Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.1.8 (cholinesterase)
12,691 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

As the population ages and Alzheimer's disease (AD) becomes more prevalent, nursing facilities will be faced with managing more AD patients than in previous decades. Managing this population will pose a significant challenge for the resources of long-term care facilities. In short- and long-term studies, cholinesterase (ChE) inhibitor treatment has been shown to benefit the symptoms of mild to moderate AD. Donepezil trials have extended this finding to patients with moderate to severe AD as well as the more severe symptoms of AD patients residing in nursing home settings. Results from long-term ChE inhibitor trials and the benefits that may be gained by treating AD patients residing in nursing facilities are presented.
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PMID:Long-term cholinesterase inhibitor therapy for Alzheimer's disease: implications for long-term care. 1270 22

Visual hallucinations (VHs) are common psychiatric symptoms in patients with long-standing Parkinson's disease (PD). Treatment with neuroleptics or withdrawal of anti-PD drugs may improve VHs but will worsen motor dysfunctions. The authors report on 3 patients with long-standing PD who were treated with the cholinesterase inhibitor donepezil for the treatment of VHs. Each received a daily dose of 5 mg of donepezil, after reducing or discontinuing anti-PD medications had failed to relieve the VHs. In 2 patients (patient 1, 2), donepezil decreased VHs without worsening motor dysfunctions. In addition, the cognitive status of patient 2 improved. In patient 3, donepezil also resolved VHs, but delusions developed during treatment. After discontinuing donepezil, delusions disappeared and VHs reappeared. Donepezil may ameliorate visual hallucinations in PD patients, but controlled, double-blind trials are necessary to further clarify the effect of this drug on VHs in PD.
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PMID:The beneficial effect of donepezil on visual hallucinations in three patients with Parkinson's disease. 1296 63

The cholinergic hypothesis suggests that Alzheimer's disease (AD) results from a selective loss in cholinergic neurons with decreased acetylcholine levels. Treatments that increase the level of acetylcholine would be expected to provide clinical benefit. Clinical trials of dietary precursors of acetylcholine and muscarinic receptor agonists have been unsuccessful. Further research is needed to confirm whether nicotine or nicotinic agonists are of value. The most successful approach has been to increase acetylcholine levels by inhibiting cholinesterase function. A number of cholinesterase inhibitors (ChEI) show clinical efficacy including phyostigmine but it is poorly tolerated. Tacrine, the first ChEI to be licensed for AD, needs frequent administration and causes a specific reversible hepatotoxicity. Three ChEI, donepezil, rivastigmine and galantamine are widely available. They are effective in mild to moderate (and possibly severe) AD. Tolerability is improved by slow dose titration and there are a significant number of non-responders. Donepezil appears to be effective, the simplest to use and the best tolerated. Rivastigmine is effective but less well tolerated: galantamine is also very effective with intermediate tolerability. Although there are pharmacological differences between the three compounds, it remains uncertain whether these are clinically relevant. There are still unanswered questions. It is difficult to predict who will respond to the drugs and it is unclear how long treatment benefits last. At present there are little data to support the suggestion of activity beyond symptomatic benefit. Trials are also being conducted in Mild Cognitive Impairment, other dementias and other conditions where cognitive impairment is a problem.
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PMID:Have cholinergic therapies reached their clinical boundary in Alzheimer's disease? 1297 45

1. The effects of donepezil, one of the most common cholinesterase inhibitors used for treatment of Alzheimer's disease, were studied on nicotinic receptors (nAChRs)-mediated postsynaptic currents, in dopaminergic neurons of the substantia nigra pars compacta, using the patch-clamp recording technique in slice preparations. 2. Donepezil (10-100 microM) selectively and reversibly depressed nicotine currents, induced by brief puffer pulses, through a glass micropipette positioned above the slice. 3. The peak amplitude fading of the responses generated by repeated test applications of low doses of nicotine was accelerated by donepezil, while it slowed the recovery of nicotine currents after a large, desensitising, dose of the same agonist. 4. Donepezil depressed even maximal responses to nicotine, revealing a noncompetitive mechanism of action; moreover, the inhibition of nAChRs was voltage and time independent. 5. Pretreatment with vesamicol or methamidophos did not prevent the reduction of nicotine-induced currents. The data indicated direct effect on nAChR, independent from the activity of donepezil as cholinesterase inhibitor.
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PMID:Donepezil modulates nicotinic receptors of substantia nigra dopaminergic neurones. 1474 6

