Effects of long-term Donepezil therapy on rCBF of Alzheimer's patients

Brain perfusion effects of cholinesterase inhibitors in Parkinson’s disease with dementia

Several evidences suggest that cholinergic deficits may significantly contribute to dementia in Parkinson's disease (PDD) and acetylcholinesterase inhibitors (ChEIs) have been reported to improve cognitive symptoms in PDD, without worsening parkinsonism. Nineteen PDD patients underwent brain perfusion SPECT with (99m)Tc-ethyl cysteinate dimer after 6 months ChEIs treatment in order to evaluate the functional correlates of clinical improvement. A clear-cut cognitive improvement was reported in PDD patients with a significant improvement of ADAS-cog total score as well as of subscores exploring executive functions (p<0.01). MMSE total score did not significantly change after ChEIs but the subscore of attention significantly improved after therapy (p<0.01). No difference in motor performance as evaluated by UPDRS was reported. SPM analysis showed a significant increase of perfusion (p < 0.0001) in bilateral cingulate, and frontal regions after ChEIs. Our data confirm the efficacy of ChEIs in the treatment of dementia associated with PD mainly on attention and executive functions, and the functional findings indicate that this cognitive improvement could be associated with a sort of pharmacological frontal "re-afferentation".

What Constitutes Clinical Evidence for Neuroprotection in Alzheimer Disease

The progression of Alzheimer disease (AD) corresponds to a prolonged course of neuronal loss in the cerebral cortex. Strategies aimed at reducing the rates of neuronal loss are therefore particularly important. The clinical measures to evaluate the disease-modifying effect of an intervention are readily confounded by any symptomatic benefit of the intervention. Thus, when testing putative neuroprotective agents that are known to have symptomatic effects, it can be difficult to separate the 2 effects. The hypothesis that cholinesterase inhibitors (ChEIs) only treat symptoms caused by cholinergic imbalances in AD is overly simplistic. Evidence has now accumulated that ChEIs have a neuroprotective, disease-modifying property. In this paper, to answer the question of what constitutes clinical evidence for neuroprotection in AD, we have reviewed clinical studies with specific designs, including "delaying end point," "withdrawal," and "randomized start" designs. We have also reviewed data on surrogate biomarkers of disease progression that may indicate a disease-modifying action. In addition, we have reviewed evidence indicating that ChEIs may protect cells in the brain of patients with AD. Among the clinical data suggesting a possible neuroprotective effect of ChEIs, the most rigorous published evidence comes from magnetic resonance imaging (MRI) hippocampal volumetric studies with donepezil.

Self-referential tags in the discourse of people with Alzheimer's disease

In a study of the discourse of 100 people with Alzheimer's disease treated for 12 months with donepezil, we observed that, as a group, they used a form of tag, described here as a self-referential tag (SRT), 14 times more frequently than did caregivers. Patients use SRTs to check propositions dependent on episodic memory as in I haven't seen the doctor recently, have I? and to monitor information flow as in I told you that already, didn't I? Based on criteria developed for distinguishing checking from monitoring tags, we document the type and frequency of patients' SRT use in the ACADIE corpus and analyze these in relation to standard measures of cognitive function (Mini Mental State Exam and Alzheimer's Disease Assessment Scale-cognitive sub-scale) at baseline and 12 months. Patients using monitoring SRTs (N=31), with or without checking SRTs, show significantly better cognitive test scores at 12 months, than are seen in patients who never use tags (N=29), or who only use checking tags (N=40). SRT use may be an independent measure of potential treatment responsiveness.

