Altered guanosine and guanine concentrations in rabbit striatum following increased dopamine turnover

The significance of guanine nucleotides and nucleosides in neurodegenerative disorders is suggested by recent reports that these molecules enhance neurite branching and astrocyte proliferation. The objective of this study was to investigate the influence of increased dopamine metabolism, produced by 5-day treatment of rabbits with reserpine (2 mg/kg) or levodopa (LD) (50 mg/kg), on striatal concentrations of guanosine, guanine, and their metabolites. Reserpine treatment decreased striatal guanosine by 41% and increased guanine by 50%, while LD decreased guanosine by 48% (all p < 0.01 vs. vehicle-treated controls). LD also increased guanine by 22% (not statistically significant). Xanthine and uric acid concentrations were unchanged. Because of the neurotrophic properties of guanosine and guanine, changes in striatal concentrations of these purines secondary to increased dopamine (DA) turnover may have relevance for survival of remaining dopaminergic neurons in Parkinson's disease (PD).

Idiosyncratic adverse reactions to intramuscular botulinum toxin type A injection

Three cases of adverse reactions to repeated intramuscular botulinum toxin A (BTA) injections are described: a persistent rash on the face at the site of injection, a localized anaphylactic reaction following BTA injection into one leg, and bilateral ptosis repeatedly following BTA injection into neck muscles. The mechanisms for these idiosyncratic adverse responses are not known.

New options for treatment of Parkinson's disease

New medications recently developed for treating Parkinson's disease include two inhibitors of catechol-O-methyltransferase (COMT), entacapone and tolcapone, which, by decreasing the elimination of levodopa, extend the duration of its effects. Increased 'on' time and less 'wearing-off' symptomatology can be expected with the use of these COMT inhibitors. Two non-ergot dopaminergic agonists (pramipexole and ropinirole) and a long-acting ergoline (cabergoline) are also being introduced. These dopaminergic agonists, like the ergot derivatives currently available (bromocriptine, lisuride, and pergolide), are useful as adjuncts to levodopa, and are also efficacious as monotherapies.

Immunocytochemical detection of anti-hippocampal antibodies in Alzheimer's disease and normal cerebrospinal fluid

Immunocytochemical staining was performed to investigate the presence of anti-hippocampal antibodies in cerebrospinal fluid (CSF) from patients with probable Alzheimer's disease (AD) (n = 19), aged normal controls (n = 9), and young normal controls (n = 10). Marked staining of neurons in the granule cell layer of the dentate gyrus and in pyramidal neurons in CA1-3 of the rat hippocampus was observed in 5 AD CSF samples (26%), 1 aged control sample (11%), and 1 young control sample (10%). These differences were not statistically significant. One of the immunoreactive AD CSF specimens also contained high concentrations of C5b-9, the membrane attack complex. The infrequent occurrence of anti-hippocampal antibodies in AD CSF, and the detection of similar immunoreactivity in control CSF specimens, suggest that these antibodies are unlikely to play a role in the neurodegenerative process in most individuals with AD. However, elevated C5b-9 concentration in an AD CSF specimen with marked immunoreactivity to hippocampal neurons suggests the possibility that anti-neuronal antibodies may contribute to complement activation in some AD patients.

Increased regional brain concentrations of ceruloplasmin in neurodegenerative disorders

Ceruloplasmin (CP), the major plasma anti-oxidant and copper transport protein, is synthesized in several tissues, including the brain. We compared regional brain concentrations of CP and copper between subjects with Alzheimer's disease (AD, n = 12), Parkinson's disease (PD, n = 14), Huntington's disease (HD, n = 11), progressive supranuclear palsy (PSP, n = 11), young adult normal controls (YC, n = 6) and elderly normal controls (EC, n = 7). Mean CP concentrations were significantly increased vs. EC (P < 0.05) in AD hippocampus, entorhinal cortex, frontal cortex, and putamen. PD hippocampus, frontal, temporal, and parietal cortices, and HD hippocampus, parietal cortex, and substantia nigra. Immunocytochemical staining for CP in AD hippocampus revealed marked staining within neurons, astrocytes, and neuritic plaques. Increased CP concentrations in brain in these disorders may indicate a localized acute phase-type response and/or a compensatory increase to oxidative stress.