Cholinesterase inhibitors vary in their selectivity for acetylcholinesterase versus butyrylcholinesterase. We examined several cholinesterase inhibitors and assessed the relative role of acetylcholinesterase versus butyrylcholinesterase inhibition in central and peripheral responses to these medications. Donepezil and icopezil are highly selective for acetylcholinesterase, whereas tacrine and heptylphysostigmine demonstrated greater potency for butyrylcholinesterase over acetylcholinesterase. All four compounds increased acetylcholine levels in mouse brains. Dose-response curves for tremor (central effect) and salivation (peripheral effect) showed that donepezil and icopezil possess a more favourable therapeutic index than the nonselective inhibitors, tacrine and heptylphysostigmine. Co-administration of the selective butyrylcholinesterase inhibitor tetraisopropylpyrophosphoramide (iso-OMPA) potentiated peripheral, but not central, effects of the selective acetylcholinesterase inhibitor icopezil. The improved therapeutic index observed in mice with icopezil is due to a high degree of selectivity for acetylcholinesterase versus butyrylcholinesterase, suggesting that high selectivity for acetylcholinesterase may contribute to the clinically favourable tolerability profile of agents such as donepezil in Alzheimer's disease patients.
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PMID:Pharmacology of selective acetylcholinesterase inhibitors: implications for use in Alzheimer's disease. 1475 2

Studies in animals exploring the antagonism of the cholinesterase inhibitors soman and sarin have shown that pretreatment with low doses of the centrally acting cholinesterase inhibitor, physostigmine, alone or in conjunction with the centrally acting anticholinergic agent, scopolamine, is effective against their lethality and toxicity. The current study evaluated the effects of pretreatment with the oral anticholinesterase agent, donepezil (Aricept, 2.0 mg/kg), used to treat Alzheimer's disease, with and without scopolamine in decreasing the hypothermic, hypokinetic, and diarrhea-inducing effects of the irreversible long-acting cholinesterase inhibitor diisopropyl fluorophosphate (DFP, 1.0 mg/kg) in adult Flinders sensitive line (FSL) male rats. Donepezil alone and donepezil plus scopolamine (0.1 mg/kg) to a greater extent antagonized the decrease in temperature, hypoactivity, and induction of diarrhea due to DFP observed at 4 h after its administration. However, donepezil alone induced hypothermia at 1 and 2 h after treatment. Therefore, these preliminary findings are encouraging, but many additional studies are needed to establish the effectiveness of donepezil as a prophylactic agent against irreversible cholinesterase inhibition by DFP.
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PMID:Antagonism of anticholinesterase (DFP) toxicity by donepezil plus scopolamine: a preliminary study. 1475 62

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.
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PMID:Cholinergic enhancement of frontal lobe activity in mild cognitive impairment. 1514 Aug 13

Currently, cholinergic therapies for Alzheimer's disease (AD) have been developed and widely accepted based upon an observation that presynaptic cholinergic neurons in the basal nucleus of Meynert that widely project to the cerebral cortices are consistently damaged in AD brains. Since it is likely that the loss of central cholinergic activity may be associated with cognitive worsening in patients with AD, it is hypothesized that cholinergic augmentation could improve the cognitive ability of patients with AD. Cholinesterase inhibitors represent one way of implementing this strategy by inhibiting the breakdown of acetylcholine and increasing its availability in synapses. Indeed, several recent clinical trials of donepezil, galanthamine and rivastigmine have come to the conclusion that these cholinesterase inhibitors have overall beneficial effects in cognitive as well as global functions. American Academy of Neurology recommended a use of cholinesterase inhibitors as a first choice medicine in the treatment of AD. All 3 major studies of Donepezil from USA, Europe and Japan have reached the same conclusion favoring Donepezil in the treatment of mild to moderate AD. Donepezil can also be used as a safe and efficacious drug in the elderly aged 85 or older. Clinical trial of galantamine is in progress in Japan. Moreover, herbal medicines named kami-untan-to and hachimi-jiou-gan have been shown to be beneficial in some priority studies with a small sample size. It is critically needed to widen therapeutic windows in the treatment of AD.
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PMID:[Current therapies in dementia]. 1523 49