Cholinergically Mediated Augmentation of Cerebral Perfusion in Alzheimer's Disease and Related Cognitive Disorders: The Cholinergic-Vascular Hypothesis

The treatment of Alzheimer's disease (AD) with cholinesterase inhibitors (ChEIs) is based on the cholinergic hypothesis. This hypothesis fails to account for the global nature of the clinical effects of ChEIs, for the replication of these effects in other dementias, and for the strong and unpredictable intraindividual variation in response to treatment. These findings may be better explained by the premise that ChEIs primarily act by augmenting cerebral perfusion: the cholinergic-vascular hypothesis. This article will review the evidence from preclinical and clinical investigations on the vascular role of the cholinergic neural system. The clinical relevance of this hypothesis is discussed with respect to its interactions with the vascular and amyloid hypotheses of AD. Implications for treatment are indicated. Finally, we propose that the role of the cholinergic system in neurovascular regulation and functional hyperemia elucidates how the cholinergic deficit in AD contributes to the clinical and pathological features of this disease.

SPECT Follow-Up Study of Cerebral Blood Flow Changes During Donepezil Therapy in Patients with Alzheimer's Disease

BACKGROUND AND PURPOSE

Treatment with acetylcholinesterase inhibitors (AchEIs) is beneficial for patients with Alzheimer's disease (AD). But the clinical response varies. Functional neuroimaging techniques might allow objective evaluation of the topographic correlates of the effect of therapy on brain functioning. We attempted to evaluate the possible correlation between regional cerebral blood flow (rCBF) differences in patients with AD and response to donepezil hydrochloride (Donepezil) therapy.

METHODS

The subjects of this study were 51 consecutive patients with AD receiving Donepezil who underwent SPECT at baseline and 10-14 months later. We divided the patients into stabilized (n = 19) and nonstabilized (n = 32) subgroups based on changes in the Mini Mental State Examination (MMSE) score. Analysis of single-photon emission computed tomography (SPECT) data was done using 3-dimensional stereotactic surface projections (3D-SSP) and the stereotactic extraction estimation (SEE) method. We compared differences in rCBF between the two subgroups at baseline and follow-up, and between the baseline and follow-up in each subgroup.

RESULTS

Significant correlation was recognized between the mean Z score changes of the left frontal lobe, left limbic lobe, and MMSE change. There were no significant baseline differences in rCBF in any region of the brain between the two subgroups. At the study endpoint, the nonstabilized subgroup showed lower rCBF in the lateral and medial frontal lobes, limbic lobe, lower lateral temporal lobe, and cingulate gyrus compared to the stabilized subgroup. Both patient groups showed a significant post-treatment increase over baseline values in the frontal lobe, and the stabilized group had more extensive and intense increases in the lateral and medial frontal lobes and orbital surface.

CONCLUSIONS

Our study suggests that the diversity of clinical responses to Donepezil therapy in patients with AD is associated with rCBF changes, mainly in the frontal lobe. SPECT may be a promising tool to assess the impact of AchEI therapy on the brain function of patients with AD.

Genotype (cystatin C) and EEG phenotype in Alzheimer disease and mild cognitive impairment: A multicentric study

Previous findings demonstrated that haplotype B of CST3, the gene coding for cystatin C, is a recessive risk factor for late-onset Alzheimer's disease (AD; Finckh, U., von der Kammer, H., Velden, J., Michel, T., Andresen, B., Deng, A., Zhang, J., Muller-Thomsen, T., Zuchowski, K., Menzer, G., Mann, U., Papassotiropoulos, A., Heun, R., Zurdel, J., Holst, F., Benussi, L., Stoppe, G., Reiss, J., Miserez, A.R., Staehelin, H.B., Rebeck, G.W., Hyman, B.T., Binetti, G., Hock, C., Growdon, J.H., Nitsch, R.M., 2000. Genetic association of the cystatin C gene with late-onset Alzheimer disease. Arch. Neurol. 57, 1579-1583). In the present multicentric electroencephalographic (EEG) study, we analyzed the effects of CST3 haplotypes on resting cortical rhythmicity in subjects with AD and mild cognitive impairment (MCI) with the hypothesis that sources of resting EEG rhythms are more impaired in carriers of the CST3 B haplotype than non-carriers. We enrolled a population of 84 MCI subjects (42% with the B haplotype) and 65 AD patients (40% with the B haplotype). Resting eyes-closed EEG data were recorded in all subjects. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Results showed that the amplitude of alpha 1 (parietal, occipital, temporal areas) and alpha 2 (occipital area) was statistically lower in CST3 B carriers than non-carriers (P < 0.01). Whereas there was a trend towards statistical significance that amplitude of occipital delta sources was stronger in CST3 B carriers than in non-carriers. This was true for both MCI and AD subjects. The present findings represent the first demonstration of relationships between the AD genetic risk factor CST3 B and global neurophysiological phenotype (i.e., cortical delta and alpha rhythmicity) in MCI and AD subjects, prompting future genotype-EEG phenotype studies for the early prediction of AD conversion in individual MCI subjects.

