether ginsenosides Rg5 and Rh3, the main constituents of heat-processed ginseng (the root of Panax ginseng), could protect memory deficit.

MATERIALS AND METHODS

We isolated ginsenosides Rh3 and Rg5 from heated-processed ginseng treated with and without human feces, respectively. Then we investigated their protective effects on memory impairment using the passive avoidance, Y-maze and Morris water maze tasks in mice. Memory deficit was induced in mice by the intraperitoneal injection of scopolamine.

RESULTS

Ginsenosides Rg5 or Rh3 increased the latency time reduced by scopolamine in passive avoidance test. Treatment with ginsenoside Rg5 or Rh3 significantly reversed the lowered spontaneous alteration induced by scopolamine in Y-maze task. Ginsenoisde Rg5 or Rh3 (10 mg/kg) significantly shortened the escape latencies prolonged by treatment with scopolamine on the last day of training trial sessions in Morris water maze task. Furthermore, ginsenosides Rg5 and Rh3 inhibited acetylcholinesterase activity in a dose-dependent manner, with IC50 values of 18.4 and 10.2 μM, respectively. The inhibitory potency of ginsenoside Rh3 is comparable with that of donepezil (IC50=9.9 μM). These ginsenosides also reversed hippocampal brain-derived neurotrophic factor (BDNF) expression and cAMP response element-binding protein (CREB) phosphorylation reduced by scopolamine. Of them, ginsenoside Rh3 more potently protected memory deficit.

CONCLUSIONS

Ginsenoside Rg5 and its metabolite ginsenoside Rh3 may protect memory deficit by inhibiting AChE activity and increasing BDNF expression and CREB activation.

Lancemaside A isolated from Codonopsis lanceolata and its metabolite echinocystic acid ameliorate scopolamine-induced memory and learning deficits in mice

The rhizome of Codonopsis lanceolata (family Campanulaceae), which contains lancemaside A as a main constituent, has been used as herbal medicine to treat inflammation, insomnia, and hypomnesia. Lancemaside A and echinocystic acid, which is its metabolite by intestinal microflora, potently inhibited acetylcholinesterase activity in a dose-dependent manner, with IC₅₀ value 13.6 μM and 12.2 μM, respectively. Its inhibitory potency is comparable with that of donepezil (IC₅₀=10.9 μM). Lancemaside A and echinocystic acid significantly reversed scopolamine-induced memory and learning deficits on passive avoidance task. Lancemaside A orally administered 5h before treatment with scopolamine reversed scopolamine-induced memory and learning deficits more potently than one orally administered 1h before. Echinocystic acid more potently reversed it than lancemaside A. Lancemaside A and echinocystic acid significantly reversed scopolamine-induced memory and learning deficits on the Y-maze and Morris water maze tasks. Lancemaside A and echinocystic acid also increased the expression of brain-derived neurotrophic factor (BDNF) and phosphorylated cAMP response element binding protein (p-CREB). Based on these findings, orally administered lancemaside A may be metabolized to echinocystic acid, which may be absorbed into the blood and ameliorate memory and learning deficits by inhibiting AChE activity and inducing BDNF and p-CREB expressions.

Lactobacillus pentosus var. plantarum C29 protects scopolamine-induced memory deficit in mice

AIMS

In the preliminary study, kimchi, a traditional food fermented with Chinese cabbage, protected scopolamine-induced mouse memory deficit in passive avoidance test. Therefore, we screened protective ingredients, particularly lactic acid bacteria, from Chinese cabbage kimchi against scopolamine-induced memory deficit in mice.

