Production of a Parkinson-like syndrome in the cat with N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP): behavior, histology, and biochemistry

N-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a potent dopaminergic neurotoxin, was administered to cats systemically for 5 to 7 days. This treatment produced a behavioral syndrome characterized by akinesia, ataxia, bradykinesia, and feeding difficulties, lasting for several weeks. During this period of severe behavioral impairment, caudate and nucleus accumbens dopamine and norepinephrine concentrations were quite depleted. Behavioral recovery ensued over the next several weeks as did some recovery of striatal catecholamines. MPTP destroyed the majority of substantia nigra pars compacta neurons while affecting a much lesser number of locus ceruleus and ventral tegmental neurons. These results demonstrated for the first time that MPTP can cause long-lasting deficits in nigrostriatal functioning in the cat and may provide a means for studying the apparently selective neurotoxic effects of MPTP as well as for understanding the pathophysiology of Parkinson's disease.

Positron emission tomography after MPTP: observations relating to the cause of Parkinson's disease

The dopa analogue 6-fluorodopa (6-FD) used with positron emission tomography (PET) allows in vivo visualization of dopamine and its metabolites in nigrostriatal nerve endings. We have now found abnormal 6-FD scans in four subjects exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). None had parkinsonism. The results suggest subclinical damage to the nigrostriatal pathway. This is the first direct evidence that dopaminergic impairment can exist without clinical deficits. Here we discuss this finding in the context of the hypothesis that Parkinson's disease may stem from clinically silent damage to the substantia nigra, followed by slow attrition of neurones in this region because of its particular vulnerability to cell loss as a normal consequence of ageing.

The clinical syndrome of striatal dopamine deficiency. Parkinsonism induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

Exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces a syndrome that resembles Parkinson's disease. To compare the biochemical abnormalities produced by this compound in human beings with those occurring in Parkinson's disease, we examined biogenic amine metabolites in cerebrospinal fluid and urine from six patients with MPTP-induced parkinsonism and eight patients with Parkinson's disease. In both forms of parkinsonism, the cerebrospinal fluid levels of homovanillic acid, the major metabolite of dopamine, were reduced, whereas the levels of the serotonin metabolite 5-hydroxyindoleacetic acid were normal. The cerebrospinal fluid levels of 3-methoxy-4-hydroxyphenylethylene glycol (MHPG), the major metabolite of norepinephrine in the brain, after adjustment for plasma MHPG, were elevated (greater than 6.0 ng per milliliter) in MPTP-induced parkinsonism, whereas MHPG levels were reduced (less than 6.0) in Parkinson's disease. Neurons containing norepinephrine in the brain are involved in the degenerative process of Parkinson's disease, whereas they are spared in MPTP-induced parkinsonism. The selective destruction by MPTP of nigrostriatal dopamine neurons that is responsible for the movement disorder also appears to result in an increase in central noradrenergic activity, which is not possible in Parkinson's disease. Thus, differences in central noradrenergic activity, reflected in cerebrospinal fluid levels of MHPG, distinguish these two forms of parkinsonism.

Aetiology of Parkinson's disease

It is suggested here that in most cases of Parkinson's disease the cause may be an environmental factor, possibly toxic, superimposed on a background of slow, sustained neuronal loss due to advancing age.

False-positive EMIT indication of opiates and methadone in a doxylamine intoxication

The EMIT-dau for methadone and the EMIT-ST for opiates (both EMITs from Syva-Merck) gave false-positive results when applied to urine samples of a patient suffering from a moderate doxylamine monointoxication. The error was not detected in routine TLC. Gas chromatography and mass spectrometry unequivocally indicated the presence in urine and plasma of doxylamine and its metabolites and the definite absence of methadone. Opiates could not be detected with the Abuscreen RIA (Roche), which is a more sensitive method than EMIT-ST.

[Therapy of acute poisoning with orthograde intestinal lavage]

Orthograde intestinal lavage was successfully used in the treatment of eight patients with acute poisoning. Three had mushroom (Amanita pantherina) poisoning, five acute drug intoxication (attempted suicide: diazepam, dihydropyridine, crotylbarbital, phenobarbital, amitriptyline and glibenclamide). Within 5-18 hours the clinical signs of poisoning regressed in four patient in stage IV (after Reed), so that the patients became responsive. Detoxication by orthograde intestinal lavage is achieved by mechanical removal of nonabsorbed compounds from the gastro-intestinal tract and via intestinal dialysis across the intestinal mucosa.

