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

Hormesis and medicine

Evidence is presented which supports the conclusion that the hormetic dose-response model is the most common and fundamental in the biological and biomedical sciences, being highly generalizable across biological model, endpoint measured and chemical class and physical agent. The paper provides a broad spectrum of applications of the hormesis concept for clinical medicine including anxiety, seizure, memory, stroke, cancer chemotherapy, dermatological processes such as hair growth, osteoporosis, ocular diseases, including retinal detachment, statin effects on cardiovascular function and tumour development, benign prostate enlargement, male sexual behaviours/dysfunctions, and prion diseases.

Alzheimer's disease drugs: an application of the hormetic dose-response model

This article provides an evaluation of the dose-response features of drugs that are intended to improve memory, some of which have been used in the treatment of Alzheimer's disease (AD). A common feature of these drugs is that they act via an inverted U-shaped dose response, consistent with the hormetic dose response model. This article assesses historical foundations that lead to the development of AD drugs, their dose-response features and how the quantitative features of such dose responses affected drug discovery and development, and the successes and possible failures of such agents in preclinical and clinical settings. This story begins about 150 years ago with the discovery of an active agent in the Calabar bean plant called physostigmine, its unfolding medical applications, and its implications for dose-response relationships, memory enhancement, and improved drug discovery activities. The article also demonstrates the occurrence of U-shaped dose responses for memory with numerous endogenous agonists including neurosteroids, various peptides (e.g., vasopressin, CCK-8, neuropeptide Y), and other agents (e.g., epinephrine, antagonists for platelet activity factor and nicotinic receptors), supporting the generalizability of the hormetic biphasic dose response. Finally, the significance of the U-shaped dose response is critical for successful clinical application, since it defines the therapeutic window.

Effects of chronic administration of huperzine A on memory in guinea pigs

Effects of subchronic administration of huperzine A, a cholinesterase inhibitor, on spatial memory were studied in guinea pig. Spatial memory was appreciated by the Morris water maze test. At a dose of 0.25 microgram/h, inhibiting 36% of blood AChE and 14-20% of central AChE, no effect on spatial learning was found. At a dose of 1 microgram/h, inhibiting 20% of blood AChE and 14-20% of central AChE, no memory impairment was found, on the other hand, a memory enhancing effect, limited to the first day was shown. It thus appears that subchronic administration of huperzine A did not induce deleterious effects on spatial memory.

Cholinergic influences on use-dependent plasticity

Motor practice elicits use-dependent plasticity in humans as well as in animals. Given the influence of cholinergic neurotransmission on learning and memory processes, we evaluated the effects of scopolamine (a muscarinic receptor antagonist) on use-dependent plasticity and corticomotor excitability in a double-blind placebo-controlled randomized design study. Use-dependent plasticity was substantially attenuated by scopolamine in the absence of global changes in corticomotor excitability. These results identify a facilitatory role for cholinergic influences in use-dependent plasticity in the human motor system.

Prophylaxis against organophosphate poisoning by sustained release of scopolamine and physostigmine

Protection efficacy of continuous prophylactic administration of physostigmine and scopolamine against sarin-induced toxicity was evaluated previously in guinea pigs. The present study in large animals used Beagle dogs, that serve as an animal model with cholinergic sensitivity similar to that of humans. Pretreatment with physostigmine salicylate and scopolamine hydrochloride at dose rates of 2.5 and 1 microg x kg(-1) x h(-1), respectively, was administered via Alzet mini-osmotic pumps. At the time of exposure, the physostigmine salicylate concentration in plasma was 0.7 ng x ml(-1) and the scopolamine hydrochloride concentration was ca. 0.2 ng x ml(-1), both of which are levels known to be well tolerated in humans. Whole-blood cholinesterase inhibition was 15-20%. This regimen conferred full protection against 2.5 x LD50 i.v. of sarin. Albeit the high-dose exposure, cholinergic toxicity symptoms were mild with no convulsions. About 11-14 min following poisoning the treated animals started to walk and 15-20 min following exposure full recovery was observed and the dogs behaved normally. With higher dose rates of physostigmine salicylate and scopolamine hydrochloride, at plasma concentrations of 2.1 and 0.6 ng x ml(-1), respectively, treated dogs regained normal posture 6-10 min after exposure.

Physostigmine for Alzheimer's disease

BACKGROUND

The main pharmacological approach for the treatment of Alzheimer's disease (AD) has been based on the use of agents potentiating cholinergic transmission, particularly by inhibiting acetylcholinesterase (AChE), the enzyme that destroys acetylcholine after it has been secreted into the synaptic clefts. Physostigmine is an AChE inhibitor originally extracted from calabar beans. It is licensed in many countries as an agent for reversing the effect of drugs and poisons causing the anticholinergic syndrome. Studies conducted more than 20 years ago suggested that physostigmine could improve memory in people with or without dementia. Investigation of this property has been limited by the very short half-life of physostigmine. Various forms of administering the drug have been tried to overcome this problem, most recently a controlled-release (CR) oral formulation, and a skin patch. It has been proposed as a potential drug for the symptomatic treatment of AD.

