Clinical effects of choline in Alzheimer's disease

Brian Collier (1940-2024)

Dr. Brian Collier, the former Editor-in-Chief of the Journal of Neurochemistry from 1996 to 2006, passed away January 4th, 2024. Brian's illustrious career spanned the fields of neurochemistry and pharmacology. He published his findings on mechanisms of acetylcholine synthesis and storage in the Journal of Neurochemistry, and his contributions remain landmarks in neurochemical research.

Gut dysbiosis, defective autophagy and altered immune responses in neurodegenerative diseases: Tales of a vicious cycle

The human microbiota comprises trillions of symbiotic microorganisms and is involved in regulating gastrointestinal (GI), immune, nervous system and metabolic homeostasis. Recent observations suggest a bidirectional communication between the gut microbiota and the brain via immune, circulatory and neural pathways, termed the Gut-Brain Axis (GBA). Alterations in gut microbiota composition, such as seen with an increased number of pathobionts and a decreased number of symbionts, termed gut dysbiosis or microbial intestinal dysbiosis, plays a prominent role in the pathogenesis of central nervous system (CNS)-related disorders. Clinical reports confirm that GI symptoms often precede neurological symptoms several years before the development of neurodegenerative diseases (NDDs). Pathologically, gut dysbiosis disrupts the integrity of the intestinal barrier leading to ingress of pathobionts and toxic metabolites into the systemic circulation causing GBA dysregulation. Subsequently, chronic neuroinflammation via dysregulated immune activation triggers the accumulation of neurotoxic misfolded proteins in and around CNS cells resulting in neuronal death. Emerging evidence links gut dysbiosis to the aggravation and/or spread of proteinopathies from the peripheral nervous system to the CNS and defective autophagy-mediated proteinopathies. This review summarizes the current understanding of the role of gut microbiota in NDDs, and highlights a vicious cycle of gut dysbiosis, immune-mediated chronic neuroinflammation, impaired autophagy and proteinopathies, which contributes to the development of neurodegeneration in Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, amyotrophic lateral sclerosis and frontotemporal lobar degeneration. We also discuss novel therapeutic strategies targeting the modulation of gut dysbiosis through prebiotics, probiotics, synbiotics or dietary interventions, and faecal microbial transplantation (FMT) in the management of NDDs.

Detection of volatile malodorous compounds in breath: current analytical techniques and implications in human disease

For the last few decades intense scientific research has been placed on the relationship between trace substances found in exhaled breath such as volatile organic compounds (VOC) and a wide range of local or systemic diseases. Although currently there is no general consensus, results imply that VOC have a different profile depending on the organ or disease that generates them. The association between a specific pathology and exhaled breath odor is particularly evident in patients with medical conditions such as liver, renal or oral diseases. In other cases the unpleasant odors can be associated with the whole body and have a genetic underlying cause. The present review describes the current advances in identifying and quantifying VOC used as biomarkers for a number of systemic diseases. A special focus will be placed on volatiles that characterize unpleasant breath 'fingerprints' such as fetor hepaticus; uremic fetor; fetor ex ore or trimethylaminuria.

Oral choline supplementation for postoperative pain

BACKGROUND

Activation of nicotinic receptors with nicotine has been shown to reduce post-surgical pain in clinical and preclinical studies. Choline is a selective agonist at α7-type nicotinic receptors that does not have addictive or sympathetic activating properties. It is anti-nociceptive in animal studies. We conducted a double-blind randomized trial of oral choline supplementation with lecithin to aid in the treatment of pain after gynaecological surgery.

METHODS

Sixty women having open gynaecological surgery were randomly assigned to receive 20 g of lecithin before surgery or placebo. Plasma choline concentration and tumour necrosis factor (TNF) were measured. Pain report was the primary outcome measure.

RESULTS

We achieved a small but statistically significant increase in choline after surgery with oral supplementation. Plasma TNF was not decreased and pain report was not different between groups at rest or with movement. There were no adverse effects of treatment.

CONCLUSIONS

Oral supplementation with lecithin during the perioperative period resulted in very slow absorption and thus only a small increase in plasma choline was achieved. This concentration was inadequate to reduce TNF as has been shown in other studies. The absence of an anti-inflammatory effect was likely related to our failure to demonstrate efficacy in pain reduction.