METHODS AND RESULTS

Lactic acid bacteria, isolated from Chinese cabbage kimchi, were identified by 16S rDNA sequence analysis, G+C content and cellular fatty acid composition and sugar fermentation test. Memory deficit was induced in mice by intraperitoneally injecting with scopolamine. Kimchi, particularly its supernatant, protected scopolamine-induced memory deficit in mice in passive avoidance test. Of kimchi ingredients, a lactic acid bacterium, strain C29, potently protected scopolamine-induced memory deficit in mice. C29 was a gram-positive, catalase-negative, anaerobic and non-motile rod. Its pylogenetic property was near to Lactobacillus pentosus (99%) and Lact. plantarum (99%). However, C29 fermented inulin and L-rhamnose and grew in pH 3 and at 45°C in contrast with Lact. pentosus and Lact. plantarum. Therefore, it named to be Lact pentosus var. plantarum C29. The strain C29 protected scopolamine-induced memory deficit in Y-maze and Morris water maze tests. Furthermore, C29 increased hippocampal BDNF and p-CREB expressions, which were reduced by scopolamine.

CONCLUSION

Lactobacillus pentosus var. plantarum C29 may protect memory deficit by inducing BDNF and p-CREB expressions.

SIGNIFICANCE AND IMPACT OF THE STUDY

Lactic acid bacteria, such as Lact pentosus var. plantarum C29, may prevent memory deficit and its contained fermented foods may be beneficial for dementia.

Pharmacological models in Alzheimer's disease research

Wider use of pharmacological models would facilitate the development of new drugs for Alzheimer's disease (AD), The two main models currently used are based on the cholinergic and glutamatergic hypotheses of AD, Although they lead to some of the attention and memory impairment observed in AD, they do not fully reproduce the AD pattern. The few studies that used a combination modeling approach, ie, the simultaneous administration of several drugs with the aim of impairing several neurotransmitters or different aspects of a single system, have reported no or marginal cumulative effect. On the basis of current understanding of glutamate and acetylcholine involvement in AD pathophysiology, we suggest that models using selective muscarinic-1 (M(1)) receptor blockers would better mimic the status of the cholinergic system in AD, This kind of model might be suitable for the assessment of drugs that do not act directly on the cholinergic system.

The greater sensitivity of elderly APOE ε4 carriers to anticholinergic medications is independent of cerebrovascular disease risk

BACKGROUND

Recent studies found use of anticholinergic medications to be associated with greater performance decrements in older persons who carry an ε4 allele of the apolipoprotein E (APOE) gene than in those carrying only ε2 or ε3 alleles.

OBJECTIVES

The present study examined whether the apparently greater behavioral toxicity of anticholinergic drugs in ε4 carriers may result from an increased risk of cerebrovascular disease, which is more common in ε4 carriers.

METHODS

Cross-sectional data were available from 240 elderly community volunteers who had participated in 2 different studies of the cognitive and motor effects of normal aging. As part of these studies, information was gathered on subjects' use of anticholinergic medications (based on an inventory of medications taken within 24 hours of testing), risk of cerebrovascular disease (Framingham Stroke Risk Profile), and APOE genotype. Performance data were also available from measures of general cognitive status (Mini-Mental State Examination), executive function (Trail Making Test), mood (Geriatric Depression Scale), sleep (Pittsburgh Sleep Quality Index), and walking speed. Logistic and linear regression models were used to examine how outcomes differed between genotypes and drug use, independent of the risk of cerebrovascular disease.

RESULTS

In persons with a non-ε4 genotype, anticholinergic medication use did not significantly affect any of the behavioral measures. By contrast, among ε4 carriers, those taking anticholinergic drugs performed significantly worse than did those not taking such drugs on tests of general cognitive status, executive function, mood, and sleep. Adjusting for participants' stroke risk had a minimal effect on these results.

CONCLUSIONS

Anticholinergic medication use was associated with poorer performance on measures of cognition, sleep, and mood only in older persons who carried 1 or more ε4 alleles of the APOE gene; this effect did not appear to be the result of an increased risk of cerebrovascular disease.

Additive effects of a cholinesterase inhibitor and a histamine inverse agonist on scopolamine deficits in humans

RATIONALE

Enhancement of histaminergic neurotransmission or histaminergic plus cholinergic neurotransmission may represent novel strategies for improving cognition in Alzheimer's disease.

OBJECTIVE

To evaluate the effects of a novel histamine H3 receptor inverse agonist (MK-3134), an acetylcholinesterase inhibitor (donepezil), and their combination in attenuating the cognitive impairment associated with scopolamine.