Transferrin and iron in normal, Alzheimer's disease, and Parkinson's disease brain regions

Oxidant-mediated damage is suspected to be involved in the pathogenesis of several neurodegenerative disorders. Iron promotes conversion of hydrogen peroxide to hydroxyl radical and, thus, may contribute to oxidant stress. We measured iron and its transport protein transferrin in caudate, putamen, globus pallidus, substantia nigra, and frontal cortex of subjects with Alzheimer's disease (n = 14) and Parkinson's disease (n = 14), and in younger adult (n = 8) and elderly (n = 8) normal controls. Although there were no differences between control groups with regard to concentrations of iron and transferrin, iron was significantly increased (p < 0.05) in Alzheimer's disease globus pallidus and frontal cortex and Parkinson's disease globus pallidus, and transferrin was significantly increased in Alzheimer's disease frontal cortex, compared with elderly controls. The transferrin/iron ratio, a measure of iron mobilization capacity, was decreased in globus pallidus and caudate in both disorders. Regional transferrin and iron concentrations were generally more highly correlated (Pearson's correlation coefficient) in elderly controls than in Alzheimer's and Parkinson's disease. The altered relationship between iron and transferrin provides further evidence that a disturbance in iron metabolism may be involved in both disorders.

Markers of dopamine depletion and compensatory response in striatum and cerebrospinal fluid

Though depletion of CSF homovanillic acid (HVA) concentration has often been regarded as a direct indicator of dopamine (DA) deficiency in Parkinson's Disease (PD), CSF HVA is normal in mildly affected patients. To explore why, we measured DA and its metabolites in striatum and CSF in rabbits receiving reserpine for 5 days. Reserpine, which depletes striatal DA by disrupting vesicular storage of the neurotransmitter, results in a compensatory increase of DA turnover. In response to a 96% depletion of striatal DA, its catabolic intermediates 3,4-dihydroxyphenylacetic acid (DOPAC) and 3-methoxytyramine (3-MT) decreased 64% and 92% in striatum, although the endproduct, HVA, was unchanged. In contrast, CSF concentrations of HVA and DOPAC increased significantly, though 3-MT and levodopa (LD) were unaltered. A 5-fold rise in striatal LD concentration after reserpine-induced DA depletion provided evidence for enhanced DA synthesis. As in PD, the compensatory increase of DA synthesis after reserpine administration confounds the ability of CSF HVA to reflect DA depletion.

Perceived exertion and muscle efficiency in Parkinson's disease: L-DOPA effects

Weakness, easy fatiguing, and lack of endurance are commonly perceived by patients with Parkinson's disease (PD). Although the slowed motor repertoire in PD may underlie these experiences, other abnormalities in skeletal muscle utilization also may be involved. We investigated whether an index of metabolic efficiency during a continuous exercise task, the latency until anaerobic threshold (AT), is altered by L-DOPA (LD). While pedalling a bicycle ergometer against a uniform workload, subjects were monitored for expired O2 and CO2. As compared to an unmedicated state, LD treatment delayed AT by a mean (+/-SE) of 5.67 +/- 0.89 to 6.62 +/- 1.23 min (p < 0.05), paired t test). Subjects did not differ in their perceived exertion upon reaching AT. With relief of parkinsonism by LD, the efficiency of energy utilization is also increased in exercised skeletal muscle.

