David A. Durden

Aliphatic propargylamines: New antiapoptotic drugs

Two series of drugs, the aliphatic‐N‐methyl propargylamines and the aliphatic propargylamines, have been synthesised and shown to be specific, irreversible, and potent monoamine oxidase B inhibitors and neural rescue agents. In the latter case, an absolute stereochemical requirement for the R isomer exists. Both series of compounds have been shown, in numerous in vitro and in vivo experimental paradigms, to be effective neuronal rescue agents. Candidates from both series exhibit excellent bioavailability and pharmacokinetics and offer opportunities for treating neurodegenerative disorders and stroke and cognitive decline in companion animals. Drug Dev. Res. 42:150–156, 1997.

Stereospecific deuterium substitution at the α-carbon position of dopamine and its effect on oxidative deamination catalyzed by MAO-A and MAO-B from different tissues

Stereospecific replacement of deuterium in the alpha-carbon side chain position of dopamine (DA) was achieved by decarboxylation of L-3,4-dihydroxyphenylalanine (L-dopa) using hog kidney aromatic aminoacid decarboxylase. The S[alpha-2H1]DA enantiomer was obtained by decarboxylation of L-[alpha-2H1]dopa in H2O, while the R[alpha-2H1]DA enantiomer was obtained by decarboxylation of unsubstituted L-dopa in 2H2O. An inverse solvent isotope effect of L-dopa decarboxylation was observed in 2H2O. The deaminated aldehyde products of the four DA analogues, i.e. undeuterated DA, [alpha, alpha-2H2] DA, R[alpha-2H1]DA and S[alpha-2H1]DA, have been analyzed by the gas chromatography-mass spectrometry (GC-MS) method. It is evident that monoamine oxidase (MAO) catalyzes the stereochemical removal of only R-deuterium and that S-deuterium was maintained at the alpha-carbon atom of 3,4-dihydroxyphenylacetaldehyde. The steady-state kinetics of the oxidative deamination of undeuterated, [alpha, alpha-2H2], R[alpha-2H1], and S[alpha-2H1] dopamine were assessed by determination of the aldehyde products directly by high performance liquid chromatography (HPLC) using electrochemical detection (ECD). MAO-A from rat liver mitochondria (deprenyl-treated) and from human placenta, as well as MAO-B from rat liver (clorgyline-treated) and from human platelet were used in this study. The apparent isotope effects, i.e. (V/K)H/(V/K)D ratios of [alpha, alpha-2H2]DA and R[alpha-2H1]DA, were quite similar (2.34 and 3.13) with respect to both MAO-A and MAO-B. S[alpha-2H1]DA exhibited a slight secondary isotope effect. Formula: see text.

Hydroxylation of β-phenylethylamine in the rat

Abstract ortho , meta and para Tyramine, as their dansyl derivatives, have been identified and quantitated by mass spectrometry in rat urine. After intraperitoneal injection of phenylethylamine labelled either with deuterium or tritium in the presence of pargyline, the amount of urinary tyramines excreted was 0.8% ( para , 0.74%; meta , 0.12%; ortho , 0.008%) of the injected dose. The advantages of involving stable isotopes and mass spectrometry in metabolic studies of pharmacologically active compounds is discussed.

The effect of L-deprenyl on behavior, cognitive function, and biogenic amines in the dog

Behavioral and pharmacological effects of oral administration ofl-deprenyl in the dog are described. Spontaneous behavior is unaffected at doses below 3 mg/kg while at higher doses there was stereotypical responding. There was evidence of improved cognitive function in animals chronically treated with a 1 mg/kg dose but the effectiveness varied considerably between subjects. Chronic administration produced a dose dependent inhibition in brain, kidney and liver monoamine oxidase B, and had no effect on monoamine oxidase A. There were also dose dependent increases in brain phenylethylamine and in plasma levels of amphetamine. Dog platelets did not have significant levels of MAO-B. Brain dopamine and serotonin metabolism were unaffected byl-deprenyl at doses up to 1 mg/kg. It appears that for the dog, deamination of catecholamines is controlled by MAO-A. Nevertheless, it is suggested thatl-deprenyl serves as a dopaminergic agonist, and there is also evidence that it affects adrenergic transmission. These catecholaminergic actions may account for the effects ofl-deprenyl on behavior and cognitive function.

Simultaneous analysis of twelve biogenic amine metabolites in plasma, cerebrospinal fluid and urine by capillary column gas chromatography-high-resolution mass spectrometry with selected-ion monitoring.

A procedure is described for the simultaneous determination of twelve acidic and alcoholic metabolites of trace and catecholic biogenic amines in plasma, cerebrospinal fluid and urine by capillary column gas chromatography--high-resolution mass spectrometry. Protein precipitation with sulphosalicylic acid, derivatization with two different reagent systems, final sample clean-up with a buffer wash and a program for automatically changing the reference mass of the mass spectrometer to suit each group of compounds as they are eluted from the column, are the main novel features of the procedure. A brief description of the synthesis of the deuterium-labelled internal standards is provided. The procedure is applied to biological samples and a comparison to reported values is given.