OBJECTIVES

To determine whether there is evidence of beneficial effects for the use of physostigmine in Alzheimer's disease. To assess the incidence and severity of adverse effects.

SEARCH STRATEGY

The Cochrane Controlled Trials Register was searched using the following terms: 'physostigmine', 'physostigmine salicylate', 'Synapton' and 'Antilirium' in accordance with the Cochrane Dementia and Cognitive Improvement Group's search strategy. The pharmaceutical company was contacted.

SELECTION CRITERIA

All relevant unconfounded, double-blind, randomized, placebo-controlled trials in which physostigmine was administered for more than one day to patients with dementia of Alzheimer type. Trials in which the allocation to the treatment was not randomized, or in which the allocation to the treatment was not concealed were excluded.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two reviewers (JMC & JB), pooled where appropriate and possible, and the weighted or standardized mean differences or Peto odds ratios (95% CI) were estimated. Where possible, intention-to-treat analysis was used.

MAIN RESULTS

Fifteen studies were included using four different methods of administration of physostigmine. Four studies, involving 29 people in total, used intravenous infusion; seven, involving 131 people, used a conventional oral form; four, involving 1456 participants, used a controlled-release oral form, and one study of 181 people used a verum skin patch. There are no usable results from the intravenous infusion trials, and the few results from the conventional oral form showed no benefit of physostigmine compared with placebo. The results from two of the four studies of the controlled-release physostigmine apply only to a group of patients identified as responders in a pre-randomization titration period. The best dose physostigmine (mean 25mg/day) was associated with a 1.75 point improvement on ADAS-Cog score (mean difference -1.75, 95% confidence interval -2.90, -0.60 on an intention-to-treat basis) and a 0.26 point improvement on the CGIC score (treated as a continuous scale) (mean difference -0.26, 95% confidence interval 0.06, 0.46 on an intention-to-treat basis) compared with placebo at 6 weeks. There were statistically significantly higher numbers of patients from the physostigmine group withdrawing from the trial (22/183 vs 2/183)(OR 5.92, 95% confidence limits 2.59, 13.54) and suffering at least one event of nausea, vomiting, diarhoea, anorexia, dizziness, stomach pain, flatulence or sweating compared with placebo at 6 weeks. The best dose physostigmine (mean 27mg/day) was associated with a 2.0 point improvement on ADAS-Cog score (mean difference -2.02, 95% confidence interval -3.59, -0.45 on an intention to treat basis) compared with placebo at 12 weeks. There were statistically significantly higher numbers of patients from the physostigmine group withdrawing from the trial due to adverse events (13/83 vs 5/93)(OR 3.05, 95% confidence limits 1.15, 8.07) and suffering at least one event of nausea, vomiting, diarhoea, anorexia, dizziness, stomach pain, tremor, asthenia or sweating compared with placebo at 12 weeks. When no attempt was made to identify responders and all relevant patients with Alzheimer's disease were randomized, fixed dose physostigmine (mean 33 mg/day) was associated with a statistically significantly higher number withdrawing (234/358 vs 31/117)(OR 4.82, 95% confidence limits 3.17, 7.33), withdrawing due to adverse events (196/358 vs 10/117) (OR 6.54, 95%confidence limits 4.29, 9.95) and suffering at least one event of nausea, vomiting, diarhoea, anorexia, dizziness, stomach pain, dyspepsia, sweating, asthenia, dyspnoea or abnormal dreaming compared with placebo at 24 weeks. The results from the study of the verum patch physostigmine show that the double dose (delivering mean dose 12mg/day) was associated with statistically significantly higher numbers suffering at least one adverse event of vomiting, nausea or abdominal cramps compared with placebo at 24 weeks, but placebo was associated with statistically significantly greater numbers of gastrointestinal complaints at 24 weeks compared with single-dose physostigmine.

REVIEWERS' CONCLUSIONS

The evidence of effectiveness of physostigmine for the symptomatic treatment of Alzheimer's disease is limited. Even in a controlled release formulation designed to overcome the short half-life, physostigmine showed no convincing benefit and adverse effects remained common leading to a high rate of withdrawal.