Effects of enhanced striatal dopamine turnover in vivo on glutathione oxidation

In Parkinson's disease (PD), a compensatory increase in dopamine (DA) turnover occurs in the remaining nigrostriatal dopaminergic neurons, resulting in greater exposure of each neuron to hydrogen peroxide (H2O2) derived from oxidative deamination of DA. The formation of oxyradicals from H2O2 is regarded as a mechanism that could contribute to the progression of PD, and incubation of rat striatal synaptosomes with levodopa (LD) results in an increase in oxidized glutathione (GSSG), indicative of oxidant stress. The present study was undertaken to determine whether striatal GSSG levels increase in response to administration of LD in vivo. Acute and repeated (3-week) treatment of normal rats with LD at doses of up to 100 mg/kg did not increase striatal GSSG despite marked increase in DA turnover. These results suggest that intact striatum may possess increased defense capacity against oxidant stress generated by increased DA turnover as compared with isolated synaptosomes.

Ceruloplasmin is increased in cerebrospinal fluid in Alzheimer's disease but not Parkinson's disease

Although the pathophysiology of Alzheimer's disease (AD) and Parkinson's disease (PD) is unknown, altered brain antioxidative mechanisms have been found in both disorders. Ceruloplasmin (CP) and transferrin (TF) interact to limit concentrations of free ferrous iron (Fe2+), and thus play an important role in antioxidant defense in serum; both proteins are also produced in brain, where their significance as antioxidants is unknown. We quantified concentrations of CP and TF by immunoassay in AD (n = 17) and PD (n = 12) cerebrospinal fluid (CSF) to determine whether these proteins could serve as disease markers. CP was increased versus aged normal subjects (n = 11) in AD (p < 0.05) but not PD CSF, whereas TF concentrations did not differ between groups. CP levels have been reported to be elevated in some brain regions in AD, and increased CP in AD CSF may reflect this finding. Systemic inflammation and oxidative stress are major factors stimulating hepatic CP synthesis, and it remains to be determined whether increased CP concentrations in AD CSF and brain follow from similar mechanisms.

Levodopa therapeutics: new treatment strategies

Even though levodopa can provide effective therapy for symptomatic relief of parkinsonism, many patients deteriorate over time. This change may be related to a loss of storage capability for dopamine in the brain affected by parkinsonian changes. Some of the variability in drug action is determined by its peripheral pharmacokinetics. Methods that can enhance dose-by-dose effectiveness, including controlled-release preparations and enteral infusions, have practical applications for managing "wearing-off" or peak-effect problems.

Symptomatic anti-parkinsonian effects of monoamine oxidase-B inhibition: comparison of selegiline and lazabemide

Selegiline (deprenyl) and lazabemide (Ro 19-6327) are inhibitors of monoamine oxidase-B but differ in several other pharmacological properties. We compared 4-week monotherapy trials of each to assess their actions against signs and disabilities of Parkinson's disease (PD). In a group of 20 mildly affected Parkinson patients treated with each drug, there were no statistically significant changes from the pretreatment baseline. There were no differences between the drugs. This work confirms that the symptomatic effects of selegiline against Parkinsonism are small and are likely due to its inhibition of monoamine oxidase-B.

Persistent movement disorders induced by buspirone

Buspirone, an azospirone compound, is a nonsedative anxiolytic that has achieved wide usage since its introduction in 1987. Although relatively free of side-effects, there have been several instances of dyskinesia and dystonia associated with the use of buspirone. We report two patients with persistent movement disorders that developed after prolonged treatment with the drug. One patient developed a lasting problem of cervical-cranial dystonia and tremors after treatment with buspirone at a dosage of 40 mg/day for several weeks. Another, receiving 30 mg/day for 6 weeks, experienced an exacerbation of preexisting spasmodic torticollis and tardive dyskinesia as well as the onset of involuntary phonations. As shown by these and other examples, buspirone poses the risk for inducing or exacerbating several types of movement disorders.

Neuroprotection by anti-oxidant strategies in Parkinson's disease

The advance of Parkinson's disease has been suspected to be an outcome of oxidative stresses related to the metabolism of dopamine. Several recent studies have tested whether deprenyl (selegiline) or alpha-tocopherol (vitamin E) might attenuate the progression of Parkinson's disease. Although preliminary results of an 800-patient controlled clinical trial (DATATOP) suggested in 1989 that neuroprotection might be achieved with deprenyl, more recent analysis has questioned this conclusion. The apparent protective effect of deprenyl is lost after 1 year of treatment, and the drug's symptomatic antiparkinsonian effects confound an understanding of actions on the underlying disease. In the DATATOP trial, no neuroprotection was achieved with alpha-tocopherol. Methods developed in the deprenyl trials and newly discovered CSF markers of Parkinson's disease may be useful tools for future investigations of neuroprotective strategies against Parkinson's disease.