Donepezil for dementia due to Alzheimer's disease

BACKGROUND

Alzheimer's disease is the most common cause of dementia in older people. One of the aims of therapy is to inhibit the breakdown of a chemical neurotransmitter, acetylcholine, by blocking the relevant enzyme. This can be done by a group of chemicals known as cholinesterase inhibitors.

OBJECTIVES

The objective of this review is to assess whether donepezil improves the well-being of patients with dementia due to Alzheimer's disease.

SEARCH STRATEGY

The Cochrane Dementia and Cognitive Improvement Group's Specialized Register was searched using the terms 'donepezil', 'E2020' and 'Aricept' on 12 June 2005. This Register contains up-to-date records of all major health care databases and many ongoing trial databases. Members of the Donepezil Study Group and Eisai Inc were contacted.

SELECTION CRITERIA

All unconfounded, double-blind, randomized controlled trials in which treatment with donepezil was compared with placebo for patients with mild, moderate or severe dementia due to Alzheimer's disease.

DATA COLLECTION AND ANALYSIS

Data were extracted by one reviewer (JSB), pooled where appropriate and possible, and the pooled treatment effects, or the risks and benefits of treatment estimated.

MAIN RESULTS

23 trials are included, involving 5272 participants. Most trials were of 6 months or less duration in selected patients. Available outcome data cover domains including cognitive function, activities of daily living, behaviour , global clinical state and health care resource costs. For cognition there is a statistically significant improvement for both 5 and 10 mg/day of donepezil at 24 weeks compared with placebo on the ADAS-Cog scale (-2.01 points MD, 95%CI -2.69 to -1.34, p<0.00001); -2.80 points, MD 95% CI -3.74 to -2.10, p<0.00001) and for 10 mg/day donepezil compared with placebo at 52 weeks (1.84 MMSE points, 95% CI, 0.53 to 3.15, p=0.006). The results show some improvement in global clinical state (assessed by a clinician) in people treated with 5 and 10 mg/day of donepezil compared with placebo at 24 weeks for the number of patients showing improvement or no change (OR 2.18, 95% CI 1.53 to 3.11, p=<0.0001, OR 2.38, 95% CI 1.78 to 3.19, p<0.00001). Benefits of treatment were also seen on measures of activities of daily living and behaviour, but not on the quality of life score . There were significantly more withdrawals before the end of treatment from the 10 mg/day (but not the 5 mg/day) donepezil group compared with placebo which may have resulted in some overestimation of beneficial changes at 10 mg/day. Benefits on the 10 mg/day dose were marginally larger than on the 5 mg/day dose. Two studies presented results for health resource use, and the associated costs. There were no significant differences between treatment and placebo for any item, the cost of any item, and for the total costs, and total costs including the informal carer costs. A variety of adverse effects were recorded, with more incidents of nausea, vomiting, diarrhoea, muscle cramps, dizziness, fatigue and anorexia (significant risk associated with treatment) in the 10 mg/day group compared with placebo but very few patients left a trial as a direct result of the intervention.

