^ abcVytla D, Combs-Bachmann RE, Hussey AM, McCarron ST, McCarthy DS, Chambers JJ (May 2012). "Prodrug approaches to reduce hyperexcitation in the CNS". Adv Drug Deliv Rev. 64 (7): 666–685. doi:10.1016/j.addr.2011.11.007. PMID22138074.
^ abcJana S, Mandlekar S, Marathe P (2010). "Prodrug design to improve pharmacokinetic and drug delivery properties: challenges to the discovery scientists". Curr Med Chem. 17 (32): 3874–3908. doi:10.2174/092986710793205426. PMID20858214.
^Gupta HV, Lyons KE, Pahwa R (September 2019). "Old Drugs, New Delivery Systems in Parkinson's Disease". Drugs Aging. 36 (9): 807–821. doi:10.1007/s40266-019-00682-9. PMID31161581.
^Lees A, Tolosa E, Stocchi F, Ferreira JJ, Rascol O, Antonini A, Poewe W (January 2023). "Optimizing levodopa therapy, when and how? Perspectives on the importance of delivery and the potential for an early combination approach". Expert Rev Neurother. 23 (1): 15–24. doi:10.1080/14737175.2023.2176220. hdl:10451/56313. PMID36729395.
^Cacciatore I, Ciulla M, Marinelli L, Eusepi P, Di Stefano A (April 2018). "Advances in prodrug design for Parkinson's disease". Expert Opin Drug Discov. 13 (4): 295–305. doi:10.1080/17460441.2018.1429400. PMID29361853.
^Dhaneshwar SS, Sharma M, Patel V, Desai U, Bhojak J (2011). "Prodrug strategies for antihypertensives". Curr Top Med Chem. 11 (18): 2299–317. doi:10.2174/156802611797183285. PMID21671866.
^Lamoureux G, Artavia G (2010). "Use of the adamantane structure in medicinal chemistry". Current Medicinal Chemistry. 17 (26): 2967–2978. doi:10.2174/092986710792065027. PMID20858176. Dopamantine 4, the anti-Parkinson drug which has passed clinical trials, is also based on the ability of adamantane to change the distribution of a drug [10]. The conjugation of an adamantyl group as a "lipophilic carrier" allows poorly absorbed drugs to penetrate the BBB more readily and increase the concentration in the brain tissue.
^Vernier VG, du Pont EI (1974). "Chapter 3. Antiparkinsonism Drugs". Annual Reports in Medicinal Chemistry. Vol. 9. Elsevier. pp. 19–26. doi:10.1016/s0065-7743(08)61424-4. ISBN978-0-12-040509-1. Carmantadine (VII, Sch 15427) is structurally related to amantadine33. It shares some of its pharmacological actions, was effective in a head-turning test34, and is in early clinical trials. Dopamantine (VIII) combined elements of both amantadine and dopamine in its structure, shares some pharmacological effects of amantadine and is in early clinical trials35.
^Thorré, Katrien; Sarre, S.; Twahirwa, E.; Meeusen, R.; Ebinger, G.; Haemers, A.; Michotte, Y. (1996). "Effect of l-tryptophan, l-5-hydroxytryptophan and l-tryptophan prodrugs on the extracellular levels of 5-HT and 5-HIAA in the hippocampus of the rat using microdialysis". European Journal of Pharmaceutical Sciences. 4 (4): 247–256. doi:10.1016/0928-0987(95)00056-9.
^ abKozlenkov, Alexey; González-Maeso, Javier (2013). "Animal Models and Hallucinogenic Drugs". The Neuroscience of Hallucinations. New York, NY: Springer New York. pp. 253–277. doi:10.1007/978-1-4614-4121-2_14. ISBN978-1-4614-4120-5.