Markers of dopamine metabolism in Parkinson's disease. The Parkinson Study Group

We used two analytic methods (a multichannel coulometric electrode array with high-performance liquid chromatography, and gas chromatography-mass spectrophotometry) to measure CSF dopamine (DA) and its metabolites in mildly affected, unmedicated subjects with Parkinson's disease (PD). The mean (+/- SD) concentration of homovanillic acid (HVA), the most abundant product of DA turnover, was 164.57 +/- 95.05 nM. As sequential aliquots of CSF were collected from the first to 23rd ml, CSF HVA concentration almost doubled. After HVA, 3-O-methyldopa (3-O-MD) was the next most abundant compound. The summed concentrations of 3-O-MD, 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine, DA, DA-3-sulfate, homovanillol, and levodopa (LD) amounted to 12.6% of HVA. Concentrations of the DA metabolites did not correlate to a variety of indices of PD severity. The presence of LD and 3-O-MD may be indicators of DA synthesis and possibly could reflect compensatory processes among surviving dopaminergic neurons of the PD brain.

Non-specific binding of normal human IgG, including F(ab')2 and Fc fragments, to embryonic rat brain neurons and human cortex synaptosomes

Binding of normal human IgG to embryonic rat brain neurons was quantitated by flow cytometry. IgG binding was linear between 0.05 and 1.5 mg/ml; slight binding was detectable even at normal cerebrospinal fluid concentrations. Similar binding curves were obtained for purified Fc and F(ab')2 fragments from normal human IgG. Normal human IgG also bound to synaptosomes (resealed nerve terminals) from human cerebral cortex. However, competition assays utilizing 125I-IgG showed no evidence for specific binding. This study indicates that the specificity of putative anti-neuronal antibodies should be confirmed by competition assays as for other receptor-ligand binding.

Treatment strategies for extension of levodopa effect

The initial benefits of levodopa decline for as many as half of all patients with Parkinson's disease treated for 2 years or more. Although levodopa is the most effective means for symptom relief, many parkinsonian patients lose the consistency of optimal symptom control. The variability experienced by such patients may arise from several alternative mechanisms at the level of the central nervous system (e.g., a narrowed therapeutic window for receptor-mediated effects or the loss of storage capability for dopamine in the parkinsonian brain). Whatever the cause, several practical methods have been developed. Dopaminergic agonists have played a major role in improving such problem. There are also several strategies for enhancing levodopa's dose by dose effectiveness, including sustained-release levodopa preparations and enteral infusions of levodopa. Another approach is the use of selegiline (deprenyl), MAO-B inhibitor slowing the breakdown of dopamine and thereby extending the duration of levodopa effect. Although selegiline can lessen the abruptness of levodopa wearing off, it can also exacerbate undesired peak effects of the drug. Clinical trials are planned with levodopa pro-drugs and inhibitors of catechol-O-methyltransferase to learn if these approaches can improve problems of long-term levodopa therapy.

Increased CSF HVA response to arecoline challenge in Alzheimer's disease

The effects of the muscarinic agonist, arecoline, on the concentration of homovanillic acid (HVA) in the cerebrospinal fluid of patients with Alzheimer's disease (AD) and controls were examined. Patients and controls received intravenous infusions of arecoline and a lumbar puncture was performed four hours after the infusion began. Arecoline induced a significant increase in the concentration of HVA in cerebrospinal fluid of Alzheimer's disease patients (p < .01) but not in controls. The differential HVA response to a muscarinic agonist in Alzheimer's disease is suggestive of an alteration in muscarinic receptor response. This finding may have potential implications for the pathophysiology and treatment of Alzheimer's disease.