Trimethylaminuria (fish-odour syndrome) and oral malodour

A small but important percentage of oral malodour cases have an extra-oral aetiology and certain of these fall into the category of 'blood-borne halitosis'. Odoriferous substances generated within the body and transported to the lungs via the circulatory system may, if sufficiently volatile, leave with the exhaled air and impart a foetid odour to the breath. The aliphatic tertiary amine, trimethylamine, is such a volatile compound that is generated to excess in patients with a metabolic disorder known as trimethylaminuria (fish-odour syndrome). This article highlights this condition and draws attention to its potential role in the causation of recalcitrant oral malodour.

The cholinesterase inhibitors

Dementia is a serious and growing problem that presents enormous burdens to patients, their families, and national healthcare systems throughout the world. In the United States, there are currently two classes of psychopharmacologic agents approved for the treatment of Alzheimer's disease: the cholinesterase inhibitors, which are approved for use in patients with mild to moderate disease, and memantine, an N-methyl-D-aspartate (NMDA) receptor antagonist, which is approved for treatment of moderate to severe illness. Three cholinesterase inhibitors are in general clinical use, each of which has a distinct pharmacokinetic, pharmacodynamic, and side-effect profile. In addition, there is growing research and clinical evidence of the effectiveness of the cholinesterase inhibitors in patients who are in the more advanced stages of Alzheimer's dementia as well as in patients with other forms of dementia.

Pharmacologic treatments of dementia

The management of dementia patients encompasses pharmacologic, behavioral, and psychosocial intervention strategies. Before pharmacologic intervention is instituted, it is important that sources of excess disability and comorbidity be eliminated or reduced. Identification of comorbid medical and psychiatric conditions, such as depression and delirium, should be identified and appropriately treated. Providing caregivers with education, support, and practical advice is a critical component of the management of the demented patient. The current standard of care for pharmacologic management of the cognitive and functional disabilities of AD consists of the combination of a cholinesterase inhibitor and high-dose vitamin E. This standard is based on the results of large-scale, double-blind, placebo-controlled trials. Cholinesterase inhibitors are the only FDA-approved pharmacologic treatments for AD. Cholinesterase inhibitors have been shown to be effective in the treatment of the cognitive, behavioral, and functional deficits of AD. Large-scale placebo-controlled trials of tacrine, donepezil, rivastigmine, and galantamine have demonstrated moderate benefits in patients with mild to moderate AD. Donepezil, rivastigmine, and galantamine are the first-line choices in the treatment of AD because of their lack of hepatotoxicity, ease of administration, few significant drug-drug interactions, and mild to moderate side effects. There are few contraindications to the use of cholinesterase inhibitors. Known hypersensitivity to a specific drug or its derivatives is the only true contraindication. Cautious administration of cholinesterase inhibitors is advised in patients who have a previous history of allergy or adverse reactions to prior cholinesterase inhibitors, severe liver disease, preexisting bradycardia, peptic ulcer disease, current alcoholism, asthma, or chronic obstructive pulmonary disease. Nausea, vomiting, diarrhea, and anorexia are the most common side effects of cholinesterase inhibitors. These gastrointestinal side effects can be minimized by gradual dose increases, administration with food, adequate hydration, and judicious use of an antiemetic. Vitamin E has been demonstrated to slow the progression of AD in several small and one large placebo-controlled trials. Because of its low cost and safety, it is recommended in addition to a cholinesterase inhibitor for the treatment of AD. There are no FDA-approved treatments for DLB and VaD. One small placebo-controlled trial demonstrated that rivastigmine may be effective in the treatment of DLB. More large-scale placebo-controlled trials are needed to confirm the results of this study. Treatment of VaD focuses on the control, identification, and management of cerebrovascular disease and vascular risk factors. Although there are no peer-reviewed reports on the efficacy of cholinesterase inhibitors for VaD or mixed AD/VaD, early reports suggest that these agents may also be effective for mixed AD/VaD. The indications for the use of cholinesterase inhibitor drugs are eventually likely to broaden to include DLB, mixed AD/VaD, and AD in its more advanced stages.

Treatment of Alzheimer's disease: rationale and strategies

This article reviews the rationale and provides a progress update regarding the major treatment strategies being developed for the prevention and treatment of Alzheimer's disease. Various therapeutic areas are discussed, including acetylcholinesterase inhibitors and other cholinergic agents, antioxidants, anti-inflammatory drugs, hormone replacement therapy, antiamyloid treatment, and neurotrophic agents.