AUTHORS' CONCLUSIONS

People with mild, moderate or severe dementia due to Alzheimer's disease treated for periods of 12, 24 or 52 weeks with donepezil experienced benefits in cognitive function, activities of daily living and behaviour. Study clinicians rated global clinical state more positively in treated patients, and measured less decline in measures of global disease severity. There is some evidence that use of donepezil is neither more nor less expensive compared with placebo when assessing total health care resource costs. Benefits on the 10 mg/day dose were marginally larger than on the 5 mg/day dose. Taking into consideration the better tolerability of the 5 mg/day donepezil compared with the 10 mg/day dose, together with the lower cost, the lower dose may be the better option. The debate on whether donepezil is effective continues despite the evidence of efficacy from the clinical studies because the treatment effects are small and are not always apparent in practice .

Sources of cortical rhythms change as a function of cognitive impairment in pathological aging: a multicenter study

OBJECTIVE

The present study tested the hypothesis that cortical electroencephalographic (EEG) rhythms. change across normal elderly (Nold), mild cognitive impairment (MCI), and Alzheimer's disease (AD) subjects as a function of the global cognitive level.

METHODS

Resting eyes-closed EEG data were recorded in 155 MCI, 193 mild AD, and 126 age-matched Nold subjects. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). EEG cortical sources were estimated by LORETA.

RESULTS

Occipital delta and alpha 1 sources in parietal, occipital, temporal, and 'limbic' areas had an intermediate magnitude in MCI subjects compared to mild AD and Nold subjects. These five EEG sources presented both linear and nonlinear (linear, exponential, logarithmic, and power) correlations with the global cognitive level (as revealed by mini mental state examination score) across all subjects.

CONCLUSIONS

Cortical EEG rhythms change in pathological aging as a function of the global cognitive level.

SIGNIFICANCE

The present functional data on large populations support the 'transitional hypothesis' of a shadow zone across normality, pre-clinical stage of dementia (MCI), and AD.

Fronto-parietal coupling of brain rhythms in mild cognitive impairment: a multicentric EEG study

Electroencephalographic (EEG) data were recorded in 69 normal elderly (Nold), 88 mild cognitive impairment (MCI), and 109 mild Alzheimer's disease (AD) subjects at rest condition, to test whether the fronto-parietal coupling of EEG rhythms is in line with the hypothesis that MCI can be considered as a pre-clinical stage of the disease at group level. Functional coupling was estimated by synchronization likelihood of Laplacian-transformed EEG data at electrode pairs, which accounts for linear and non-linear components of that coupling. Cortical rhythms of interest were delta (2-4Hz), theta (4-8Hz), alpha 1 (8-10.5Hz), alpha 2 (10.5-13Hz), beta 1 (13-20Hz), beta 2 (20-30Hz), and gamma (30-40Hz). Compared to the Nold subjects, the AD patients presented a marked reduction of the synchronization likelihood (delta to gamma) at both fronto-parietal and inter-hemispherical (delta to beta 2) electrodes. As a main result, alpha 1 synchronization likelihood progressively decreased across Nold, MCI, and mild AD subjects at midline (Fz-Pz) and right (F4-P4) fronto-parietal electrodes. The same was true for the delta synchronization likelihood at right fronto-parietal electrodes (F4-P4). For these EEG bands, the synchronization likelihood correlated with global cognitive status as measured by the Mini Mental State Evaluation. The present results suggest that at group level, fronto-parietal coupling of the delta and alpha rhythms progressively becomes abnormal though MCI and mild AD. Future longitudinal research should evaluate whether the present EEG approach is able to predict the cognitive decline in individual MCI subjects.

Effect of oral administration of zanapezil (TAK-147) for 21 days on acetylcholine and monoamines levels in the ventral hippocampus of freely moving rats