Glutamate and other CSF amino acids in Alzheimer's disease

The authors compared CSF amino acid levels of 10 patients with mild to moderate dementia and probable Alzheimer's disease who had never received antidepressant or neuroleptic medication with those of 10 normal subjects of similar age. The Alzheimer's patients had significantly higher levels of CSF glutamate. This finding was not related to age, sex, or severity of dementia. Elevated CSF glutamate may reflect greater glutamatergic activity early in the course of Alzheimer's disease. The authors speculate that the excitotoxic effects of glutamate may contribute to progressive neuronal loss in Alzheimer's disease.

Clinical studies with and pharmacokinetic considerations of sustained-release levodopa

Although levodopa is the most effective antiparkinson agent yet available, strategies for improving the constancy of levodopa delivery to the brain are sometimes needed to optimize its actions. Its most common formulation is Sinemet, a combination of levodopa and carbidopa. Conventional Sinemet is absorbed and metabolized over 3 to 4 hours; however, Sinemet CR, a sustained-release preparation of 200 mg of levodopa and 50 mg of carbidopa, offers a duration of effect almost double that of Sinemet 25/100. In an 8-week trial with 25 parkinsonian patients, those treated with Sinemet CR required fewer daily doses than with the conventional Sinemet formulation and experienced improved "on" times (although improvements were not evident in all motor-fluctuation situations). The best therapeutic strategy may be a combination of the two Sinemet preparations, conventional Sinemet 25/100 as a booster dose and Sinemet CR for more sustained effect.

Deprenyl's effect at slowing progression of parkinsonian disability: the DATATOP study. The Parkinson Study Group

Studying a cohort of 800 mildly-affected parkinsonians, the North American DATATOP* project has concluded that progression in disability can be attenuated by the use of deprenyl, 10 mg/day. Interim results of this controlled clinical trial were reported after participants received treatment for an average of 12 months. The study found that deprenyl treatment almost halved the risk of reaching a stage of Parkinsonism at which the start of levodopa treatment becomes imperative for lessening disability. In addition to this study end-point, other ratings supported an improved clinical outcome from the chronic deprenyl (DP) regimen. The 34 investigators conducted clinical evaluations both while subjects received medication and after a 4-week wash-out. Though some subjects experienced mild symptomatic improvements of Parkinsonism from DP, these effects were insufficient to account for the DP-treated group's delay at reaching the study end-point. In addition to DP, this placebo-controlled double-blind study also assessed the possibility of protective effects from another antioxidative strategy, a 2,000 I.U./day regimen of alpha-tocopherol. To date, results of the latter trial have not been reported. Monoamine oxidase type-B (MAO-B) metabolism of dopamine generates hydrogen peroxide and, thereby, an oxidative stress on the nigrostriatal dopaminergic neuron. The inhibition of MAO-B by DP may have been the means by which progression of Parkinsonism was attenuated, although other mechanisms are also tenable. DATATOP has pointed to the potential for arresting the progression of Parkinson's disease, and has provided an unparalleled opportunity to study the clinical course and neurochemical indices of untreated Parkinsonism.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of MK-458 (HPMC) in Parkinson's disease previously untreated with dopaminergic drugs. A double-blind, placebo-controlled multicenter study

Ninety-four patients with early Parkinson's disease were investigated in a double-blind, placebo-controlled evaluation of MK-458 [hydroxypropyl methylcellulose/lactose matrix (HPMC)], a sustained release formulation of a novel naphthoxazine compound with selective D-2 dopamine receptor agonism. Patients were previously untreated with dopaminergic drugs. Efficacy was assessed by clinical rating scales and by patient self-evaluation. MK-458 (HPMC) caused a significant decrease in most parkinsonian symptoms. Though disability rating scores were lowered by the drug, the scores did not differ significantly from placebo. However, statistically significant improvement occurred with MK-458 (HPMC) on both the physician and the patient global assessments. Adverse reactions such as nausea and vomiting, sedation, confusion, and hallucinations occurred more with MK-458 (HPMC) than with placebo. MK-458 (HPMC) possesses antiparkinsonian efficacy in early Parkinson's disease; however, side-effects are frequently associated with its use. Selective D-2 receptor agonists, such as MK-458 (HPMC), may not be the ideal treatment as monotherapy for Parkinson's disease.

