Monoamine Oxidase

Monoamine oxidase (MAO) occupies a structurally important position in the depth-psychology corpus wherever neurobiological accounts of affect, aggression, mood, and pharmacological intervention intersect with psychological theory. The enzyme appears across several registers: as a catabolic regulator whose inhibition constitutes the pharmacological rationale for the earliest antidepressants (MAOIs), as a genetic locus whose variant activity levels correlate with heritable aggression and violence-proneness, and as a hormonally modulated system whose activity fluctuates with the estrous and menstrual cycles, thereby linking female endocrinology to dopaminergic sensitivity. Kandel illuminates its clinical-historical significance as the enzyme whose inhibition launched biological psychiatry's first effective antidepressant. Panksepp situates MAO-A plasma activity within the neurochemistry of sociopathy and familial aggression patterns. Justice and colleagues demonstrate that estrogen decreases MAO activity, linking catecholamine availability to hormonal state. Faraone's pharmacological review documents amphetamine's capacity to inhibit both MAO-A and MAO-B. Schore's bibliographic apparatus cites foundational MAO scholarship at the subcellular level. Together, these treatments render MAO a fulcrum between genetic endowment, developmental environment, hormonal regulation, and the pharmacological modification of psychic states — a genuinely translational node in psychobiological theory.

In the library 10 passages

The first one—a monoamine oxidase inhibitor (MAOI)—was initially developed to fight a very different disorder, tuberculosis. MAOIs act by decreasing the breakdown of serotonin and norepinephrine, thereby making more of these neurotransmitters available

Kandel establishes the MAOI as the historically inaugural antidepressant, grounding its mechanism explicitly in MAO's role as the catabolic enzyme for serotonin and norepinephrine.

Kandel, Eric R., In search of memory the emergence of a new science of mind, 2006thesis

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certain families with very high levels of aggression have been found to be characterized by neurochemical traits such as high plasma monoamine oxidase-A (MAO-A) activity, the enzyme that breaks down several biogenic amines, including serotonin, within the brain.

Panksepp ties heritable aggression and sociopathy to elevated plasma MAO-A activity, positioning the enzyme as a biochemical correlate of constitutionally violent temperament.

Panksepp, Jaak, Affective Neuroscience The Foundations of Human and Animal, 1998thesis

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Estrogen also decreases monoamine oxidase activity, thereby regulating the degradation of dopamine.

Justice demonstrates that estrogen's enhancement of dopaminergic activity is partly mediated through suppression of MAO, directly coupling hormonal state to catecholamine availability.

Justice, Angela J.H., Acute effects of d-amphetamine during the follicular and luteal phases of the menstrual cycle in women, 1999thesis

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Robinson (1985) • AMP enantiomers (d and l) inhibited MAO type A and MAO type B activity in rat liver mitochondria

Faraone's pharmacological table documents that both amphetamine enantiomers inhibit MAO-A and MAO-B, establishing MAO inhibition as a secondary mechanism of amphetamine's neurochemical action.

Faraone, Stephen V., The pharmacology of amphetamine and methylphenidate: Relevance to the neurobiology of attention-deficit/hyperactivity disorder and other psychiatric comorbidities, 2018supporting

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Miller et al. (1980) • AMP inhibited MAO type A activity

Preclinical evidence cited by Faraone confirms amphetamine's inhibition of MAO type A as part of its broader mechanism of action on the monoaminergic system.

Faraone, Stephen V., The pharmacology of amphetamine and methylphenidate: Relevance to the neurobiology of attention-deficit/hyperactivity disorder and other psychiatric comorbidities, 2018supporting

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Shih, J. C., Chen, K. and Ridd, M. J. (1999). Monoamine oxidase: from genes to behavior Annual Review of Neuroscience, 22, 197–217. Caspi, A., McClay, J., Moffitt, T. et al. (2002). Role of genotype in the cycle of violence in maltreated children.

The Lanius volume cites the canonical 'MAO: from genes to behavior' monograph alongside Caspi's gene-by-environment study, linking MAO genetics to the intergenerational cycle of violence in maltreated children.

Lanius, edited by Ruth A, The impact of early life trauma on health and disease the, 2010supporting

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Convergent genetic modulation of the endocrine stress response involves polymorphic variations of 5-HTT, COMT and MAOA.

This bibliographic citation positions MAO-A polymorphism alongside serotonin transporter and COMT variants as converging genetic modulators of HPA-axis stress reactivity and trauma vulnerability.

Lanius, edited by Ruth A, The impact of early life trauma on health and disease the, 2010supporting

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Resnick, O., Krus, D. M, & Raskin, M. (1964). LSD-25 action in normal subjects treated with a monoamine oxidase inhibitor. Life Sci. 3:1207-1214.

Panksepp's footnote documents early psychopharmacological research showing that MAO inhibition potentiates the psychedelic effects of LSD, suggesting MAO's role in regulating serotonergic availability relevant to altered states.

Panksepp, Jaak, Affective Neuroscience The Foundations of Human and Animal, 1998supporting

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Costa, E., & Sandler, M. (1972). Monoamine oxidase: New vistas. New York: Raven Press.

Schore's bibliography references the foundational Costa and Sandler volume on MAO, situating the enzyme within the broader neurobiological framework of his developmental affect-regulation theory.

Schore, Allan N., Affect Regulation and the Origin of the Self: The Neurobiology of Emotional Development, 1994aside

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Mapping the amphetamine-evoked changes in [11C]raclopride binding in living rat using small animal PET: modulation by MAO-inhibition.

A cited study demonstrates that MAO inhibition modulates amphetamine-evoked dopamine release as measured by raclopride displacement PET, indicating MAO's regulatory role in stimulant pharmacodynamics.

Faraone, Stephen V., The pharmacology of amphetamine and methylphenidate: Relevance to the neurobiology of attention-deficit/hyperactivity disorder and other psychiatric comorbidities, 2018aside

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