The distribution and turnover of tryptamine in the brain and spinal cord

Tryptamine levels have been determined in mouse brain regions and spinal cord and in rat spinal cord. They were; caudate nucleus 2.5 ng·g−1, hypothalamus <0.5 ng·g−1, hippocampus <0.7 ng·g−1, olfactory bulb <0.7 ng·g−1, olfactory tubercles <0.6 ng·g−1, brain stem <0.4 ng·g−1, cerebellum <1.0 ng·g−1, and the “rest” 0.9 ng·g−1. The mouse whole brain was found to have 0.5 ng·g−1, the mouse spinal cord 0.3 ng·g−1, and the rat spinal cord 0.3 ng·g−1. These concentrations increased rapidly to 22.8 ng·g−1, 14.2 ng·g−1, and 6.6 ng·g−1 respectively at 1 hr after 200 mg·kg−1 pargyline. The turnover rates and half lives of tryptamine in the mouse brain and spinal cord and rat spinal cord were estimated to be 0.14 nmol·g−1·h−1 and 0.9 min; 0.054 nmol·g−1·h−1 and 1.5 min and 0.04 nmol·g−1·h−1 and 1.6 min respectively. The aromaticl-aminoacid decarboxylase inhibitors NSD 1034 and NSD 1055 reduced synthesis of tryptamine in controls and pargyline pretreated animals. Tryptophan increased the concentrations of mouse striatal tryptamine and 5-hydroxytryptamine and brain stem 5-hydroxyindole acetic acid.p-Chlorophenylalanine reduced formation of 5-hydroxytryptamine and 5-hydroxyindoleacetic acid but did not change that of tryptamine.

Neurochemical and Neuroprotective Effects of Some Aliphatic Propargylamines: New Selective Nonamphetamine-Like Monoamine Oxidase B Inhibitors

Abstract: Aliphatic N‐propargylamines have recently been discovered to be highly potent, selective, and irreversible monoamine oxidase B (MAO‐B) inhibitors. N‐Methyl‐N‐(2‐pentyl)propargylamine (M‐2‐PP) and N‐methyl‐N‐(2‐hexyl) propargylamine (2‐HxMP), for example, are approximately fivefold more potent than I‐deprenyl at inhibiting mouse brain MAO‐B activity following oral administration. These inhibitors are nonaromatic compounds and are chemically quite different from other known MAO‐B inhibitors. Some of their neurochemical and neuroprotective properties have been evaluated and compared with those of I‐deprenyl. We have confirmed that these new inhibitors selectively inhibit MAO‐B activity both in vitro and in vivo. 2‐Phenylethylamine levels were substantially increased following administration of M‐2‐PP, but the levels of dopamine, 3,4‐dihydroxyphenylacetic acid, homovanillic acid, 5‐hydroxytryptamine, and 5‐hydroxyindoleacetic acid were not affected except at high, nonselective doses. Chronic oral administration of I‐deprenyl and M‐2‐PP causes selective inhibition of MAO‐B activity and increases dopamine levels in mouse caudate. M‐2‐PP, like I‐deprenyl, has been shown to be potent in protecting against MPTP‐induced damage in the mouse. N‐(2‐Chloroethyl)‐N‐ethyl‐2‐bromobenzylamine (DSP‐4), a noradrenaline neurotoxin, is not an MAO substrate. Its noradrenaline‐depleting effects were substantially mitigated by I‐deprenyl as well as by M‐2‐PP and 2‐HxMP in the mouse hippocampus. Administration of 2‐phenylethylamine, however, failed to reverse the effect of DSP‐4. The neuroprotective effect of M‐2‐PP and 2‐HxMP is apparently unrelated to the uptake of DSP‐4.

Plasma phenylethylamine in schizophrenic patients

Plasma samples were collected from 41 patients who met DSM-III criteria for schizophrenia and from 34 healthy controls. Phenylethylamine (PE) levels were determined using a gas chromatography-mass spectrometry negative chemical ionization method. PE was significantly higher in the schizophrenic patients compared with controls. There were no differences in PE between paranoid and nonparanoid patients. Plasma PE did not appear to be influenced by the severity of schizophrenic symptoms (rated by BPRS, SANS, and SAPS) or by the amount of dietary phenylalanine ingested within 24 hr of testing. Plasma PE did not correlate with current or past exposure to neuroleptic medication. It was not possible, however, to test individual patients during two periods when they were taking and not taking medication. Thus it is possible that neuroleptic exposure may have confounded the results. This study provides further evidence that PE excess may play a role in the etiology of schizophrenia but does not support previous studies which suggest that such an abnormality is limited to the paranoid subgroup.

Plasma concentrations of p- and m-hydroxyphenylacetic acid and phenylacetic acid in humans : Gas chromatographic—high-resolution mass spectrometric analysis

Conjugated and unconjugated phenylacetic acid and m- and p-hydroxyphenylacetic acid have been determined in the plasma of normal, healthy subjects after fasting, consumption of a meal and ingestion of deuterium labelled amine precursors, by high-resolution gas chromatography--high resolution mass spectrometry with selected ion monitoring of their trifluoroethyl-pentafluoropropionyl derivatives. We observed tht all three conjugated acids are higher in fasting than in non-fasting subjects, and unconjugated phenylacetic acid was lower. Ingestion of deuterium-labelled amine precursors resulted in the appearance in the blood of the correspondingly labelled acids, a peak in the concentrations being reached about 1 h after consumption. Conjugated and unconjugated acids as expected increased following the consumption of a meal. Unconjugated phenylacetic acid was significantly higher in females than in males. Most values tended to increase with age, with male unconjugated and conjugated m-hydroxyphenylacetic acid and female conjugated phenylacetic and m-hydroxyphenylacetic acids increasing significantly.

The analysis of certain amines in tissues and body fluids as their dansyl derivatives.

Abstract A general procedure for the isolation and chromatographic separation of some biogenic amines, as their Dansyl 1 derivatives, and their quantitative evaluation by a mass spectrometric procedure is described. In the case of β-phenylethylamine, which has been used as a typical example, the endogenous tissue concentrations (ng/g) in the rate were: spleen, 4.7 ± 2.7; lung, 4.0 ± 1.4; liver, 2.0 ± 0.7; kidney, 20.5 ± 2.2; heart, 5.7 ± 3.1; and brain 1.8 ± 0.4. After treatment with various monoamine oxidase inhibitors these values increased between 7 and 198 times.