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Monoamine oxidases of the brains and livers of macaque and cercopithecus monkeys
1Department of Neurology, University Hospitals of Cleveland, Ohio.
Abstract:
We assessed the two forms of monoamine oxidase (MAO), MAO-A and MAO-B, in discrete regions of the brain and in cerebral micro- and macrovessels, choroid plexus, and liver of three species of monkeys: African Green, rhesus, and cynomolgus. MAO was determined by specific [3H]pargyline binding which is stoichiometric and irreversible and by measuring the rate of oxidation of several substrates. Cerebral micro- and macrovessels had low MAO content. Regional brain MAO did not vary by more than one-fold in the brains of each of the three species of monkeys and was higher in the basal ganglia than in the cerebral cortex or cerebellum. MAO in the choroid plexus was low, while the liver had higher MAO activity than any of the brain samples. The vast majority of MAO in all the tissues that we examined was of the MAO-B type, and specific [3H]pargyline binding correlated well with the oxidation rate of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. These results show marked similarities in brain MAO distribution between monkey and man. Or the three monkey species, the African Green monkey had the lowest MAO activity in its cerebral microvessels, which constitute the blood-brain barrier, although the small number of observations in each group did not allow statistical analyses of the differences.
Insights
Monoamine oxidase (MAO) B is the predominant form in monkey tissues, including the brain and blood vessels. MAO distribution in monkey brains closely resembles that found in humans.
Area of Science:
- Neuroscience
- Biochemistry
- Pharmacology
Background:
- Monoamine oxidase (MAO) enzymes, specifically MAO-A and MAO-B, play crucial roles in neurotransmitter metabolism.
- Understanding MAO distribution is vital for developing targeted therapies for neurological disorders.
Purpose of the Study:
- To investigate the distribution and relative abundance of MAO-A and MAO-B in various monkey tissues.
- To compare MAO distribution in monkey brains and vasculature with human data.
Main Methods:
- Assessed MAO activity using specific [3H]pargyline binding and substrate oxidation rates.
- Examined MAO levels in discrete brain regions, cerebral micro- and macrovessels, choroid plexus, and liver of African Green, rhesus, and cynomolgus monkeys.
Main Results:
- MAO-B was the predominant MAO type across all examined monkey tissues.
- Cerebral micro- and macrovessels exhibited low MAO content.
- Regional brain MAO levels were relatively consistent, with higher concentrations in the basal ganglia compared to the cortex or cerebellum.
- Liver tissue showed higher MAO activity than brain samples.
- African Green monkeys displayed the lowest MAO activity in cerebral microvessels.
Conclusions:
- Monkey MAO distribution, particularly in the brain, shows significant similarities to that of humans.
- MAO-B is the primary MAO isoform in monkey brain and vasculature.
- Findings support the use of non-human primates as models for studying MAO-related human neurological conditions.