Zanapezil (TAK-147 (3-[1benzylpiperdin-4-yl]-1-(2,3,4,5-tetrahydro-1 H-1-benzazepin-8-yl) propan-1-one fumarate)) is a selective acetylcholine (ACh) esterase inhibitor under investigation as a drug for Alzheimer's disease (AD) treatment. In this study, the effects of TAK-147 at 2 mg kg(-1) p.o. for 21 days, compared to donepezil (E2020), on the levels of ACh, catecolamines and indoleamines were investigated in the ventral hippocampus (VH) of freely moving rats by microdialysis-high-performance liquid chromatography. The results revealed that the VH contains 92.05+/-21.97 fmol 20 microl(-1) ACh and the following monoamines levels (pg 30 microl(-1)), norepinephrine (NE) 1.92+/-0.39, epinephrine (Epi) 1.91+/-0.183, 3-methoxy-4-hydroxyphenylglycol (MHPG) 11.53+/-3.22, normetanephrine 3.26+/-0.61, dopamine (DA) 0.77+/-0.23, 3,4-dihydroxyphenylacetic acid (DOPAC) 3.37+/-1.01, homovanillic acid (4-hydroxy-3-methoxyphenylacetic acid; HVA) 4.04+/-0.93, 3-methoxytyramine 0.64+/-0.13, serotonin (5-HT) 0.73+/-0.16 and 5-hydroxyindoleacetic acid (5-HIAA) 313.15+/-18.42. On the 21st day and prior to the last dose, TAK-147 increased ACh, Epi, DA and 5-HT, whereas E2020 increased MHPG, Epi and DA. Following the last dose, TAK-147 increased NE, whereas E2020 increased NE, ACh and 5-HT in addition to their effects prior to the last dose. TAK-147 decreased HVA : DA ratio, but only marginally decreased DOPAC : DA and 5-HIAA : 5-HT ratios. On the other hand, E2020 decreased ratios of HVA : DA, DOPAC : DA (prior to the last dose), and 5-HIAA : 5-HT (90-180 min after the last dose). Both drugs decreased MHPG : NE only at 180 min after the last dose. The results also showed that TAK-147 increased Epi : NE ratio prior to and for 120 min following the last dose, whereas E2020 increased the ratio only before the last dose. The present results show that TAK-147 at a subthreshold dose could differentially increase ACh and 5-HT, compared to MHPG increased by E2020. The last dose of each drug could extend their effects to other monoamines. The increase of the monoamines levels, in addition to that on the ACh, and decrease of their oxidation could be of value in the treatment of the AD, other dementic diseases and the cohort neurological disorders depending on the type of the monoamine underlying the disorder.

Longitudinal PET evaluation of cerebral glucose metabolism in rivastigmine treated patients with mild Alzheimer’s disease

In this study 11 patients with mild Alzheimer's disease (AD) were treated with the cholinesterase inhibitor rivastigmine (mean dose 8.6 +/- 1.3'mg) for 12 months and underwent positron emission tomography (PET) studies of cerebral glucose metabolism (CMRglc) and neuropsychological testing at baseline and after 12 months. An untreated group of 10 AD patients served as control group. While the untreated AD patients showed a significant decline of CMRglc in the temporo-parietal and frontal cortical regions after 12 months follow-up the rivastigmine-treated patients showed no decline in CMRglc in corresponding cortical brain regions. Furthermore, a significant dose-related increase in CMRglc was recorded in the right frontal association region after 12 months rivastigmine treatment. A positive correlation was observed between changes in CMRglc and several cognitive tests in patients receiving higher doses (10.5-12'mg) of rivastigmine. These results suggest a stabilization effect of rivastigmine on CMRglc in mild AD patients receiving long-term rivastigmine treatment.

The cholinesterase inhibitor, phenserine, improves Morris water maze performance of scopolamine-treated rats