Preferential cerebrospinal fluid acetylcholinesterase inhibition by rivastigmine in humans

This study sought to examine the feasibility of prolonged assessment of acetylcholinesterase (AChE) activity in the cerebrospinal fluid (CSF) of volunteers and to test the hypothesis that rivastigmine (ENA-713; Exelon, Novartis Pharma AG, Basel, Switzerland) selectively inhibits AChE in CSF in humans at a dose producing minimal inhibition of the peripheral enzyme. Lumbar CSF samples were collected continuously (0.1 mL x min(-1)) for 49 hours from eight healthy volunteers who took either placebo or a single oral dose of rivastigmine (3 mg). CSF specimens and samples of blood cells and blood plasma were analyzed at intervals for rivastigmine and its metabolite NAP 226-90 ([-] [3-([1-dimethylaminolethyl)-phenol]), erythrocyte AChE activity, CSF AChE activity, and plasma and CSF butyrylcholinesterase (BuChE) activity. Safety evaluations were performed 23 hours after drug dosing and at the end of the study. Evaluable data were obtained from six subjects. The mean time to maximal rivastigmine plasma concentration (tmax) was 0.83 +/- 0.26 hours, the mean maximal plasma concentration (Cmax) was 4.88 +/- 3.82 ng x mL(-1), the mean plasma area under the concentration versus time curve (AUC0-infinity) was 7.43 +/- 4.74 ng x hr x mL(-1), and the mean plasma t1/2 was 0.85 +/- 0.115 hours. The concentration of rivastigmine in CSF was lower than the quantification limit for assay (0.65 ng x mL(-1)), but NAP 226-90 reached a mean Cmax of 3.14 +/- 0.57 ng x mL(-1). Only minimal inhibition of erythrocyte AChE activity (approximately 3%) was observed. Inhibition of AChE in the CSF after rivastigmine administration was significantly greater than after placebo for up to 8.4 hours after the dose and was maximal (40%) at 2.4 hours. Plasma BuChE activity was significantly lower after rivastigmine than after placebo, but this was not clinically relevant. BuChE activity in CSF was significantly lower after rivastigmine than after placebo for up to 3.6 hours after dosing, but this difference was not sustained. This study confirms the feasibility of using continuous measurement of AChE activity in CSF over prolonged periods, that rivastigmine markedly inhibits CSF AChE after a single oral dose of 3 mg, and that the inhibition of central AChE is substantially greater than that of peripheral AChE or BuChE.

A phase II study in patients with Alzheimer's disease to assess the preliminary efficacy and maximum tolerated dose of rivastigmine (Exelon)

Rivastigmine is a carbamate acetylcholinesterase (AChE) inhibitor with central selectivity. Early studies showed that daily doses up to 6 mg/day have some efficacy in patients with dementia of the Alzheimer type (DAT). The present study was designed to assess the safety, tolerability and efficacy of rivastigmine at doses up to 12 mg/day. A total of 114 patients with mild-moderate DAT were randomly assigned to either rivastigmine (b.i.d. (twice daily) or t.i.d. (three times daily)) or placebo in a double-blind fashion titrated to their maximum tolerated dose over 10 weeks followed by an eight-week maintenance phase. The mean maximum tolerated dose was approximately 10 mg/day (b.i.d. or t.i.d.). Gastrointestinal complaints, the majority of which were mild to moderate, were the most frequently reported adverse events. No clinically relevant changes in vital signs, haematology or organ function were detected. Significantly more patients taking rivastigmine b.i.d. were considered improved according to the Clinicians' Interview-Based Impression of Change-Plus (CIBIC-Plus) vs. placebo (57% vs. 16%, respectively; P = 0.027). The Nurses' Observation Scale for Geriatric Patients (NOSGER) (memory component) and the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) also improved in the rivastigmine b.i.d. group vs. placebo (mean change from baseline on NOSGER = -0.7 vs. +1.3, respectively; P = 0.037: mean change from baseline on ADAS-cog = -2.7 vs. +0.2, respectively; P = 0.054). Despite the relatively small size and limited duration of the study, the finding that rivastigmine induced changes in the same (positive) direction in all three dimensions measured suggests that rivastigmine at doses of up to 12 mg/day has useful efficacy in patients with mild-moderate DAT. Reports from larger phase III studies confirm this finding. The results of this study also suggest that b.i.d. is the more efficacious regimen and has comparable tolerability to the t.i.d. regimen.

Cholinesterase inhibitors: a therapeutic strategy for Alzheimer disease

OBJECTIVE

To provide a review of acetylcholinesterase inhibitors (AChEIs) tested as therapeutic agents for Alzheimer disease (AD).

DATA SOURCES

MEDLINE searches (January 1986-July 1998) identified pertinent literature. Selected references from these articles, as well as abstracts from recent meetings and package insert literature from approved compounds, were also used as source material.

DATA EXTRACTION

AChEIs were reviewed with regard to chemical structure, mechanism of inhibition, substrate specificity, pharmacokinetics/pharmacodynamics, safety/tolerability, and efficacy.

DATA SYNTHESIS

Cholinergic deficits, leading to cognitive impairment, are a significant aspect of neurodegeneration in AD. AChEIs reduce the degradation of acetylcholine, thus enhancing cholinergic transmission. In addition to the two agents approved by the Food and Drug Administration, tacrine and donepezil, six other compounds of diverse chemical structure and mechanism of inhibition including physostigmine, metrifonate, rivastigmine, and galantamine are under investigation as potential therapy for AD. These compounds are structurally diverse, possess unique patterns of specificities for the various forms of cholinesterase enzymes, use distinct mechanisms of enzyme inhibition, present unique adverse event profiles, and offer relatively similar mean gains in cognitive abilities to patients with AD in controlled clinical trials.