METHODS

Thirty-one subjects were randomized, and 28 completed this double-blind, placebo-controlled, five-period crossover study. Cognition was assessed using the Groton Maze Learning Task (GMLT) as the primary outcome measure. The two primary hypotheses were that donepezil 10 mg and MK-3134 25 mg, respectively, would attenuate scopolamine (0.5 mg)-induced impairment as measured by the GMLT over the first 12 h after scopolamine administration (AUC(1-12)  (h)). A secondary hypothesis was that the combination of donepezil and MK-3134 would attenuate scopolamine-induced cognitive impairment to a greater extent than either agent alone as measured by the GMLT AUC(1-12 h).

RESULTS

The primary and secondary hypotheses were not met. Upon examining the time course of the scopolamine effects (an exploratory objective), peak effects were generally observed around 2 h after scopolamine administration. Administration of MK-3134 or donepezil improved performance on the GMLT at the 2-h time point, rather than AUC(1-12 h), compared with scopolamine alone. Moreover, it appeared that the combination of MK-3134 and donepezil blunted the scopolamine effect to a greater extent than either drug alone.

CONCLUSIONS

Exploratory analyses provide evidence for cognitive improvement through inverse agonism of the H3 histamine receptor and for cooperation between human cholinergic and histaminergic neurotransmitter systems. (ClinicalTrials.gov trial registration number: NCT01181310).

Cognitive enhancement following acute losartan in normotensive young adults

RATIONALE

Losartan, an angiotensin II receptor antagonist (AIIA), is an antihypertensive that has previously been suggested to have cognitive-enhancing potential for older adults. The objective indices for such effects are equivocal, however, and if these drugs do offer dual advantages of hypertension control plus cognitive-enhancing potential, there exists a clear need to establish this directly.

OBJECTIVES

This work examines the potential of losartan administered as a single dose to healthy young adults to improve cognitive performance alone or to reverse scopolamine-induced cognitive decrements.

METHODS

In two placebo-controlled, double-blind studies, participants completed a cognitive test battery once before and once after drug absorption. In experiment 1, participants were randomly allocated to receive placebo, losartan 50 mg or losartan 100 mg. In experiment 2, participants were randomly allocated to one of four treatment groups: placebo/placebo, placebo/scopolamine, losartan/scopolamine and losartan/placebo (50 mg losartan p.o. and 1.2 mg scopolamine hydrochloride p.o.).

RESULTS

Losartan 50 mg improved performance on a task of prospective memory when administered alone and reversed the detrimental effects of scopolamine both in a standard lexical decision paradigm (p < 0.01) and when the task incorporated a prospective memory component (p < 0.008).

CONCLUSIONS

The findings highlight a cognitive-enhancing potential for losartan on compromised cognitive systems and emphasise the potential of AIIAs to produce benefits over and above hypertension control.

Gypenoside TN-2 ameliorates scopolamine-induced learning deficit in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Gynostemma pentaphyllum (Thunb.) Makino (GP, family Cucurbitaceae), which contains dammarane saponins as its main constituents, is used in China, Japan, and Korea as a traditional medicine to treat cancer, obesity, arteriosclerosis, asthma and senility.

AIM OF THE STUDY

To investigate the memory-enhancing effects of GP, Gypenoside TN-2 (TN-2) was isolated by activity-guided fractionation and administered to scopolamine-induced memory-deficient mice.

MATERIALS AND METHODS

The memory-enhancing effects of TN-2 were evaluated using passive avoidance, Y-maze, and Morris water maze tests, and the protein expressions of brain-derived neurotrophic factor (BDNF), cAMP element binding protein (CREB), and p-CREB were determined by immunoblotting.

RESULTS

TN-2 inhibited memory and learning deficits in scopolamine treated mice in the passive avoidance test. TN-2 (10, 20, and 40 mg/kg, p.o.) significantly inhibited memory and learning deficits in the passive avoidance test by 40%, 96% and 78%, respectively, and exhibited significant memory-enhancing effects on the Y-maze test and the Morris water maze test. TN-2 also markedly increased BNDF expression and activated the transcription factor CREB in the hippocampi of scopolamine-treated mice.