Male Fischer-344 rats (n = 38) at 5 months old were tested in a Morris water maze to determine if treatment with the cholinesterase inhibitor, phenserine (PHEN), would overcome a learning impairment induced by scopolamine (SCOP), a muscarinic cholinergic receptor antagonist. Each rat was randomly assigned to one of five groups to receive two intraperitoneal injections 60 and 30 min, prior to testing, respectively, as follows: (1) saline-saline (SAL); (2) saline-1.0 mg/kg (SCOP); (3) 2 mg/kg PHEN- SCOP (PHEN2); (4) 4 mg/kg PHEN-SCOP (PHEN4); and (5) 1 mg/kg PHEN-SAL (PHEN1). Maze testing occurred across 5 days with 4 days of acquisition trials (4 trials per day) and a fifth day consisting of a single 120 sec probe trial. PHEN1 and SAL were combined into one control (CON) group for purposes of statistical analysis for both acquisition and probe trials as comparison of the two groups revealed that they did not significantly differ on any measure. SCOP-treated rats were significantly impaired compared to CON in learning the location of the submerged platform as measured by latency to locate the platform and the distance traversed to find the platform across days of testing. The PHEN4 group had significantly lower latencies and traveled a shorter distance to reach the submerged platform when compared to SCOP on the fourth day of trials while the PHEN2 group traveled more directly to the submerged platform but did not have shorter latencies than the SCOP group. For probe trials, CON rats swam closer to the target area (a measure of proximity to the removed platform) than did all other groups, and the PHEN4 group swam in an area more proximate to the target area than did the SCOP-treated group. These findings demonstrate the ability of this drug to improve learning when cholinergic function has been impaired in a spatial memory task.

Effects of cholinergic drugs and cognitive training on dementia

A study was performed on patients with Alzheimer's disease (AD) in order to evaluate the efficacy of a combined treatment (donepezil plus cognitive training) in both cognitive processes and affective states. Eighty-six subjects, 25 men and 61 women, with an average age of 75.58 years, were studied. Almost all the subjects had a basic educational level. Donezepil was administered at a dose of 10 mg daily along with cognitive treatment involving images of everyday life and reminiscent music; the sessions took place on Monday to Friday and lasted three quarters of an hour. The study lasted 12 months. Subjects underwent test-retest with the following tests: Mini-Mental State Examination (MMSE), the cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog); the Geriatric Depression Scale (GDS) and the overall deterioration scale (FAST). The results showed that subjects receiving the combined treatment had a better response than those who did not receive any cognitive training. These subjects' MMSE score decreased by 3.24 on average. The affective symptomatology of those receiving only drug treatment improved whereas the cognitive processes did not.

Cerebral Perfusional Effects of Cholinesterase Inhibitors in Alzheimer Disease

Cholinesterase (ChE) inhibitors improve or stabilize cognitive impairment in patients with Alzheimer disease (AD). However, the regional metabolic and perfusion correlates of treatment with ChE inhibitors are not fully known. Twenty-four patients with mild to moderate AD were evaluated with Tc-ethyl cysteinate dimer (ECD) single-photon-emission CT scanning (SPECT), before and after 4.3 +/- 1.1 months of treatment with ChE inhibitors (donepezil, rivastigmine). Clinical evaluations included the Mini-Mental State Examination (MMSE) as well as the Neuropsychiatric Inventory (NPI). Inclusion criterion was a clear favorable response to therapy with ChE inhibitors (MMSE improvement of at least 2 points; total NPI improvement of at least 4 points). SPECT data were analyzed by Statistical Parametric Mapping (SPM 99, Wellcome, Department of Cognitive Neurology, London, UK). SPM analysis showed a significant increase (P < 0.01) of regional cerebral perfusion (rCBF) after short-term ChE inhibitor therapy with respect to baseline in the right anterior cingulate, the dorsolateral prefrontal, and the temporoparietal areas bilaterally. These data suggest that cognitive or behavioral benefits after ChE inhibitor therapy are related to a clear increase of rCBF in crucial areas specifically involved in the attentional and limbic networks.

Cholinergic enhancement of frontal lobe activity in mild cognitive impairment

Cholinesterase inhibitors positively affect cognition in Alzheimer's disease (AD) and other conditions, but no controlled functional MRI studies have examined where their effects occur in the brain. We examined the effects of donepezil hydrochloride (Aricept) on cognition and brain activity in patients with amnestic mild cognitive impairment (MCI), a diagnosis associated with a high risk of developing AD. Nine older adults with MCI were compared with nine healthy, demographically matched controls. At baseline, patients showed reduced activation of frontoparietal regions relative to controls during a working memory task. After stabilization on donepezil (5.7 +/- 1.7 weeks at 10 mg) patients showed increased frontal activity relative to unmedicated controls, which was positively correlated with improvement in task performance (r = 0.49, P = 0.05) as well as baseline hippocampal volume (r = 0.62, P < 0.05). The patients' overall cognitive function was stable or improved throughout the study. Short-term treatment with a cholinesterase inhibitor appears to enhance the activity of frontal circuitry in patients with MCI, and this increase appears to be related to improved cognition and to baseline integrity of the hippocampus. These relationships have implications for understanding the mechanisms by which cognition-enhancing medications exert their effects on brain function and for the use of functional MRI in early detection and treatment monitoring of AD and MCI.