CONCLUSIONS

Relative to placebo, new AChEIs in development provide modest improvements in cognition for patients with mild to moderate AD, with improved tolerability profiles and more convenient dosing relative to tacrine. The availability of a wide array of AChEIs soon to be accessible to patients with AD will provide additional options to those who cannot tolerate or do not respond to drugs currently used for AD.

Pharmacological modulation of Alzheimer's beta-amyloid precursor protein levels in the CSF of rats with forebrain cholinergic system lesions

Abnormal deposition and accumulation of Alzheimer's amyloid beta-protein (A beta) and degeneration of forebrain cholinergic neurons are among the principal features of Alzheimer's disease. Studies in rat model systems have shown that forebrain cholinergic deficits are accompanied by induction of cortical beta-amyloid precursor protein (beta-APP) mRNAs and increased levels of secreted beta-APP in the CSF. The studies reported here determined whether the CSF levels of secreted beta-APP could be altered pharmacologically. In different experiments, rats with lesions of the forebrain cholinergic system received injections of vehicle, a muscarinic receptor antagonist scopolamine, or one of two cholinesterase inhibitors - diisopropyl phosphorofluoridate (DFP) or phenserine. Scopolamine was administered to determine whether the levels of beta-APP in the CSF could be increased by anticholinergic agents. The cholinesterase inhibitors were administered to determine whether the forebrain cholinergic system lesion-induced increases in CSF beta-APP could be reduced by cholinergic augmentation. Scopolamine administration led to a significant increase in the CSF levels of secreted beta-APP in sham-lesioned rats. Phenserine, a novel, reversible acetyl-selective cholinesterase inhibitor, significantly decreased the levels of secreted beta-APP in the CSF of forebrain cholinergic system-lesioned rats whereas DFP, a relatively non-specific cholinesterase inhibitor, failed to affect CSF levels of secreted beta-APP. These results suggest that the levels of secreted beta-APP in the CSF can be pharmacologically modulated but that this modulation is dependent upon the status of the forebrain cholinergic system and the pharmacological properties of the drugs used to influence it.

Assessment of motor and process skills as a measure of IADL functioning in pharmacologic studies of people with Alzheimer's disease: a pilot study

The purpose of this pilot study was to evaluate the usefulness of the Assessment of Motor and Process Skills (AMPS) as an outcome measure of instrumental activities of daily living (IADL) in pharmacologic studies of people with Alzheimer's disease. The AMPS simultaneously measures motor and process skills and their effect on the ability of the person to perform familiar IADL tasks. We administered the AMPS to 11 Alzheimer inpatients in a 3 1/2-month, double-blind, placebo-controlled, crossover study of fluoxetine and selegiline administered as single agents and in combination with physostigmine. Results indicated that there was a significant difference in IADL ability among study conditions for process skills, but not for motor skills, thereby suggesting that the AMPS is useful as a sensitive outcome measure of IADL ability in drug trials with this population.

The use of animal models to study the effects of aging on cognition

This review addresses the importance of animal models for understanding the effects of normal aging on the brain and cognitive functions. First, studies of laboratory animals can help to distinguish between healthy aging and pathological conditions that may contribute to cognitive decline late in life. Second, research on individual differences in aging, a theme of interest in studies of elderly human beings, can be advanced by the experimental control afforded in the use of animal models. The review offers a neuropsychological framework to compare the effects of aging in human beings, monkeys, and rodents. We consider aging in relation to the role of the medial temporal lobe in memory, the information processing functions of the prefrontal cortex in the strategic use of memory, and the regulation of attention by distributed neural circuitry. We also provide an overview of the neurobiological effects of aging that may account for alterations in psychological functions.

Relationship between pharmacodynamic activity and cognitive effects of eptastigmine in patients with Alzheimer's disease. Eptastigmine Study Group

OBJECTIVE

To assess the safety, tolerability, pharmacodynamics, and preliminary efficacy of eptastigmine, a new long-acting cholinesterase inhibitor, in patients with probable Alzheimer's disease.

METHODS

This was a double-blind, randomized, placebo-controlled, unbalanced parallel-group study. One-hundred and three patients (83 in the eptastigmine group and 20 in the placebo group) were recruited by 10 centers. Patients received 20 mg eptastigmine or placebo for 4 weeks with twice-a-day or three-times-a-day regimens, depending on body weight (< or = 65 kg or > 65 kg, respectively). Patient performance on the Logical Memory Test, Semantic Word Fluency Test, Trail Making Test, Index of Independence in Activities of Daily Living, Instrumental Activities of Daily Living Scales (IADL), and the Physician and Caregiver Clinical Global Impression of Change (CGIC) was assessed at baseline and at the end of treatment.