CONCLUSIONS

TN-2 may ameliorate memory and learning deficits by activating the CREB-BDNF pathway.

Magnetoencephalography as a putative biomarker for Alzheimer's disease

Alzheimer's Disease (AD) is the most common dementia in the elderly and is estimated to affect tens of millions of people worldwide. AD is believed to have a prodromal stage lasting ten or more years. While amyloid deposits, tau filaments, and loss of brain cells are characteristics of the disease, the loss of dendritic spines and of synapses predate such changes. Popular preclinical detection strategies mainly involve cerebrospinal fluid biomarkers, magnetic resonance imaging, metabolic PET scans, and amyloid imaging. One strategy missing from this list involves neurophysiological measures, which might be more sensitive to detect alterations in brain function. The Magnetoencephalography International Consortium of Alzheimer's Disease arose out of the need to advance the use of Magnetoencephalography (MEG), as a tool in AD and pre-AD research. This paper presents a framework for using MEG in dementia research, and for short-term research priorities.

Cognitive slowing associated with elevated serum anticholinergic activity in older individuals is decreased by caffeine use

OBJECTIVES

This study examined whether some of the age-associated decrements in basic cognitive resources (information-processing speed and working memory) result from anticholinergic medication use (as measured by serum anticholinergic activity [SAA]) and whether such decrements are lessened by caffeine.

DESIGN

Cross-sectional observational study.

SETTING

University medical center.

PARTICIPANTS

One hundred fifty-two normal-elderly community volunteers.

MEASUREMENTS

Two tests each of information-processing speed and of working memory were administered, and blood samples were drawn before and after cognitive testing to determine serum levels of anticholinergic activity and of paraxanthine-a caffeine metabolite.

RESULTS

Elevated SAA was associated with a significant but modest slowing in information-processing time but only in those individuals who had low levels of serum paraxanthine. SAA did not correlate with performance on tests of working memory.

CONCLUSIONS

These results suggest that anticholinergic medications are a relatively minor contributor to the decrements in basic processing resources commonly found in studies of normal aging.

Retrograde facilitation of verbal memory by trihexyphenidyl in healthy elderly with and without the APOE epsilon4 allele

Retrograde facilitation (RF) of information learned prior to acute oral administration of trihexyphenidyl, a preferential muscarinic M1 receptor antagonist which impairs new learning, was studied in 24 healthy elderly subjects. The relationship between the RF induced by this anticholinergic drug and the APOE epsilon4 allele was also examined. Acute adverse performance effects of trihexyphenidyl (1- and 2mg) were determined using the Buschke Selective Reminding Test administered pre-drug and at 1, 2.5, and 5h post-drug. Recall of pre-drug words at the end of the fifth hour neuropsychological assessment (end-of-session recall) was of primary interest. Words studied before drug administration were better recalled following 2mg trihexyphenidyl compared to placebo, and this RF effect was not affected by the APOE epsilon4 allele. Better recall of pre-drug words following 2-mg trihexyphenidyl was associated with a greater amnestic effect of this dose. Our findings demonstrated that RF induced by trihexyphenidyl was related to anterograde amnestic effects of the drug and resulted in part from drug-induced reduction of retroactive interference.

Cholinergic modulation of preattentive auditory processing in aging

Auditory event-related potential (ERP) components P50 and N100 are thought to index preattentive auditory processing underlying stimulus detection, whereas a subsequent component termed mismatch negativity (MMN) has been proposed to reflect comparison of incoming stimuli to a short-lived sensory memory trace of preceding sounds. Existing evidence suggests impairment of preattentive auditory processing in aging, which appears to be accompanied by decline of cholinergic activity. Previous studies indicate that scopolamine, which is a centrally acting muscarinic receptor antagonist, modulates preattentive auditory processing in young subjects. It has remained elusive, however, to which extent scopolamine affects preattentive auditory processing in aged subjects. We measured auditory responses simultaneously with electroencephalogram (EEG) and magnetoencephalogram (MEG) from nine non-demented elderly subjects after intravenous injection of scopolamine or glycopyrrolate, the latter being a peripherally acting cholinergic antagonist, using a double blind protocol. Scopolamine significantly delayed electric P50, both electric and magnetic N100 responses, whereas subsequent MMN and P200 responses were not altered by scopolamine. Our results indicate that the cholinergic system modulates auditory processing underlying stimulus detection in aging. In addition, auditory evoked responses appear to have different age-related sensitivity to cholinergic modulation. The combined MEG/EEG measurements using particularly auditory N100 response might offer an objective tool to monitor cholinergic activity in aging and Alzheimer's disease (AD).