^Carbonaro TM, Gatch MB (September 2016). "Neuropharmacology of N,N-dimethyltryptamine". Brain Res Bull. 126 (Pt 1): 74–88. doi:10.1016/j.brainresbull.2016.04.016. PMC5048497. PMID27126737. Endogenous DMT is synthesized from the essential amino acid tryptophan, which is decarboxylated to tryptamine. Tryptamine is then transmethylated by the enzyme indolethylamine-N-methyltransferase (INMT) (using S-adenosyl methionine as a substrate), which catalyzes the addition of methyl groups resulting in the production of N-methyltryptamine (NMT) and DMT. NMT can also act as a substrate for INMT-dependent DMT biosynthesis (Barker et al., 1981).
^Barker SA (2018). "N, N-Dimethyltryptamine (DMT), an Endogenous Hallucinogen: Past, Present, and Future Research to Determine Its Role and Function". Front Neurosci. 12: 536. doi:10.3389/fnins.2018.00536. PMC6088236. PMID30127713. After the discovery of an indole-N-methyl transferase (INMT; Axelrod, 1961) in rat brain, researchers were soon examining whether the conversion of tryptophan (2, Figure 2) to tryptamine (TA; 3, Figure 2) could be converted to DMT in the brain and other tissues from several mammalian species. Numerous studies subsequently demonstrated the biosynthesis of DMT in mammalian tissue preparations in vitro and in vivo (Saavedra and Axelrod, 1972; Saavedra et al., 1973). In 1972, Juan Saavedra and Julius Axelrod reported that intracisternally administered TA was converted to N-methyltryptamine (NMT; 4, Figure 2) and DMT in the rat, the first demonstration of DMT's formation by brain tissue in vivo.
^Cameron LP, Olson DE (October 2018). "Dark Classics in Chemical Neuroscience: N, N-Dimethyltryptamine (DMT)"(PDF). ACS Chem Neurosci. 9 (10): 2344–2357. doi:10.1021/acschemneuro.8b00101. PMID30036036. Like serotonin and melatonin, DMT is a product of tryptophan metabolism.25 Following tryptophan decarboxylation, tryptamine is methylated by an N-methyltransferase (i.e., INMT) with S-adenosylmethionine serving as the methyl donor. A second enzymatic methylation produces DMT (Figure 3A).26 [...] The enzyme indolethylamine N-methyltransferase (INMT) catalyzes the methylation of a variety of biogenic amines, and is responsible for converting tryptamine into DMT in mammals.140
^Colosimo, Frankie A.; Borsellino, Philip; Krider, Reese I.; Marquez, Raul E.; Vida, Thomas A. (26 February 2024). "The Clinical Potential of Dimethyltryptamine: Breakthroughs into the Other Side of Mental Illness, Neurodegeneration, and Consciousness". Psychoactives. 3 (1). MDPI AG: 93–122. doi:10.3390/psychoactives3010007. ISSN2813-1851. The metabolism of DMT within the body begins with its synthesis. Endogenous DMT is made from tryptophan after decarboxylation transforms it into tryptamine [22,25]. Tryptamine then undergoes transmethylation mediated by indolethylamine-N-methyltransferase (INMT) with S-adenosyl methionine (SAM) as a substrate, morphing into N-methyltryptamine (NMT) and eventually producing N,N-DMT [26]. Intriguingly, INMT is distributed widely across the body, predominantly in the lungs, thyroid, and adrenal glands, with a dense presence in the anterior horn of the spinal cord. Within the cerebral domain, regions such as the uncus, medulla, amygdala, frontal cortex, fronto-parietal lobe, and temporal lobe exhibit INMT activity, primarily localized in the soma [26]. INMT transcripts are found in specific brain regions, including the cerebral cortex, pineal gland, and choroid plexus, in both rats and humans. Although the rat brain is capable of synthesizing and releasing DMT at concentrations similar to established monoamine neurotransmitters like serotonin [27], the possibility that DMT is an authentic neurotransmitter is still speculative. This issue has been controversial for decades [28] and requires the demonstration of an activity-dependent release (i.e., Ca2+-stimulated) of DMT at a synaptic cleft to be fully established in the human brain.
^Schmid, Cullen L.; Bohn, Laura M. (2018). "βArrestins: Ligand-Directed Regulators of 5-HT2A Receptor Trafficking and Signaling Events". 5-HT2A Receptors in the Central Nervous System. Cham: Springer International Publishing. pp. 31–55. doi:10.1007/978-3-319-70474-6_2. ISBN978-3-319-70472-2.