Essential nature of choline with implications for total parenteral nutrition

Choline is known to be important in many metabolic pathways; at this time, however, it is not considered an essential nutrient for human beings. Current evidence strongly suggests that choline is "conditionally essential," particularly for patients receiving total parenteral nutrition (TPN). Studies in patients receiving long-term TPN have shown that low levels of plasma choline are common and can be associated with hepatic steatosis. Treatment of these patients with oral administration of choline improved plasma levels and decreased hepatic fat content; however, oral choline supplements are associated with poor compliance. More recently, investigators have evaluated intravenous administration of choline as a treatment for TPN-associated hepatic steatosis in patients with documented subnormal plasma free-choline levels. Initial results indicate that intravenous administration of choline may be an effective treatment for TPN-associated hepatic dysfunction.

Effects of a single intravenous dose of scopolamine on the quantitative EEG in Alzheimer's disease patients and age-matched controls

Quantitative EEG (qEEG) was evaluated in Alzheimer's disease (AD) patients and age-matched controls following the administration of a single acute intravenous dose of scopolamine. Eleven AD patients and 8 cognitively intact age-matched controls underwent qEEG in baseline conditions, following double-blind intravenous administration of 0.5 mg scopolamine or placebo. At baseline, AD patients had significantly decreased absolute and relative alpha and increased relative theta amplitudes. In both groups, scopolamine administration was followed by a decrease in absolute and relative alpha amplitude, and increase in the absolute and relative delta activity. The increase in the absolute and relative delta amplitude by scopolamine was significantly more prominent in the controls; the decrease of alpha activity, while larger in controls, was not statistically different from AD. We conclude that scopolamine affects the change in delta amplitude differently in AD patients and controls, probably reflecting the reduced cholinergic tone in AD.

Advances in the pharmacotherapy of Alzheimer's disease

The authors reviewed the literature on the agents proposed for the treatment of Alzheimer's disease (AD). Different classes of drugs have been tested for this indication including psychostimulants, anticoagulants, vasodilators, hyperbaric oxygen, hormones, nootropics, cholinomimetics, monoaminergics and neuropeptides without conclusive evidence of being beneficial for the treatment of this condition. Among the cholinomimetics recent research data seems to indicate that they might produce modest benefits in mild-to-moderate AD patients. Recently, other drugs have also been proposed including neurotrophic factors, phosphatidylserine, angiotension [corrected] converting enzyme (ACE) inhibitors, calcium channel blockers, acetyl-L-carnitine, xanthine derivatives, anti-inflammatory agents, aluminum chelate agents, and D-cycloserine. Of these new strategies few hold promise of more substantial benefits for AD, with the possibility of altering the course of the disease, but these drugs await confirmatory trials.

Spatial learning deficits in the aged rat: neuroanatomical and neurochemical correlates

To assess neurochemical and neuroanatomical correlates of age and spatial learning, aged Sprague-Dawley male rats (20-22 mo) were divided into two groups based on their ability to locate a hidden platform in a Morris water maze. An "old good" group of rats acquired the task as rapidly as young (3-6 mo) animals, whereas an "old poor" group of rats failed to show improvement on subsequent testing days. Age-related changes included (a) a significant decrease in the number of choline acetyltransferase (CHAT) immunoreactive cells in the ventral cell group of the septal complex (28%); (b) a decrease in caudate dopamine levels (-11%); and (c) an increase in 5-HIAA levels in the n. accumbens (+25%) and hippocampus (+18%). Spatial learning related changes in aged rats included: (a) an increase in medial frontal cortex 5-HIAA levels (52%) in the old good learners but not old poor learners with (b) a decrease in medial frontal cortex dopamine levels (-24%) only in the old poor learners group and (c) a decrease in n. accumbens DOPAC (-22%) and HVA (-23%) in the old good learners group only. The present study demonstrates age-related but not spatial learning related decrease in CHAT immunoreactive cells in the ventral cell group of the septal complex. Therefore, either the cholinergic cell loss in the septum is unrelated to the acquisition of spatial learning measured by the Morris water maze, or it is a permissive effect along with specific alterations in forebrain dopaminergic and serotonergic systems, particularly in the medial frontal cortex and n. accumbens. The above findings are consistent with findings seen in Alzheimer's disease where both basal forebrain cholinergic nuclei and cortical projecting brainstem monoamine systems are affected.

Neuropsychiatric development: two case reports about the use of dietary fish oils and/or choline supplementation in children

Choline supplementation has been used with moderate success in subgroups of adult patients with neuropsychiatric and medical problems. The dietary fish oils have also been used in adults with hypercholesterolemia. We report on two young children with multiple neurodevelopmental delays, one who responded to choline and eicosapentaenoic acid, and the other to choline alone. A brief discussion about choline's metabolic pathways and benefits is included.