Comparison of the effect of TAK-147 (zanapezil) and E-2020 (donepezil) on extracellular acetylcholine level and blood flow in the ventral hippocampus of freely moving rats

The effects of zanapezil (TAK-147) and donepezil (E2020) on extracellular acetylcholine (ACh) levels were investigated by HPLC-microdialysis of ventral hippocampus (VH) in freely moving intact rats. The results showed that the basal ACh release rate in the VH is 116.7 +/- 12.4 to 158.4 +/- 22.86 fmol/20 microl. At 2, 5 and 10 mg/kg, single p.o., each drug increased ACh level by 9.4%, 106.5%, 50.8% (TAK-147) and 14.8%, 76.1%, 120.94% (E2020), respectively. The ED50 values were 4.52 mg/kg (1.43 - 14.29; R=0.52) and 4.07 mg/kg (1.77 - 9.37; R=0.985) for TAK-147 and E2020, respectively. Analysis of data revealed that the relative TAK-147/E2020 potency ratio is 0.773, but the effect of E2020 was accompanied by more prominent skeletal muscle fasciculation, gnawing, increased defecation and to lesser extent salivation. Moreover, the significant effect of TAK-147 was observed earlier (20 min) than E2020 (60 min). In this study, we also investigated the effect of both drugs at dose of 5 mg/kg p.o. on blood flow in the VH using Laser Doppler Flowmetry. The results showed that the average blood flow rate in the VH is 6.5 +/- 0.9 ml/min/100 g. TAK-147 did not change blood flow, but E2020 increased blood flow in a biphasic manner. The first increment was obtained between 5 and 40 min (11.5 +/- 2.2 to 12.7 +/- 2.2 ml/min/100 g), and the second one 80-105 min (10.7 +/- 1.6 to 13.4 +/- 3.6 ml/min/100 g). In conclusion, the present results indicate that both TAK-147 and E2020 increase ACh level in the VH. E2020 showed greater potency than TAK-147, but it induced more fasciculation and other side effects than TAK-147. Moreover, the blood flow increasing properties of E2020 could be beneficial in some patients with Alzheimer' disease especially those with chronic vascular dementia, but at the same time, it could also indicate less specific ACh increasing activity than TAK-147 and higher risk of cerebral hemorrhage. On the other hand, the fast and specific effect of TAK-147 may be useful for cure of early stages of Alzheimer's disease (AD).

Quantitative EEG and perfusional single photon emission computed tomography correlation during long-term donepezil therapy in Alzheimer's disease

OBJECTIVE

There is an increasing interest in the effects of the acetylcholinesterase inhibitors (AChEIs) in Alzheimer's disease (AD), as investigated by means of objective, neurophysiological tools. In an open-label study, we evaluated the neurophysiological effects of chronic administration of donepezil to AD patients, by means of a correlative approach between quantitative EEG (qEEG) and perfusional brain single photon emission computed tomography (SPECT).

METHODS

Sixteen patients (mean age: 74.8+/-7.9 years) with mild to moderate AD (MMSE score >13, mean: 20.7+/-4.6) underwent qEEG and SPECT examinations at the time of diagnosis (t0) and after approximately 1 year of donepezil therapy (t1). The brain SPECT (99mTc-hexamethylpropyleneamine oxime) was performed by means of a high-resolution SPECT camera; the qEEG was recorded from 19 scalp electrodes by average reference and digitized at 512 Hz. The mean frequency (MF) value of the mean power spectrum (fast Fourier transform) from 4 brain regions (one frontal and one temporal-parietal in each hemisphere) was chosen for statistical analysis. Changes in MMSE score and qEEG-MF values between t0 and t1 were assessed by analysis of variance. SPECT differences between t0 and t1, as well as the relationships between SPECT and qEEG changes, were assessed by statistical parametric mapping (SPM 99; height threshold: P=0.001 at cluster level).