RESULTS

Nine patients, all from the eptastigmine group, did not complete treatment because of uncooperativeness (n = 3), adverse events (n = 3), protocol violations (n = 2), and clinical decline (n = 1). Twenty-five patients receiving eptastigmine (34%) reported adverse events mainly of the cholinergic type. Cholinergic side effects were generally associated with peak red blood cell cholinesterase inhibition exceeding 50% after the first dose, or 70% at steady state. At steady state, average daily acetylcholinesterase inhibition ranged from 13% to 54%. Overall, 34% of patients receiving eptastigmine versus 0% receiving placebo (p = 0.006) improved on the Physician CGIC. This percentage increased to 46% in the subgroup of patients with average daily acetylcholinesterase inhibition ranging from 30% to 35%. Patient performance on the IADL also improved significantly compared with the placebo group (p = 0.019). In the eptastigmine group, performances on all tests and scales improved with an inverted U-shaped relation to average daily acetylcholinesterase inhibition.

CONCLUSIONS

This study shows that doses of 40 to 60 mg per day of eptastigmine are relatively safe and well tolerated and that moderate acetylcholinesterase inhibition is associated with maximal cognitive efficacy.

Clinical pharmacokinetics of physostigmine in patients with Alzheimer's disease

OBJECTIVE

To study the pharmacokinetic and pharmacodynamic properties of physostigmine in subjects with Alzheimer's disease.

METHODS

Plasma physostigmine concentration and butyrylcholinesterase inhibition were measured in blood samples collected during and after a single high-dose (1 to 1.5 mg for 45 to 60 minutes) and a sustained low-dose steady-state intravenous infusion in nine subjects with Alzheimer's disease. Escalating doses (0.5 to 25 mg/day) were administered during a 2-week period. A dose (2 to 12 mg/day) that optimized cognition in each subject was identified and then administered in a randomized, double-blind, placebo-controlled crossover design for 1 week.

RESULTS

The elimination half-life of physostigmine was 16.4 +/- 3.2 (SE) minutes. Clearance and volume of distribution were 7.7 +/- 0.9 (SE) L/min and 2.4 +/- 0.6 (SE) L/kg, respectively. Butyrylcholinesterase inhibition half-life was 83.7 +/- 5.2 (SE) minutes. During sustained steady-state infusion, plasma physostigmine concentration (r = 0.95) and butyrylcholinesterase inhibition (r = 0.99) were linearly correlated with the dose. In five cognitive responders, the memory enhancement was significantly correlated (r = 0.86; p < 0.05) with butyrylcholinesterase inhibition.

CONCLUSIONS

These results showed that, in cognitive responders, memory enhancement by physostigmine in Alzheimer's disease is correlated directly to the magnitude of plasma cholinesterase inhibition. Furthermore, during single-dose conditions, the dynamic half-life is five-fold longer than the kinetic half-life.

Prophylactic transdermal treatment with physostigmine and scopolamine against soman intoxication in guinea-pigs

This study was designed to evaluate the prophylactic efficacy of transdermally administered physostigmine (PHY) against soman exposure using guinea-pigs. Transdermal PHY pad (3 cm2 kg-1; 60 micrograms cm-2), containing a vehicle based on propionic acid, was applied onto the dorsal back of the animals, 24 h before exposure to the organophosphate. At the time of exposure, PHY concentrations in brain and plasma were ca. 3.6 ng g-1 and 4.1 ng ml-1, respectively. Brain and whole blood cholinesterase (ChE) activity was inhibited to 70% and 47% of the original activity, respectively. Transdermal PHY by itself protected up to 70% of the animals exposed to 1.5 LD50 of soman (100% mortality was recorded in the control group). Combining transdermal PHY with Scopoderm provided full protection against 1.5 LD50 of soman (protection of 70% against 3 LD50). When the prophylactic treatment was combined with post-exposure therapy (atropine, 10 mg kg-1; toxogonin, 10 mg kg-1) 1 min after 5 LD50 of soman, protection of 90% of the animals was achieved.

Pharmacotherapy of cognitive impairment in Alzheimer's disease: a review

Experimental pharmacotherapy of cognitive impairment in Alzheimer's disease has seen a recent proliferation of drug trials involving a wide variety of drugs. Many of the earlier studies focused on cholinergic agents. However, subsequent advances in basic and biological sciences have broadened the scope of therapeutic strategies beyond the neurotransmitter approaches to include neurotrophic, metabolic-enhancing, membrane-modifying, and antitoxic agents, and have also provided rationale for developing antiamyloid and anti-infective therapies. For the clinician, it has not been easy to keep abreast of these developments. In this article, I present an overview of the cognition-enhancing drugs that have been used in the past, of those currently under investigation, and of new drugs and strategies that are likely to receive attention in the next few years.

Research trends in Alzheimer's disease

Alzheimer's disease (AD) is a tragic condition. The individual experiencing the loss of memory, difficulty with language, change in personality, and disturbance in behavior associated with AD is not alone; the number of people with AD is estimated at 4 million; by the year 2050, as many as 14 million Americans may be afflicted (National Institute of Aging, 1992). AD is the fourth leading cause of death for adults, taking more than 100,000 lives annually. The families of these patients also are victims, as they watch their loved ones slowly forget them and all that was once meaningful in their lives.