Effect of a new cognition enhancer, alpha-glycerylphosphorylcholine, on scopolamine-induced amnesia and brain acetylcholine

The present study investigates the effect of the administration of alpha-glycerylphosphorylcholine (alpha-GPC) on scopolamine-induced amnesia and on brain acetylcholine (ACh) levels and release in rats. The results indicate that alpha-GPC, when administered orally, reverses the amnesia caused by scopolamine in passive avoidance. The peak effect is observed using 600 mg/kg IG, 5 h before training. The effect of the drug is long lasting (up 30 h) in accordance with its pharmacokinetic characteristics. Since, alpha-GPC administered IG is cleaved within the gut mucosal cells to glycerophosphate and free choline, it is tempting to speculate that this drug acts by increasing the ACh precursor pool. This view is supported also by the observation that alpha-GPC partially counteracts the decrease of brain ACh levels elicited by scopolamine administration. The effect is observed in the hippocampus and cortex, but not in the striatum. Moreover, in ex vivo experiments, alpha-GPC is able to increase the amount of ACh released by rat hippocampus slices following potassium stimulation.

Multiple effects of tetrahydroaminoacridine on the cholinergic system: biochemical and behavioural aspects

9-Amino-1,2,3,4-tetrahydroaminoacridine (THA) in combination with lecithin has been reported to improve the memory of Alzheimer's disease patients. We have examined some properties of THA in vitro and in vivo so as to define some of the mechanism(s) by which THA might produce its therapeutic effects. In vitro, THA was more potent at inhibiting human plasma cholinesterase (IC50 = 0.03 microM) than human erythrocyte acetylcholinesterase (IC50 = 0.3 microM) and rat brain acetylcholinesterase (IC50 = 0.32 microM). Radioligand binding studies indicated that THA binds reversibly and competitively to primary M1 and M2 human cortical muscarinic receptors with similar affinities. Moreover, THA showed similar affinity for temporal cortices muscarinic receptors from Alzheimer and non-Alzheimer (control) brains. In vivo, subcutaneous administration of THA (1-8 mg/kg body weight) to adult rats (6 months old) produced a dose dependent decrease in general activity compared to saline-treated rats. However, at a concentration of 0.5 mg/kg body weight, the general activity of the rats was increased compared to saline-treated rats. The cognitive function of the THA-treated adult rats (subcutaneously 2 mg/kg body weight) was not significantly improved compared to saline-treated rats. It is concluded that the mechanisms of action of THA on the cholinergic system involve reversible inhibition of cholinesterases and reversible and competitive interaction with muscarinic acetylcholine receptors. These effects might be of therapeutic value in the treatment of Alzheimer's disease.

Tetrahydroaminoacridine-lecithin combination treatment in patients with intermediate-stage Alzheimer's disease. Results of a Canadian double-blind, crossover, multicenter study

We studied the efficacy and safety of oral tetrahydroaminoacridine (THA) combined with lecithin in 52 patients with Alzheimer's disease. The maximal tolerated dose of THA (up to 100 mg per day) was determined during an eight-week titration period, after which the tolerated dose of THA or placebo was given during two sequential randomized periods of treatment lasting eight weeks each. Highly purified lecithin (4.7 g per day) was administered during all phases of the study. Efficacy was expressed in terms of scores on the Mini-Mental State (MMS) test, the modified MMS test, the Hierarchic Dementia Scale, the Rapid Disability Rating Scale-II, and the behavioral scale of Reisberg et al. Safety was assessed by careful clinical monitoring as well as serial measurements of liver aminotransferases. Forty-six patients completed the titration period, and 39 completed the double-blind period, during which only the MMS score showed a small but significant increase (P less than 0.05) after four weeks of treatment with THA. Autonomic side effects of THA were common but mild. Reversible elevations of serum aspartate and alanine aminotransferase levels to three or more times the upper limit of normal occurred in 17 percent of patients; most of the patients affected were women. A liver biopsy performed in one patient showed resolving focal liver-cell necrosis. These studies fail to demonstrate a significant clinical benefit of THA given orally in a maximal dose of 100 mg per day over a period of eight weeks in combination with lecithin.