Effects of scopolamine challenge on regional cerebral blood volume. A pharmacological model to validate the use of contrast enhanced magnetic resonance imaging to assess cerebral blood volume in a canine model of aging

Cognitive impairment resulting from disruption of cholinergic function may occur through modulation of cerebrovascular volume (CBV). In the present study, dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) was used to examine cerebrovascular volume in young and old dogs during baseline and after administration of a cholinergic antagonist (scopolamine). In the first study, 24 animals (2-15 years of age) were given a baseline scan followed by a second scan after scopolamine administration (30 microg/kg). Gray matter rCBV was significantly higher than white matter rCBV during baseline and scopolamine administration. In the second study a subset of 7 dogs (4 young and 3 old) received scopolamine before anesthesia was induced for a second DSC-MRI scan. Consistent with the first study, gray matter rCBV was significantly higher than white matter rCBV. Scopolamine administered before anesthesia however, resulted in higher rCBV values compared to baseline in cerebral gray matter. Additionally, rCBVs were higher in young dogs at baseline in gray and white matter and marginally higher in gray matter when scopolamine was administered before anesthesia. These results indicate that in the dog, rCBV varies with brain compartment, decreases with age, and that DSC-MRI provides a measure of cerebrovascular function which may be related to age-dependent changes in cognition, brain structure, and neuropathology.

Further evidence for the cholinergic hypothesis of aging and dementia from the canine model of aging

Memory decline in human aging and dementia is linked to dysfunction of the cholinergic system. Aging dogs demonstrate cognitive impairments and neuropathology that models human aging and dementia. This paper reviews recent evidence suggesting cholinergic involvement in canine cognitive aging based on studies with the anti-cholinergic drug, scopolamine, and a novel acetylcholinesterase inhibitor, phenserine. In particular, we examine: (1) the cognitive specificity of scopolamine's impairment in dogs, (2) the effect of age on scopolamine impairment and (3) the effect of phenserine on cognitive performance in dogs. Our findings indicate that working memory performance is disrupted by scopolamine at doses that do not disrupt non-cognitive behavior or long-term, semantic-like, memory, as indicated by performance of previously learned discriminations. This pattern of deficits is also seen in human and canine aging. We demonstrate that aged dogs are more sensitive to the impairing effects of scopolamine than young dogs, suggesting a decrease in cholinergic tone with increasing age. Dogs receiving phenserine demonstrate improved learning and memory compared to placebo controls. Our findings suggest that cholinergic decline could result in memory impairment, but that the memory impairment may be secondary to deficits in attention and/or encoding of new information. Together, these results suggest that the canine cholinergic system declines with age and that the aged dog is a unique model for screening therapeutics and for examining the relationship between amyloid pathology and cholinergic dysfunction in age-dependent cognitive decline.

Increased anticholinergic challenge-induced memory impairment associated with the APOE-epsilon4 allele in the elderly: a controlled pilot study