Mushroom poisoning caused by species of the genus Cortinarius Fries

Symptomatology, clinical characteristics and pathogenesis of mushroom poisoning caused by Cortinarius species are surveyed. The isolation of a bipyridine--orellanine--from Cortinarius orellanus is held to be responsible for the nephrotoxicity of this species as well as the closely related C. speciosissimus. The present knowledge on the toxicity of structurally related and well-known bipyridines such as paraquat and diquat is brought up and found comparable to orellanine toxicity. Pharmacokinetic experiments on the nephrotoxic bipyridines suggest that haemoperfusion is a rational therapy of intoxicated persons, even several days after mushroom ingestion.

The general toxicology unknown. II. A case report: doxylamine and pyrilamine intoxication

A general toxicology unknown case is presented to demonstrate our systematic approach. A 20-year-old male was found dead with multiple suicide notes. Overdose was suspected but substances were not known. Blood alcohol was negative. Urine was analyzed by enzyme-multiplied immunoassay technique and was negative for all drugs assayed. Urine was then extracted with ethyl acetate:hexane (1:1) at pH 10 and back-extracted into 1.0N sulfuric acid. The acidic layer was adjusted to pH 10, and re-extracted with ethyl acetate:hexane (1:1). The residue was analyzed by gas chromatography (GC) on a 3% OV-101 column. It was found to be negative for all commonly screened substances. However, several unknown peaks were observed. Electron impact mass spectra of these unknown peaks were obtained and searched for in our computer library of more than 25000 mass spectra. These unknown peaks were identified as doxylamine and pyrilamine by gas chromatography/mass spectrometry. The base peak and molecular ion for pyrilamine were at m/z 121 and 285, respectively. The base peak for doxylamine was at m/z 58. No molecular ion was observed for doxylamine. Both doxylamine and pyrilamine are antihistamines, but are promoted and used in the management of insomnia. Quantitation was performed on a GC using dexbrompheniramine as an internal standard. Blood concentrations for doxylamine and pyrilamine were 0.7 and 7.0 mg/L, respectively. Concentrations in other tissues were determined. Death was caused by combined doxylamine and pyrilamine intoxication; the manner of death was suicide.

Disopyramide fatality: case report and GC/FID analysis

This case involves massive ingestion of disopyramide by a 19-year-old male, found dead, not having had the benefit of medical intervention. Quantitation of the drug was accomplished by gas chromatography using a flame ionization detector (GC/FID). Identification of the compound was done by thin layer chromatography (TLC) and ultraviolet spectrophotometry (UVS). The blood concentration of disopyramide was 15 times the usual therapeutic level and was easily detected by FID.

[Acute voluntary or accidental disopyramide poisoning. A multicentric study of 106 cases (author's transl)]

Between 1972 and 1978, 106 case-records of disopyramide poisoning were collected from French anti-poison center. Acute intoxication was voluntary in 90% of the cases and occurred in young adults. Clinical symptoms appeared early and consisted mostly of cardiovascular disorders, which were present in 60 patients: cardiogenic shock (24 cases), circulatory arrest (17 cases), atrio-ventricular block (21 cases), intraventricular block (24 cases) and severe ventricular arrhythmia (12 cases). The toxic dose in otherwise healthy adults was 1,5 g and the mortality rate was high (12,2%). An analysis of therapeutic measures and outcome indicated that the best treatment consists of early gastric lavage, cardiorespiratory manoeuvres, electric heart stimulation, administration of sodium lactate in cases with intraventricular conduction disturbances and isoprenaline in cases with cardiogenic shock.

[Disopyramide poisoning]

Acute intoxications with the antiarrhythmic drug disopyramide (Norpace) are often life-threatening. After an almost asymptomatic interval of 1 to 4 hours, cardiogenic shock of sudden onset occurs. The usual methods of cardiac resuscitation such as adrenaline and antiarrhythmic drugs should not be used, and transvenous pacemakers often prove ineffective. To lower the high rate of mortality, early appropriate monitoring and facilities for rapid intervention are necessary. Isoprenaline is the most suitable positive inotropic and chronotropic drug. Hemoperfusion with Amberlite XAD 14 is effective but not always needed.

Safety data on zimelidine hydrochloride following an overdose

Zimelidine, a new antidepressant, has proved to be a potent and selective inhibitor of 5-HT uptake into central 5-HT neurons. Due to its structural differences from the tricyclic antidepressants, it has also been suggested that it may have a different pharmacological profile, and be devoid of anticholinergic and noradrenaline potentiating properties. During the treatment with zimelidine hydrochloride, as a part of an open trial, one of our patients, a 38-year-old chronically depressed woman, overdosed herself with more than 10 times the actual therapeutic dose of zimelidine with no undesirable side effects. Previous studies have indicated that zimelidine in comparison with imipramine and chlorimipramine has no, or at most, a slight effect on peripheral adrenergic neurons, and has less pronounced anticholinergic properties than imipramine. The findings of our overdose case provide some support for these findings.