Progress report on the Canadian Multicentre Trial of tetrahydroaminoacridine with lecithin in Alzheimer's disease

Since the discovery of a significant depletion of acetylcholine in discrete areas of the brain of patients affected by Alzheimer's disease, attempts at symptomatic therapy have concentrated on acetylcholine supplementation, an approach that is based upon the efficacy of dopaminergic supplementation therapy for Parkinson's disease. Choline, then lecithin, used orally, failed to improve symptoms but the hypothesis that long-term choline supplementation might stabilize the course of Alzheimer's disease remains to be tested. Nerve growth factor may also offer that possibility. Bethanechol administered intracerebroventricularly did not help when a fixed dose was used but individual titration of more selective muscarinic agonists may prove more effective. In this article we report that tetrahydroaminoacridine (THA), given together with highly concentrated lecithin, appears to bring improvement in cognition and in functional autonomy using the Mini Mental State and the Rapid Disability Rating Scale-2 respectively, without change in behavior as reflected by the Behave-AD. Double-blind cross-over studies are in progress to establish its efficacy. Improvement in study design and means of assessment of cognition, functional autonomy and behavior have been made possible by these drug trials.

Chronic oral physostigmine without lecithin improves memory in Alzheimer's disease

Sixteen patients with early Alzheimer's disease (AD) completed a 3-month outpatient double-blind parallel trial of oral physostigmine versus placebo. Ten subjects received drug; six received placebo. After a dose-titration phase, each patient was placed on his or her best dose of drug or placebo. Subjects were evaluated with both memory and nonmemory tasks. Seven of the ten drug-treated patients, but none of the six placebo-treated patients, demonstrated improvement on a selective reminding task, a test of verbal memory. Family members reported improvement in six of ten drug-treated patients and none of six placebo-treated individuals. There was a trend toward greater improvement with increasing drug dose. There was no improvement on the nonmemory tests administered. The data indicate that oral physostigmine improves memory but not other areas of cognition.

Differential responsivity of mood, behavior, and cognition to cholinergic agents in elderly neuropsychiatric populations

To evaluate the possible differential responsivity of Alzheimer patients to cholinergic agents, a series of pharmacologic challenge studies in 83 neuropsychiatric patients and controls were performed contrasting a cholinergic antagonist (scopolamine) with two cholinergic agonists (arecoline and nicotine). Alzheimer patients displayed significantly greater behavioral and cognitive responses to central cholinergic blockade at lower scopolamine doses than age-matched controls or elderly depressives. These differential changes could not be explained by group differences in the sedative, physiologic, or pharmacokinetic effects of the drug. In addition, the elderly, age-matched control subjects did reveal a profile of cognitive deficits at the highest dose (0.5 mg), which temporarily mimicked the baseline impairments found in early Alzheimer's disease. Together, these findings with scopolamine suggest an increased sensitivity to cholinergic blockade in Alzheimer's disease and demonstrate the first direct evidence of anticholinergic modelling of dementia in normal elderly subjects. To investigate further the postsynaptic cholinergic responsivity in Alzheimer's disease, patients were studied with arecoline and nicotine. While the cognitive effects of both agents were modest at best, there were significant differences in mood and behavioral responses between arecoline and nicotine in Alzheimer subjects. These behavioral changes occurred at much lower doses in the Alzheimer patients than those required in normal controls, once more supporting the notion of increased behavioral sensitivity to cholinergic agents in Alzheimer's disease. In addition, the differential mood effects between these two cholinergic agonists raise new questions about receptor selectivity in the cholinergic regulation of mood.

Auditory long latency event-related potentials in Alzheimer's disease and multi-infarct dementia

An auditory discrimination paradigm was employed to elicit event-related brain potentials in 13 patients with Alzheimer's disease and 14 patients with multi-infarct dementia. The P300 latency was significantly prolonged in 12 patients with dementia compared with age-matched controls and showed a significant negative correlation with the score of Wechsler Adult Intelligence Scale (WAIS), especially with that of Digit Span subtest. There was no disease specificity. After physostigmine treatment, P300 latency decreased and WAIS score increased in 6 among 10 cases.