The degree to which elderly adults experience cognitive impairments from centrally acting anticholinergic drugs is variable, but the cause of this variability is unknown. The present study examined the epsilon4 allele as a possible modulator of the effects of trihexyphenidyl hydrochloride (Artane( trade mark )), an anticholinergic drug, on memory functioning. Of the 24 cognitively intact, elderly participants (age range 62-76), 12 who possessed the epsilon4 allele, participated in a double-blind, randomized, placebo-controlled, crossover, three-way study. All participants were tested after receiving a single oral dose of trihexyphenidyl (1 or 2 mg) or placebo, with a 7-day washout period between sessions. Memory and psychomotor tests were administered at baseline, and at 1, 2.5, and 5 h post-treatment. Results showed that participants with the epsilon4 allele demonstrated significant impairments in delayed recall after both 1 and 2 mg doses of trihexyphenidyl while the non-epsilon4 group did not. Additionally, while acute administration of the 2 mg dose significantly impaired total recall in both epsilon4 and non-epsilon4 carriers, the epsilon4 carriers showed a more persistent impairment. These findings held when participants with the epsilon2 allele were excluded from the analyses. The epsilon4 groups did not differ with respect to psychomotor performance or plasma drug levels. These results provide evidence suggesting that the epsilon4 allele plays a significant role in increasing cognitive sensitivity to trihexyphenidyl and that a temporal component of memory consolidation may be especially vulnerable. A larger study is warranted to confirm these preliminary findings.

Human models as tools in the development of psychotropic drugs

Despite the growing means devoted to research and development (R α D) and refinements in the preclinical stages, the efficiency of central nervous system (CMS) drug development is disappointing. Many drugs reach patient studies with an erroneous therapeutic indication andlor in incorrect doses. Apart from the first clinical studies, which are conducted in healthy volunteers and focus only on safety, iolerability, and pharmacokinetics, drug development mostly relies on patient studies. Psychiatric disorders are characterized by heterogeneity and a high rate of comorbidity. It is becoming increasingly difficult to recruit patients for clinical trials and there are many confounding factors in this population, for example, those related to treatments. In order to keep patient exposure and financial expenditure to a minimum, it is important to avoid ill-designed and inconclusive studies. This risk could be minimized by gathering pharmacodynamic data earlier in development and considering that the goal of a phase 1 plan is to reach patient studies with clear ideas about the compound's pharmacodynamic profile, its efficacy in the putative indication (proof of concept), and pharmacokinetic/pharmacodynamic relationships, in addition to safety, tolerability, and pharmacokinetics. Human models in healthy volunteers may be useful tools for this purpose, but their use necessitates a global adaptation of the phase scheme, favoring pharmacodynamic assessments without neglecting safety. We are engaged in an R α D program aimed to adapt existing models and develop new paradigms suitable for early proof of concept substantiation.

Aging and cholinergic modulation of the transient magnetic 40-Hz auditory response

Cholinergic blockade by scopolamine, a central muscarinic receptor antagonist, may produce transient memory impairment in healthy subjects, and it has been used as a neurochemical model of cognitive degeneration in aged individuals. To observe the muscarinic modulation of memory and cortical auditory processing, nine cognitively intact elderly subjects (59-80 years) were studied using neuropsychological tests and 122-channel magnetoencephalography (MEG) after an administration of scopolamine hydrobromide (0.3 mg, i.v.) or glycopyrrolate (0.2 mg, i.v.), a peripheral muscarinic antagonist. A double-blind randomized crossover design was used in two sessions separated by at least 1 week. Scopolamine, but not glycopyrrolate, produced a transient impairment of verbal memory performance in the elderly subjects. MEG indicated that the auditory-evoked 40-Hz magnetic response was significantly larger after scopolamine than after glycopyrrolate administration. Furthermore, reanalysis of our earlier results in younger subjects (20-31 years), basically supporting the present MEG findings, tentatively suggests that the scopolamine effects on the 40-Hz response may be slightly pronounced with aging. In sum, the transient magnetic 40-Hz auditory response may be useful in studies on brain cholinergic deficits in elderly subjects.

Non-serotonergic pharmacological profiles and associated cognitive effects of serotonin reuptake inhibitors

