Comparative effects of dehydropirlindole and other compounds on rat brain monoamine oxidase type A

Effects of subchronic exposure to styrene on the extracellular and tissue levels of dopamine, serotonin and their metabolites in rat brain

At present, there is controversy over the neurotoxic potential of styrene. Several epidemiological and clinical studies have shown that styrene exposure causes alterations of central nervous system functions in humans. Neurotransmitters have been implicated in the pathogenesis of styrene neurotoxicity in rodents. Several studies carried out on postmortem brain tissue suggest that styrene may alter dopaminergic neurotransmission in rabbit or rat brain. Moreover, in vitro studies suggest that both styrene and styrene oxide inhibit the uptake of dopamine (DA) in purified synaptic vesicles prepared from rat brain striata. To date, biochemical studies on animals have explored global tissue levels of neurotransmitters with sub-acute exposures to styrene. However, extracellular levels of neurotransmitters are more closely related to behaviour than are global tissue levels. The present study determined changes in the extracellular concentrations of DA, serotonin (5-HT) and their acid metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA), in striatal dialysates from freely moving adult male rats after exposure to 750 and 1,000 ppm styrene, 6 h per day, 5 days per week for 4 weeks. We also determined the concentrations of DA, 5-HT and their acid metabolites in striatum, nucleus accumbens and prefrontal cortex obtained postmortem from similarly exposed rats. Exposure to 1,000 ppm of styrene caused a significant decrease in extracellular acid metabolite concentrations. Tissue levels of acid metabolites were also decreased to a lesser extent. The effects were observed 72 h after discontinuing exposure but had vanished 17 days later. There was no change in DA or 5-HT concentrations either in the dialysates or tissues. Exposure to 750 ppm styrene caused no changes in the concentrations of DA, 5-HT and their acid metabolites either in the dialysates or tissues. The possibility that the effect of styrene is mediated by monoamine oxidase (MAO) inhibition is discussed.

Monoamine oxidase inhibitor poisoning resulting from Internet misinformation on illicit substances

The Internet may represent a new mechanism by which adolescents initiate the use of illicit substances. The existence of multiple partisan websites providing misinformation regarding the safety of these substances may lead to an increase in unsafe behavior among this age group. Adverse outcomes related to Internet-based drug information are rarely identified. We report a case of an adolescent whose use of the Internet to obtain drug information led to severe poisoning from the combination of a monoamine oxidase inhibitor, harmaline, and a hallucinogenic tryptamine, 5-methoxydimethyltryptamine (5-MeO-DMT).

Pirlindole and dehydropirlindole protect rat cultured neuronal cells against oxidative stress-induced cell death through a mechanism unrelated to MAO-A inhibition

It has been shown that the MAO (monoamine oxidase)-B inhibitor deprenyl (DPR, selegiline) protects some cell types against oxidative stress. By decreasing H(2)O(2) production, MAO-A inhibitors could also reduce oxidative stress. This study reports the effect of the MAO-A inhibitors, pirlindole (PIR), dehydropirlindole (DHP), brofaromine (BRO) and moclobemide (MCL) on primary-cultured brain cells exposed to iron-mediated toxicity. A comparison with trolox (TRO), a hydrosoluble vitamin-E analogue that protects against such an induced stress, was performed. Rat hippocampal or cortical cultured cells were exposed either to 2 microM FeSO(4) alone or in the presence of PIR, DHP, BRO, DPR, MCL or TRO. Cell survival (lactate-dehydrogenase measurements, 16 h incubation), intracellular peroxide production (DCF-fluorescence, 1 h incubation), lipoperoxidation (TBARS-fluorescence, 6 h incubation) and mitochondrial function (MTT-test, 16 h incubation) were assessed. PIR, DHP and TRO significantly protected cultures (P<0.05) against Fe(2+)-induced toxicity in a concentration-dependent manner. The EC(50s) of these compounds were 6, 12 and 19 microM, respectively, in hippocampal cells. For cortical cell cultures incubated in the presence of iron and PIR or DHP, EC(50s) were 5 and 6 microM respectively. All Hill coefficients were close to unity. BRO, MCL and DPR were not protective in any type of culture. The IC(50s) for the inhibition of MAO-A were 2, 2 and 0.2 microM for PIR, DHP and BRO, respectively. PIR, DHP and TRO, but not DPR, induced a significant decrease in both intracellular peroxide production and lipoperoxidation. They also improved mitochondrial function. These experiments show that PIR and DHP can protect hippocampal and cortical neurons against oxidative stress at pharmacologically relevant concentrations. This protective effect seems unrelated to inhibition of MAO-A, but possibly involves free radical scavenging.