Oral tetrahydroaminoacridine in long-term treatment of senile dementia, Alzheimer type

We treated 17 patients who had moderate to severe Alzheimer's disease with oral tetrahydroaminoacridine (THA), a centrally active anticholinesterase, in a three-phase study. In the nonblinded first phase of the study, significant improvement occurred in subjects who received the drug, as compared with their pretreatment status, on the global assessment (P = 0.001), the Orientation Test (P = 0.001), and the more sophisticated Names Learning Test (P = 0.001). During the second phase, the subjects served as their own controls in a double-blind, placebo-controlled, cross-over study in which the order of administration of the drug and placebo was randomly assigned. Among the 14 subjects completing Phase II, THA treatment produced significantly better results than placebo on the global assessment (P = 0.003), the Orientation Test (P = 0.004), the Alzheimer's Deficit Scale (P = 0.003), and the Names Learning Test (P = 0.001). Twelve subjects have entered Phase III, which involves long-term administration of oral THA. The average duration of treatment in these subjects at present is 12.6 months; symptomatic improvements have occurred, and no serious side effects attributable to THA have been observed. These encouraging initial results suggest that THA may be at least temporarily useful in the long-term palliative treatment of patients with Alzheimer's disease. We stress that further observations will be required before a clear assessment of the role of this agent can be made.

The cholinergic neurotransmitter system in human memory and dementia: a review

The present paper reviews three types of evidence implicating the role of acetylcholine in human memory and dementia: (1) neuropathological evidence that the cholinergic transmitter system is depleted in Alzheimer-type dementia; (2) psychopharmacological studies that have employed “cholinergic blockade” as a model of cholinergic depletion; and (3) clinical studies of cholinergic “replacement” therapy in Alzheimer-type dementia. The evidence that the cholinergic system is depleted in Alzheimer-type dementia has been complemented by the finding that cholinergic blockade in healthy subjects causes a substantial learning (or “acquisition”) deficit in episodic memory. The overall results of studies of replacement therapy have generally been disappointing, but a few have reported benefits in recall and recognition tests. The role of the cholinergic system in many aspects of memory remains to be elucidated; but it seems unlikely that cholinergic depletion accounts for all aspects of the memory disorder in Alzheimer-type dementia, and possibly the depletions of other neurotransmitters also contribute to the memory impairment.

Transmitter-replacement therapy in Alzheimer's disease using intracerebroventricular infusions of receptor agonists

Neurotransmitter replacement therapy in Alzheimer's Disease is currently being attempted using bethanechol chloride (Urecholine) infused intracerebroventricularly with an Infusaid continuous infusion pump. The rationale of this therapy is based on the severe cortical pre-synaptic cholinergic deficit in the presence of relatively normal post-synaptic muscarinic receptor density. Patients are selected on the basis of strict clinical criteria at a functional stage 4 or 5 of Reisberg. A cortical biopsy at the time of pump and catheter implantation confirms the diagnosis by histological and biochemical examination. Pre-operative, post-operative and serial mental status assessments combined with functional ADL assessments monitor changes in behavior. A 6 months double-blind treatment period is done in every patient, who is then free to continue if he has improved on active treatment. This specific study is part of a multi-centre trial. Other therapeutic trials using somatostatin analogs, such as Sandostatin, could then be done. The biological effects of the latter compound are being studied currently in adult Green Vervet monkeys, prior to its use in Alzheimer patients. Furthermore autoradiography of bethanechol and peptides labeled with 14C administered in these animals by intracerebroventricular infusion will allow a better knowledge of their pharmacological site of action.

Pharmacologic modelling of Alzheimer's disease

Evidence pointing to the central role of the cholinergic system in normal human memory function and disorders such as Alzheimer's disease has grown tremendously in recent years. Anticholinergic and non-cholinergic agents have been found to create transient memory impairments in young adults which mimic the changes associated with normal aging or amnesia. The rationale for using scopolamine, a centrally active anticholinergic agent, as a pharmacologic probe of memory function is reviewed using data from studies in animals and humans. The cognitive functioning of normal elderly controls given scopolamine is compared to the baseline functioning of patients with Alzheimer's disease, followed by a discussion of the use of scopolamine as a modelling agent for dementia.

The neuropathology of Alzheimer's disease: a review with pathogenetic, aetiological and therapeutic considerations

The neuropathology of Alzheimer's disease is reviewed in this paper emphasizing the morphological and morphometric changes that occur in the disease and their relationship to age and ageing. From this, a new hypothesis of pathogenesis is presented which accounts for the pattern of neuronal damage in Alzheimer's disease. This is that the pathogenesis of Alzheimer's disease begins with a leakage of a neurotoxin through a defective cortical blood brain barrier. This incites development of the senile plaque and later, via a retrograde transport of the same (or different) factors, intracellular neurofibrillary tangle formation and death of neurones within areas of cortex affected by plaques and in subcortical areas such as nucleus basalis of Meynert, locus caeruleus and dorsal raphe nuclei, all of which project to these same areas of cortex. Evidence consistent with this hypothesis is presented and the aetiological and therapeutic implications are discussed.