Cholinesterase inhibitors used to treat the symptoms of Alzheimer's disease (AD) inhibit both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), albeit to different degrees. Because central and peripheral neurons, including intrinsic cardiac neurons located on the surface of the mammalian heart, express both BuChE and AChE, we studied spontaneously active intrinsic cardiac neurons in the pig as a model to assess the effects of inhibition of AChE compared to BuChE. Neuroanatomical experiments showed that some porcine intrinsic cardiac neurons expressed AChE and/or BuChE. Enzyme kinetic experiments with cholinesterase inhibitors, namely, donepezil, galantamine, (+/-) huperzine A, metrifonate, rivastigmine, and tetrahydroaminoacridine, demonstrated that these compounds differentially inhibited porcine AChE and BuChE. Donepezil and (+/-) huperzine A were better reversible inhibitors of AChE, and galantamine equally inhibited both the enzymes. Tetrahydroaminoacridine was a better reversible inhibitor of BuChE. Rivastigmine caused more rapid inactivation of BuChE as compared to AChE. Neurophysiological studies showed that acetylcholine and butyrylcholine increase or decrease the spontaneous activity of the intrinsic cardiac neurons. Donepezil, galantamine, (+/-) huperzine A, and tetrahydroaminoacridine changed spontaneous neuronal activity by about 30-35 impulses per minute, while rivastigmine changed it by approximately 100 impulses per minute. It is concluded that (i) inhibition of AChE and BuChE directly affects the porcine intrinsic cardiac nervous system, (ii) the intrinsic cardiac nervous system represents a suitable model for examining the effects of cholinesterase inhibitors on mammalian neurons in vivo, and (iii) the activity of intrinsic cardiac neurons may be affected by pharmacological agents that inhibit cholinesterases.
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PMID:Cholinesterase inhibitors modify the activity of intrinsic cardiac neurons. 1524 45

Increasing evidence suggests that the cholinergic system is involved in the pathogenesis of schizophrenia. Donepezil, a central cholinesterase inhibitor, improves psychotic symptomatology in demented patients, however, evidence for its role in the management of active psychosis in schizophrenia remains limited. An 18-week double blind cross-over study was conducted in which eight patients were randomly assigned to either donepezil (5 mg/day for the first 4 weeks and 10 mg/day for the following 4 weeks) or placebo as augmentation treatment to clozapine. After this initial phase, there was a 2-week washout period of the study medication after which the same regimen was crossed over at the same dose and for the same period (8 weeks). No significant difference was noted in the total positive and negative symptom scale scores when donepezil was compared with placebo (16.7%+12.97% vs 3.20%+13.94% respectively, p = 0.18). However, three patients improved (>15%) in the total PANSS scores (37.03%, 16.6% and 25.33%) during the donepezil treatment phase, while only one patient improved (20.87%) during the placebo phase. No differences were noted in the Calgary depression scale (p = 0.305), Simpson Angus scale (p = 0.374), clinical global impression-improvement scale (p = 0.23) and clinical global impression-severity of illness scores (p = 0.116). Although this preliminary study failed to demonstrate a clear effect of donepezil augmentation in clozapine treated chronic schizophrenia patients, it seems that the subtle positive effect of donepezil observed in some of our patients should encourage further investigation in a larger sample of this patient subpopulation.
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PMID:Donepezil augmentation of clozapine monotherapy in schizophrenia patients: a double blind cross-over study. 1525 26


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