The current study was carried out to investigate the cognitive effects of two serotonin reuptake inhibitors (SSRIs), sertraline and paroxetine, with special reference to differences in their affinity for other neurotransmitter systems, i.e. anticholinergic activity of paroxetine and putative dopamine reuptake activity of sertraline. The study was conducted according to a double-blind, three-way cross-over design. During three treatment periods of 2 weeks, 24 healthy middle-aged (aged 30-50 years) subjects of both sexes received sertraline (50 mg on days 1-7, 100 mg on days 8-14), paroxetine (20 mg on days 1-7, 40 mg on days 8-14) and placebo. Paroxetine specifically impaired delayed recall in a word learning test at a dose of 20 and 40 mg. Sertraline did not affect word learning but improved performance on a verbal fluency task at a dose of 50 and 100 mg. Neither drug affected performance on a short-term memory scanning task. These subtle but significant changes in cognitive performance can be explained by subtle differences in pharmacological profiles of these SSRIs. The additional anticholinergic effects of paroxetine could account for its induction of long-term memory impairment. Similarly, the additional dopaminergic effects of sertraline could account for its induction of slightly improved verbal fluency. The impairing and facilitating cognitive effects of paroxetine and sertraline, respectively, may be more pronounced in the elderly depressed patient.

Effect of normal aging upon interhemispheric EEG coherence: analysis during rest and photic stimulation

The present study was conducted to examine and compare interhemispheric EEG coherence at rest and during photic stimulation (PS; 5, 10 and 15 Hz) in 30 younger subjects aged 22.1 +/- 2.2 (mean +/- S.D.) and 25 elderly subjects aged 56.8 +/- 4.9. The elderly subjects had significantly lower coherence in the resting EEG for the delta, theta, alpha-3, beta-1 and beta-2 frequency bands. In contrast, EEG analysis during PS showed that elderly subjects had significantly higher coherence in the frequency corresponding to PS at 15 Hz. In addition, when we examined the changes in coherence from the resting state to the stimulus condition (i.e., coherence reactivity), elderly subjects had significantly higher coherence reactivity to PS at 15 Hz. These findings suggest a low interhemispheric functional connectivity in elderly subjects under non stimulus conditions and a high connectivity during photic stimulus.

Effects of scopolamine on interhemispheric EEG coherence in healthy subjects: analysis during rest and photic stimulation

The present study of coherence analysis, in 16 healthy male volunteers, aged 24-31 years, showed that the administration of 0.25 mg of scopolamine significantly reduced interhemispheric coherence in the delta and beta-1 bands in the resting state. Scopolamine also caused a significant increase both in EEG coherence during PS and in PS-related coherence reactivity in the beta band. In addition, this compound significantly reduced total WMS scores. These findings suggest that, in addition to causing cognitive impairments, central cholinergic dysfunction can alter interhemispheric functional connectivity under both nonstimulus and stimulus conditions.

The effect of rivastigmine on sleep in elderly healthy subjects

Previous research has shown that acetylcholinesterase inhibitors may affect REM sleep, however, results are inconclusive. From the present findings it is concluded that the effects of rivastigmine, a reversible acetycholinesterase inhibitor, on REM sleep are more pronounced in the elderly where we found REM latency to be significantly reduced. This may be explained by better bioavailability and/or by reduced stability of the circadian rhythmicity in elderly individuals. Because rivastigmine is used in the treatment of Alzheimer's disease, further research investigating the relationship between the REM enhancing properties of rivastigmine and cognitive functioning seems promising.

The absence of effect of glucose on memory is associated with low susceptibility to the amnestic effects of scopolamine in a strain of mice

In this series of experiments, we examined the ability of post-training glucose injections to improve memory of the Balb/cAnNCrlBR strain of mice for a bar-pressing task. We could not replicate this effect which has been demonstrated in many other strains of mice including Balb/cbyJ, a related strain. We found that the Balb/cAnNCrlBR strain of mice is also much less sensitive to the disrupting effects produced by pre- or post-training injections of the competitive cholinergic antagonist scopolamine. This strain also shows altered glucoregulation compared to the Balb/cbyJ strain. The absence of glucose effects on memory in Balb/cAnNCrlBR mice appears to be associated with decreased sensitivity to cholinergic antagonists. These results can be contrasted with previous ones obtained in a related strain, the Balb/cbyJ, in which glucose was shown to improve memory while scopolamine could easily disrupt memory processes. Taken together, these data provide additional indirect support for the hypothesis that glucose improvement of memory is closely linked to a functional interaction with central cholinergic systems. The comparison of these two strains could be the basis for a useful animal model to investigate the relationship between age-related changes in memory and central cholinergic function.