A screening concept based on a hypothesis led to the development of a putative cognitive enhancer that stimulates penile erection

Starting from the hypothesis that drugs which specifically activate the hippocampal cholinergic nerve activity may ameliorate memory impairments, we carried out a series of evaluations for a novel cognitive enhancer using enhancement of penile erection as a sign of cholinergic activation, and found FR64822. The compound facilitated penile erection in naive rats, and it ameliorated scopolamine-induced amnesia of rats in passive avoidance tasks with bell-shaped dose-response curves, while it dose-dependently reduced body weight gain in Zucker fatty rats. Pretreatment with sulpiride (32 mg/kg, p.o.) hardly affected the former two activities, but significantly reduced the anorectic activity in Zucker rats. Further evaluation of FR64822 derivatives characterized a second compound, FR121196, which induces penile erection and memory enhancement, but not body weight reduction. Memory enhancing and erection stimulating activities of FR121196 were abolished in rats treated with either cysteamine (200 mg/kg, s.c.), a somatostatin depletor, or lesioning of the serotonergic raphe nuclei. Thus, classic whole animal studies based on a hypothesis proved to be efficient for reaching our objective, the discovery of a new drug. They also gave us insight into the common somatostatinergic and serotonergic mechanisms underlying penile erection and memory improvement.

Cholinergic approaches to the treatment of progressive supranuclear palsy

In spite of the severe loss of cholinergic neurons in the brains of patients with progressive supranuclear palsy (PSP), marginal or null benefits are seen in clinical trials after the administration of physostigmine, a cholinesterase inhibitor, or RS-86, a cholinergic agonist. The possible role of cholinergic therapy in PSP is reevaluated.

Antiamnesic and cholinomimetic side-effects of the cholinesterase inhibitors, physostigmine, tacrine and NIK-247 in rats

The effects of physostigmine, tacrine and NIK-247 on scopolamine-induced impairment of a passive avoidance response were examined in rats. In addition, we investigated possible peripheral side-effects: miosis and salivation, and central side-effects: hypothermia and tremor which are mediated by cholinergic activation. Intraperitoneal injection of physostigmine reversed scopolamine-induced amnesia at a dose of 0.03 mg/kg. Antiamnesic effects of oral administration of tacrine and NIK-247 were observed at doses of 0.3 and 0.1-0.3 mg/kg, respectively. Intraperitoneal injection of physostigmine induced miosis, salivation, hypothermia and tremor at doses > or = 0.1, 0.3, 0.3 and 1 mg/kg, respectively. Oral administration of tacrine (at doses > or = 0.3 mg/kg) and NIK-247 (at doses > or = 3 mg/kg) produced miosis. Tacrine (at doses > or = 1 mg/kg) and NIK-247 (at doses > or = 3 mg/kg) produced hypersalivation. Hypothermia and tremor were observed after administration of tacrine (at doses > or = 10 mg/kg) and NIK-247 (30 mg/kg). The antiamnesic dose of physostigmine was 1/30-1/3 of doses with central or peripheral side-effects. The dose ratio of tacrine was 1/30-1; that of NIK-247 was 1/300-1/10. These results indicate that NIK-247 has higher safety and greater selectivity for cognitive functions than physostigmine or tacrine.

Korsakoff's syndrome, cognition and clonidine

Eighteen patients suffering from Alcoholic Korsakoff's Syndrome participated in a placebo-controlled double-blind cross-over trial of clonidine 0.3 mg b.d. for two weeks versus matched placebo for two weeks. A detailed neuropsychological assessment was carried out at the end of each treatment phase and staff ratings of behaviour were also obtained. Clonidine treatment resulted in no significant improvement over placebo on any of the cognitive measures employed. The results contradict previous smaller studies which had suggested that chronic treatment with clonidine had a memory-enhancing effect in Korsakoff's syndrome.

Memory improvement without toxicity during chronic, low dose intravenous arecoline in Alzheimer's disease

Arecoline, a cholinergic agonist, administered at low doses by continuous intravenous infusion for up to 2 weeks, significantly and replicably improved memory in five of nine subjects with mild-moderate Alzheimer's disease. During dose finding, performance on a verbal memory task improved with an inverted U-shaped relation to dose. Six of nine subjects were classified as responders. During blinded, placebo-controlled, individualized optimal dosing for 5 days, verbal memory again improved in five of six responders but not in any non-responder. No adverse drug effects occurred. Arecoline, and possibly other cholinergic agonists, can safely improve memory in Alzheimer's disease at doses much lower than previously studied.