A double-blind, placebo controlled trial of high-dose lecithin in Alzheimer's disease

The first long-term double-blind placebo controlled trial of high dose lecithin in senile dementia of the Alzheimer type is reported. Fifty one subjects were given 20-25 g/day of purified soya lecithin (containing 90% phosphatidyl plus lysophosphatidyl choline) for six months and followed up for at least a further six months. Plasma choline levels were monitored throughout the treatment period. There were no differences between the placebo group and the lecithin group but there was an improvement in a subgroup of relatively poor compliers. These were older and had intermediate levels of plasma choline. It is suggested that the effects of lecithin are complex but that there may be a "therapeutic window" for the effects of lecithin in the condition and that this may be more evident in older patients.

Alzheimer's disease: clinical features, pathogenesis, and treatment

Alzheimer's disease is an insidious degenerative disease of the brain and is the leading cause of dementia in the U.S. Numerous etiologies have been postulated, including a large body of evidence suggesting a slow viral infection, possibly in genetically predisposed individuals, but this remains to be proven. Differential diagnosis is based primarily on exclusion of other treatable forms of dementia. Neurochemical studies suggest a cholinergic deficit; thus primary emphasis in treatment has been directed at enhancing cholinergic activity. Choline and lecithin supplementation generally has been ineffective. Results with physostigmine are encouraging and further studies with this drug prototype are needed. Physostigmine's clinical usefulness is limited, however, due to peripheral side effects and its short duration of action. Other pharmacological approaches, such as naloxone, neural metabolic enhancers, stimulants, and vasopressin analogs, have been investigated. The clinical features and pathology of the disease are reviewed.

Evidence for high affinity choline transport in synaptosomes prepared from hippocampus and neocortex of patients with Alzheimer's disease

Sodium-dependent, hemicholinium-sensitive choline transport was measured in purified synaptosomes prepared from fresh necropsy brain of patients with senile dementia of the Alzheimer type and from control subjects. Choline transport velocity was standardized in terms of the occluded lactate dehydrogenase activity of the various synaptosomal preparations, rather than in terms of the protein content, since this enzyme is more representative of the synaptosome content of the purified homogenates. A regional difference in high-affinity choline transport was observed in purified synaptosomes prepared from brains of mentally normal controls; the velocities of sodium-dependent and hemicholinium-sensitive choline uptake into synaptosomes from hippocampus were about twice as great as that into synaptosomes from frontal cortex, indicating a greater relative density of cholinergic innervation in the hippocampus. Hippocampal and neocortical cholinergic nerve cell endings, prepared as synaptosomes, from brains of patients with Alzheimer's disease, also accumulated choline by a high-affinity mechanism; however, the velocity of uptake into both brain areas was decreased in comparison with controls. Choline transport into synaptosomes from Alzheimer frontal cortex was reduced approximately 50%, while uptake into Alzheimer hippocampal synaptosomes represented only 20% of the control activity. The reduction in synaptosomal high-affinity choline transport in Alzheimer's disease could be indicative of degeneration of cholinergic nerve terminal boutons resulting from cholinergic nerve cell death, or could result from an overall decrease in the number of carrier sites per nerve terminal or in the carrier transport velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral physostigmine and lecithin improve memory in Alzheimer disease

Eight patients with early Alzheimer disease were treated with gradually increasing multiple daily doses of oral physostigmine and supplemental lecithin. Six individuals showed improvement in total recall and retrieval from long-term storage (LTR), with a decrease in intrusions (a measure of inaccurate recall). The optimal individual dose was either 2.0 or 2.5 mg of physostigmine for each responding patient. Results of this open trial were subsequently replicated during a double-blind crossover trial comparing physostigmine treatment to placebo. All six patients again demonstrated improvement in total recall and LTR, with a decrease in intrusions. The decrease in intrusions was strongly correlated with increasing inhibition of cholinesterase activity in cerebrospinal fluid, suggesting that the degree of improvement in the patient's memory was related to the amount of physostigmine that reached the brain. Other neurotransmitters and metabolites in cerebrospinal fluid were unaffected by the physostigmine therapy, suggesting a specific effect of physostigmine on the cholinergic system. The results suggest that small oral doses of physostigmine combined with lecithin ingestion have therapeutic benefit for some patients with Alzheimer disease.