RESULTS

Between t0 and t1, the MMSE score significantly (P<0.05) decreased (from 20.7+/-4.64 to 19.1+/-5.09; 95% confidence interval: 1.14) and qEEG was unchanged. There was no regional perfusion decrease; a small area of relative perfusion increase was observed, including the right occipital cuneus and the left lingual gyrus. A positive correlation was found between the right frontal MF and brain perfusion in the left superior parietal lobule. A post hoc SPM analysis (height threshold: P=0.01) showed a positive correlation between brain perfusion and each of the 4 qEEG MF values in the left parietal lobe, including the precuneus, the superior parietal lobule, and the post-central gyrus.

CONCLUSIONS

The posterior parietal region, which is involved in memory and attention, is often affected by hypoperfusion in AD, as a likely consequence of disconnection from the atrophic mesial temporal cortex. Metabolic activation induced by AChEIs may especially influence this disconnected but still not grossly impaired area, which could be one of the pathophysiological substrates of the cognitive effects of AChEIs. The modest topographical sensitivity of qEEG, reflecting the rather diffuse changes in AD, is further confirmed.

The effect of cholinesterase inhibitors on the regional blood flow in patients with Alzheimer's disease and vascular dementia

The effects of therapy with cholinesterase inhibitors (ChE-I) on regional cerebral blood flow (rCBF) disturbances were investigated by means of single photon emission computed tomography (SPECT). The changes in rCBF were compared with the results of the medical examination and neuropsychological tests. The sample consisted of 41 patients with the Alzheimer's dementia (AD) and vascular dementia (VaD). The effect of ChE-I (rivastigmine) treatment was studied on 33 patients, while the nontreated control group consisted of 8 patients. In the treated patients, an increase in the rCBF was observed, while the scores of the neuropsychological tests decreased slightly. In the VaD group, the increase in rCBF was more significant in the frontal regions, whereas in the group with AD in the temporal regions, respectively. In the nontreated patients, a decrease of both rCBF and scores of neuropsychological tests were observed. The scores of the neuropsychological tests correlated with the results of rCBF. Increased levels of acetylcholine in the brain after ChE-I treatment may support the cholinergic regulation of rCBF, and in result increase it. Such effects seem to be more pronounced in the more affected brain regions.

Effect of N-(4-Acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate (FK960), an antidementia drug with a novel mechanism of action, on regional cerebral blood flow and glucose metabolism in aged rhesus macaques studied with positron emission tomography

Effect of N-(4-acetyl-1-piperazinyl)-p-fluorobenzamide monohydrate (FK960), a putative antidementia drug with a novel mechanism of action, on regional cerebral blood flow (rCBF) and regional cerebral metabolic rate of glucose (rCMRglc) was examined in conscious aged rhesus macaques using positron emission tomography. Seven aged (21.6 +/- 2.7 years) male rhesus macaques were subjected. FK960 was intramuscularly administered at doses of 0, 0.01, 0.1, or 1 mg/kg for seven consecutive days, in randomized order and in a blinded manner. Each subject was scanned four times in all, with at least 3-week intervals, after treatment with saline or three doses of FK960. Significant increases in rCBF in the left temporal and left frontal cortex, and in rCMRglc in the right hippocampus with adjacent cortex, were observed in the treatment group with 1 mg/kg FK960, without affecting any other cardiovascular and respiratory variables. No statistically significant change in any region was observed at doses of 0.01 or 0.1 mg/kg. These results suggested that FK960 restored the rCBF and rCMRglc deficits in brain areas responsible for cognitive functioning in aged rhesus macaques.