Effect of different subtypes of cognition enhancers on long-term potentiation in the rat dentate gyrus in vivo

The effect of four drugs considered as cognition enhancers on the amplitude of the population spikes and on the long-term potentiation (LTP) evoked by perforant path stimulation was investigated in rat dentate gyrus in vivo. LTP was characterized by the absolute increase in the amplitude of the population spikes, which were expressed in mV, contrary to the widely used percentage value, because the absolute increase was independent of the pretetanus level, whereas the percentage increase was found to be negatively correlated with it. Intravenous administration of the drugs (piracetam 500 mg/kg, hydergine 2 mg/kg, vinpocetine 0.1 and 5 mg/kg and physostigmine 0.01 and 0.1 mg/kg) did not influence the amplitude of the population spikes itself. Piracetam and hydergine did not have an effect on LTP, while vinpocetine and physostigmine altered LTP in a similar manner. The higher doses of the two latter drugs, administered 5 min before tetanic stimulation, induced a significant potentiation of LTP, whereas a significant inhibition of LTP was obtained when the drugs were administered 30 min before tetanic stimulation. Based on the results obtained from guinea pig hippocampal slices, an LTP-potentiating effect of all compounds tested could have been anticipated, but this was not supported by our data. The apparent contradiction between the in vivo and in vitro results is discussed.

CGS 5649 B, a new compound, reverses age-related cognitive dysfunctions in rats

CGS 5649 B improves the learning performance of aged rats in a one-way active-avoidance situation. If, under reversed conditions, treated aged rats are also tested for passive avoidance, they show "place learning," which our findings have demonstrated to be typical of young rats. The effects of the substance are not confined to these experimental models nor are they species specific: it also facilitates passive avoidance in mice and social learning in rats. The compound is effective if administered before or immediately after the learning trial.

Dementia: the neurochemical basis of putative transmitter orientated therapy

The neurotransmitter deficits of dementias, including Alzheimer's dementia, Lewy body dementia and Parkinson's disease are discussed in relation to cognitive and behavioural impairments together with neuropathological changes and available data on the status of receptor transmembrane signalling. Potential therapeutic strategies for dementia are outlined based on the following systems: excitatory amino acids, gamma-amino butyric acid, acetylcholine (muscarinic and nicotinic), noradrenaline, serotonin and peptides. These include the attenuation of transmitter deficits by agonists and agents inhibiting transmitter breakdown and support for surviving neurons by suppression of inhibitory inputs, trophic factors and neural implantation.

Differential effects of physostigmine and pilocarpine on the spatial memory deficits produced by two septo-hippocampal deafferentations in rats

Rats that had received two kinds of septo-hippocampal deafferentations, medial septum (MS) lesion and fimbria-fornix (FF) transection, were assayed for brain cholineacetyltransferase (ChAT) activity and spatial memory in an 8-arm radial maze task. Both lesions produced profound and long-lasting spatial memory impairments, which were characterized by a reduction in the numbers of correct arm choices and first correct choices, a reduction in the percent of correct choices and an increase in the number of errors. The degree of memory impairment was severer in FF- than in MS-lesioned rats, and paralleled that of decreases in ChAT activity in the hippocampus. MS lesion reduced ChAT activity in the hippocampus by approximately 45%, while FF lesion almost completely depleted the activity. An intraperitoneal injection of physostigmine (0.0032-0.32 mg/kg), an acetylcholinesterase (AChE) inhibitor, significantly ameliorated the spatial memory deficit induced by MS lesion, but hardly affected that by FF lesion. In contrast, intraperitoneal doses (0.032-3.2 mg/kg) of pilocarpine, a muscarinic agonist, showed a significant improvement of both types of memory deficit with bell shaped dose-response curves. The drug was more potent in the FF- than in the MS-lesioned rats. These results suggest that the septo-hippocampal cholinergic system plays a crucial role in the maintenance of spatial memory, and that the degree of septo-hippocampal deafferentation affects the efficacy of cholinergic drugs.

Survival of patients with dementia

The evidence on survival in dementia is summarized. There are no reliable data on survival after onset of dementia or after first contact with medical services. People with dementia in outpatient clinics and nursing homes have 2-year survival rates of 75% (range 60%-95%) and 50% (range 30%-65%), respectively. Differences in survival between patients with senile dementia of the Alzheimer's type (SDAT) and multi infarct dementia (MID) are small. Women in nursing homes have a better prognosis than men (2-year survival rates, 60% vs 40%). Dementia patients have a considerable excess mortality when compared to the vital statistics. There is no evidence for improvement of survival rates during recent decades. Recommendations for future studies are made.

Extraction of physostigmine from biologic fluids and analysis by liquid chromatography with electrochemical detection

A rapid and simple method is described for the extraction of physostigmine (Phy) and its hydrolysis product, eseroline, from plasma, whole blood, and cerebrospinal fluid (CSF) and their subsequent quantitation by high-performance liquid chromatography (HPLC) with dual electrode electrochemical detection. Phy and eseroline were extracted from biologic fluids with cyano-phase columns eluted with 0.1 M citrate buffer, pH 4 containing 20% acetonitrile. Phy recovery from citrate buffer and CSF was nearly 100%. Phy recovery from plasma was 82% when methanol was used to precipitate proteins and 62% when HClO4 was used to precipitate proteins. Phy recovery from whole blood was only 17%. These results are discussed in the context of attempting to measure Phy in fluids of patients receiving this drug in clinical trials for the treatment of Alzheimer's disease.