Effect of aging on tyrosine hydroxylase protein content and the relative number of dopamine nerve terminals in human caudate

This study examined the effect of aging on the relative number of dopamine (DA) nerve terminals in human caudate nucleus, their content of tyrosine hydroxylase (TH) protein, and the relative abundance of TH monomers with different molecular weights. Preliminary studies on brain tissue cryopreservation, performed with rat striatum, indicated that intact synaptosomes can be prepared from fresh tissue slowly frozen in 0.32 M sucrose with 5% dimethyl sulfoxide and then thawed rapidly prior to synaptosome preparation. Synaptosomes were prepared in this manner from postmortem caudate nucleus tissue obtained from normal humans 1 month to 63 years of age. To determine the relative number of DA nerve terminals for each individual, dopaminergic synaptosomes were selectively labeled with a monoclonal antibody to TH and quantified by fluorescence-activated cell sorting. To determine the relative amount of TH protein for each individual, the concentration of TH protein in the same synaptosomal preparations was determined using immunoblots. Our results suggest that caudate TH levels plateau soon after birth and tend to remain relatively stable during aging, since no changes in either the relative number of TH-containing nerve terminals or the concentration of TH protein were found in subjects 15-63 years of age. In light of previous studies showing an age-related loss of DA cell bodies, these findings suggest that remaining DA neurons compensate to maintain caudate levels of TH protein and TH-containing nerve terminals. Immunoblot studies identified three forms of TH monomer (60.6, 61.7, and 65.1 kDa), indicating that mRNAs coding for high molecular mass forms of TH may be actively translated in human brain. No age-related differences in the relative abundance of these forms were found.

Influence of age and gender on the levels of histamine metabolites and pros-methylimidazoleacetic acid in human cerebrospinal fluid

The metabolites of histamine, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), were measured in cerebrospinal fluid (CSF) from 47 subjects with neurological disorders and healthy controls. In lumbar CSF, concentrations of these metabolites were significantly correlated. Levels of t-MH, t-MIAA and their sum (which represents virtually all histamine metabolized in brain) were significantly higher in CSF from older subjects and were positively correlated with age. Females had higher levels of histamine metabolites than males. Males had higher levels of pros-methylimidazoleacetic acid (p-MIAA), an isomer of t-MIAA that is not a metabolite of histamine. Levels of p-MIAA increased with age among men. Analysis of covariance indicated that the subjects' health status had little or no effect on age- or sex-related differences in levels of analytes in CSF; sex-related differences were independent of changes attributed to age. These results are in contrast to those of age-related effects on levels of other aminergic transmitter metabolites in CSF and suggest that metabolic activity of histamine in brain may increase with age.

Influence of age and gender on the levels of histamine metabolites and pros-methylimidazoleacetic acid in human cerebrospinal fluid

The metabolites of histamine, tele-methylhistamine (t-MH) and tele-methylimidazoleacetic acid (t-MIAA), were measured in cerebrospinal fluid (CSF) from 47 subjects with neurological disorders and healthy controls. In lumbar CSF, concentrations of these metabolites were significantly correlated. Levels of t-MH, t-MIAA and their sum (which represents virtually all histamine metabolized in brain) were significantly higher in CSF from older subjects and were positively correlated with age. Females had higher levels of histamine metabolites than males. Males had higher levels of pros-methylimidazoleacetic acid (p-MIAA), an isomer of t-MIAA that is not a metabolite of histamine. Levels of p-MIAA increased with age among men. These results are in contrast to those of age-related effects on levels of other aminergic transmitter metabolites in CSF and suggest that metabolic activity of histamine in brain may increase with age.