Neurotransmitter deficits in Alzheimer's disease: criteria for significance

A series of histopathologic, morphologic, and pharmacologic criteria are proposed to establish the significance of neurochemical deficits in Alzheimer's disease. The underlying pathogenic biochemistry of a better understood neurotransmitter-deficiency syndrome, Parkinson's disease, validates these criteria. The major neurotransmitter systems are evaluated against these guidelines. Only the cholinergic system fulfills all the criteria. Noradrenergic mechanisms are also implicated. Subsequent neurochemical abnormalities found in the brains of patients with Alzheimer's disease can be evaluated against these criteria.

Presynaptic cholinergic dysfunction in patients with dementia

Indices of presynaptic cholinergic nerve endings were assayed in neocortical biopsy samples from patients with presenile dementia. For those patients in whom Alzheimer's disease was histologically confirmed, [14C]acetylcholine synthesis, choline acetyltransferase activity and choline uptake were all found to be markedly reduced (at least 40%) below mean control values. The changes occurred in samples from both the frontal and temporal lobes and for [14C]acetylcholine synthesis the decrease was similar under conditions of high and low neuronal activity (as assessed by incubations in 31 mM and 5 mM K+ respectively). Samples from other demented patients, in whom the histological features of Alzheimer's disease were not detected, produced values for all three biochemical parameters which were similar to controls. For the total group of patients with presenile dementia there were correlations between values for the three markers of presynaptic cholinergic nerve endings suggestive of a loss of functional activity at these sites in Alzheimer's disease.

Facial recognition memory in dementia

Previous investigations of memory in senile dementia of the Alzheimer's type (SDAT) have focused on verbal learning and memory. The aim of the present study was to determine whether the amnesia of SDAT is limited to verbal material. Patients with SDAT (N = 29; mean age = 69.3) and healthy normal controls (N = 41; mean age = 69.3) were given a test of facial perception and two recognition memory tasks, one for words and one for faces. The results indicate that dementia patients show a deficit in the retention of facial information. This deficit cannot be attributed to faculty initial perception or to a response bias. The verbal and facial memory deficits in SDAT appear to differ: performance on tests of verbal and facial memory is relatively independent, and substantial encoding and linguistic defects contribute to the verbal, but not the facial, memory disorder resulting in more severe impairment on tests of verbal memory. The implications of these findings for research on the neuropharmacology and pathophysiology of SDAT are discussed.

Lecithin treatment of cognitively impaired Parkinson's patients

To test the effects of lecithin on cognitive deficits associated with Parkinson's disease, sixteen elderly and mentally-impaired outpatients with Parkinson's disease participated in a 9-week double-blind placebo-controlled study. Each patient took a daily dose of approximately 32 g of a commercial lecithin preparation containing 25% phosphatidylcholine, or an equivalent amount of powdered skim milk placebo. Marked clinical improvement was not observed, but some indications of a positive treatment effect were obtained on memory, cognition, and motility tests.

The noradrenergic system in Alzheimer and multi-infarct dementias

The number of melanin containing nerve cells of the locus coeruleus and vagus nucleus is reduced in Alzheimer's disease by 60% with decrease of 22% in the protein synthetic capability of remaining cells. These changes are matched by reductions in brain noradrenaline in eight regions, averaging 36%. In multi-infarct dementia, however, all three of these features are unchanged. These findings indicate that degeneration of central noradrenergic nerve cells is a specific aspect of the pathogenic process underlying Alzheimer's disease.

Acetylcholinesterase activities in cerebrospinal fluid of patients with senile dementia of Alzheimer type

We have studied, as a possible marker of cholinergic neurons, the acetylcholinesterase (AChE) activity in cerebrospinal fluid (CSF) of 21 SDA patients and 9 controls of similar age with no neurological disease. The AChE activities were significantly lower in the SDA patients compared to the controls. The AChE activities were also lowered in the most severely demented patients compared to those who were less severely demented but the difference was not statistically significant. As a potential glia marker, beta-glucuronidase activity in CSF was studied, but no significant difference was found in the activities of the SDA patients compared to the controls. The reduced AChE activities in the CSF of the SDA patients may be related to the loss of cholinergic neurons or disturbed cholinergic metabolism in the brain.

Choline chloride fails to improve cognition of Alzheimer's disease

Seven mildly to moderately demented patients with Alzheimer's disease were treated with either placebo or choline chloride (50, 100 and 200 mg/kg/24 hrs) in a double blind, crossover study. Detailed psychometric analysis was carried out at the end of each two-week period of drug or placebo administration. No subjects showed significant overall improvement at any dose level despite more than a doubling of the baseline plasma choline level.