Tetrahydroaminoacridine improves the spatial acquisition deficit produced by nucleus basalis lesions in rats

We administered tetrahydroaminoacridine (THA), a cholinesterase inhibitor, to rats with bilateral nucleus basalis magnocellularis lesions and measured their performance in a spatial learning task. The subjects, 34 male Fischer-344 rats, received bilateral excitotoxic NBM lesions; 10 other rats served as unlesioned controls. Two weeks later the animals were tested in a circular water maze for time and distance swum to find a submerged platform. We tested three different doses (5.0, 2.5, and 1.25 mg/kg) of daily subcutaneous THA against a lesioned control group receiving saline and a fifth group of untreated unlesioned controls. The saline-treated lesioned group showed a significant impairment of acquisition. The 1.25 mg/kg group performed significantly better than the lesioned controls with respect to latency. Analysis of swim speed data showed slowing in the 2.5 and 5.0 mg/kg groups. Analysis of the distance swum to find the platform, an untimed task that corrects for the difference in swim speeds, showed statistically significant improvement in all three treated groups. Additionally, spatial memory for the platform location was improved by two of the three doses of THA tested. Passive avoidance retention was not impaired by our lesion. All lesioned groups had comparable reductions of cortical choline acetyltransferase. Our data show significantly improved spatial learning with THA. These data provide an additional rationale for further clinical testing of THA and other centrally active cholinergic agents in diseases with cholinergic loss.

Effect of a novel CNS-selective cholinesterase inhibitor, SM-10888, on habituation and passive avoidance responses in mice

The effects of the tacrine (THA) derivative SM-10888 (9-amino-8-fluoro-1,2,3,4-tetrahydro-2,4-methanoacridine citrate) on habituation and passive avoidance responses were studied in mice. We examined its effects on habituation of exploratory activity, measured by photo-cell beam interruptions in a small, simple cage and cycloheximide (CXM)- or electroconvulsive shock (ECS)-induced stepdown type passive avoidance response (PAR) failures in comparison with those of THA, amiridin, HP-029 and physostigmine. SM-10888 (6 mg/kg, p.o.) administered post-acquisition session enhanced the retention of habituation. CXM- and ECS-induced PAR failures were improved by SM-10888 (6 mg/kg, p.o.) administered at pre-training or post-training, respectively. THA enhanced the retention of habituation and improved CXM-induced PAR failure at 30 mg/kg, p.o., but did not affect ECS-induced PAR failure at 1-15 mg/kg, p.o. Amiridin and HP-029 were also effective on habituation and CXM-induced PAR failure at 40-50 mg/kg, p.o., but did not affect ECS-induced PAR failure at the tested doses. Physostigmine showed a moderate improvement only in CXM-induced PAR failure. The results indicate that SM-10888 enhanced habituation and improved PAR failures at much lower doses than THA. This seems to depend on its high selectivity to the central nervous system.

Biological and neuropsychological characterization of physostigmine responders and nonresponders in Alzheimer's disease

To assess the efficacy of oral physostigmine for the treatment of Alzheimer's disease, 20 patients were entered into a clinical trial. All patients underwent a dose-finding phase (two weeks), followed by an open trial (two weeks), and a double-blind crossover phase (two weeks drug, two weeks placebo). Extensive neuropsychological testing (Buschke Selective Reminding procedure, category generation, picture recognition, finger tapping) and measurement of systemic cholinergic parameters were measured during each of these phases. Patients were classified as physostigmine responders and nonresponders based on a priori established criteria. Using these, nine patients were found to respond to physostigmine, while 11 were classified as nonresponders. During baseline conditions, responders when compared to nonresponders were found to have higher concentrations of red blood cell (RBC) choline (Ch) and higher ratios of RBC Ch to plasma Ch. Neuropsychological tests were found to fall into one of three categories. The first group of tests were sensitive to drug effects and differentiated physostigmine responders from nonresponders; the second group was found to predict responsiveness; and the third group was neither predictive nor sensitive to drug effects.

Drug treatments of dementia

Present drug treatments for the more common types of dementia are largely palliative or symptomatic, but the promise of drugs to prevent the development of dementia does not seem unrealistic. Neuropharmacological strategies that aim to improve behavioural or cognitive symptoms in dementia are subdivided into drugs that modify central cholinergic, serotonergic, dopaminergic, GABAnergic, and peptidergic transmission. There are no clear clinical guidelines for the management of demented patients who are also hypertensive. The early identification of patients with incipient dementia, the detection of slight but theoretically important beneficial effects, the optimum method of drug administration, more soundly based treatment of behavioural symptoms, and the evaluation of drug combinations are all identified as areas requiring further research.