^Glennon RA, Rosecrans JA (1981). "Speculations on the mechanism of action of hallucinogenic indolealkylamines". Neurosci Biobehav Rev. 5 (2): 197–207. doi:10.1016/0149-7634(81)90002-6. PMID7022271.
^Sourkes TL (1991). "Alpha-methyltryptophan as a therapeutic agent". Prog Neuropsychopharmacol Biol Psychiatry. 15 (6): 935–938. doi:10.1016/0278-5846(91)90020-2. PMID1763198.
^Santillo MF, Sprando RL (April 2023). "Picamilon, a γ-aminobutyric acid (GABA) analogue and marketed nootropic, is inactive against 50 biological targets". Basic Clin Pharmacol Toxicol. 132 (4): 355–358. doi:10.1111/bcpt.13836. PMID36668678.
^Bianchi M, Quadro G, Mourier G, Galzigna L (1983). "Pharmacokinetics and in vitro effects of a 4-aminobutyric acid derivative with anticonvulsant action". Pharmacology. 27 (4): 237–240. doi:10.1159/000137876. PMID6634934.
^ abStorer, R. James; Ferrante, Antonio (10 October 1997). "Radiochemical Assay of Diamine Oxidase". Polyamine Protocols. Methods in Molecular Biology. Vol. 79. New Jersey: Humana Press. pp. 91–96. doi:10.1385/0-89603-448-8:91. ISBN978-0-89603-448-8. PMID9463822. In biological mixtures γ-aminobutyraldehyde may be alternatively oxidized by aldehyde dehydrogenases (EC 1.2.1.3) to γ-aminobutyric acid (GABA) (11—13). The formation of 4-amino-1-butanol is also possible through reduction by aldehyde dehydrogenase and/or alcohol dehydrogenase (13,14), thus preventing cyclization. Other fates of putrescine in biological mixtures include the acetylation to acetylputrescine by an N-acetyltransferase and then oxidation by monoamine oxidase (EC 1.4.3.4) (11,17). [...] Fig 1 Fates of putrescine in biological mixtures
^Rashmi, Deo; Zanan, Rahul; John, Sheeba; Khandagale, Kiran; Nadaf, Altafhusain (2018). "γ-Aminobutyric Acid (GABA): Biosynthesis, Role, Commercial Production, and Applications". Studies in Natural Products Chemistry. Vol. 57. Elsevier. pp. 413–452. doi:10.1016/b978-0-444-64057-4.00013-2. ISBN978-0-444-64057-4. Alternate pathways of GABA synthesis from putrescine and other polyamines have also been reported [207–211]. Here, γ-aminobutyraldehyde, an intermediate from polyamine degradation reaction via combined activities of diamine oxidase (DAO, E.C. 1.4.3.6) and 4-aminobutyraldehyde dehydrogenase (ABALDH), leads to the synthesis of GABA [205,212,213]. In response to abiotic stresses, GABA is also reported to be synthesized from proline via D1-pyrroline intermediate formation [47,205,214] and also by a nonenzymatic reaction [214]. However, GABA synthesis from polyamine pathways is minor in the brain, [215] although they play a significant role in the developing brain [216] and retina [217]. But GABA can be formed from putrescine in the mammalian brain [218].
^Benedetti MS, Dostert P (1994). "Contribution of amine oxidases to the metabolism of xenobiotics". Drug Metab Rev. 26 (3): 507–535. doi:10.3109/03602539408998316. PMID7924902. MAO also catalyses the deamination of a natural brain constituent, monoacetyl-putrescine, producing y-acetylaminobutyraldehyde, which in turn participates in the formation of brain GABA [13].
^Parnetti L, Mignini F, Tomassoni D, Traini E, Amenta F (June 2007). "Cholinergic precursors in the treatment of cognitive impairment of vascular origin: ineffective approaches or need for re-evaluation?". J Neurol Sci. 257 (1–2): 264–269. doi:10.1016/j.jns.2007.01.043. PMID17331541.