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Summation of Basic Endocrine Data
Published in George H. Gass, Harold M. Kaplan, Handbook of Endocrinology, 2020
The medulla produces two major hormones, epinephrine and norepinephrine. These are called catecholamines and are biogenic amines. The term “catecholamine” stems from the fact that these substances contain catechol (ortho-dihydroxybenzene) and a side chain with an amino group.
Neural Control of Adenohypophysis
Published in Paul V. Malven, Mammalian Neuroendocrinology, 2019
Besides hypothalamic peptides, a group of compounds known as monoamines participate directly or indirectly in the hypothalamic regulation of the adenohypophysis. Figure 4-2 shows the chemical structures of the three most important monoamines that regulate, directly or indirectly, the adenohypophysis. The structures of dopamine and norepinephrine are very similar, differing only by one hydroxyl group. Both compounds are known as catecholamines because of the six-membered catechol ring structure. Serotonin is known as an indolamine because of its unique double-ring structure. All three monoamines in Figure 4-2 share the single amine group from which the monoamine terminology is derived. Techniques to stain for monoamines actually preceded the immunocytochemical staining of peptides because the chemical nature of the hypothalamic RF had not yet been discovered. This staining was based on histochemical fluorescence of the catecholamines and indolamines after specific chemical treatments. These monoamines were also quantified in dissected tissues using chemical assays.
Drug Targeting to the Lung: Chemical and Biochemical Considerations
Published in Anthony J. Hickey, Sandro R.P. da Rocha, Pharmaceutical Inhalation Aerosol Technology, 2019
Peter A. Crooks, Narsimha R. Penthala, Abeer M. Al-Ghananeem
Most of the research centered on the targeting of drugs by the prodrug approach has been carried out on β2 stimulants structurally related to isoproterenol and similar drugs. The basic approach has been to esterify the catechol functions of isoproterenol to achieve better uptake in lung tissues of the resulting inactive lipophilic drug, which may then be metabolically cleaved by lung esterases to release the active parent compound (Hussain and Truelove 1975, Shargel and Dorrbecker 1976). In addition, esterification of the catechol function acts to protect the drug from deactivation by metabolic conjugation. The elimination of cardiovascular side effects using this approach depends on the preferential uptake of the prodrug by the lung and the greater esterase activity in lung tissue relative to heart tissue. However, a prolonged therapeutic effect may also be obtained simply by increasing drug residence time in the body through reduced renal clearance. This can be achieved by conjugation of the drug to form a lipophilic prodrug containing a slowly hydrolysable linker group (e.g. a carbamate) (Olsson and Svensson 1984).
Alpha-synuclein in Parkinson's disease: a villain or tragic hero? A critical view of the formation of α-synuclein aggregates induced by dopamine metabolites and viral infection
Published in Expert Review of Neurotherapeutics, 2023
Phelippe Carmo-Gonçalves, Eduardo Coelho-Cerqueira, Vanderlei de Araujo Lima, Cristian Follmer
DA and other neurotransmitters such as epinephrine and norepinephrine are classified as catecholamines due to the presence of the catechol (1,2-dihydroxybenzene) and amino (NH2) groups, whose combined properties become essential for the reactivity of these molecules in aqueous medium. DA undergoes oxidation in aerated aqueous solution resulting in the formation of DA ortho-quinone (DAQ), aminochrome, and 5,6-indolequinone, which typically polymerize to form a dark pigment, neuromelanin [40]. DAQ undergoes cyclization due to the presence of the amino group forming the stable derivative aminochrome (Figure 1), which exhibits toxicity in mesencephalic neurons through the induction of caspase-independent apoptosis [41]. Aminochrome can be reduced in the presence of either NADH or NADPH, producing highly reactive o-semiquinone radicals (Figure 1). The decrease in NADH levels due to reaction with aminochrome might also lead to disruption of cellular energy metabolism [42]. Furthermore, NADH and NADPH are essential for the catalytic activity of several enzymes, including the aldehyde dehydrogenase (ALDH), which degrades cytotoxic aldehydes. In this context, dopaminergic neurons would present an intrinsic high vulnerability to oxidative stress mediated by DA metabolites, notably by DAQ and/or aminochrome.
A potential paradigm shift in opioid crisis management: The role of pharmacogenomics
Published in The World Journal of Biological Psychiatry, 2022
David Eapen-John, Ayeshah G. Mohiuddin, James L. Kennedy
As mentioned before, dopamine released by VTA neurons into the NAcc reinforces behaviours deemed ‘rewarding’ and produces a feeling of euphoria. Dopamine receptors are classified as D1-like and D2-like. D1-like receptors include DRD1 and DRD5. These receptors increase cAMP and activate the intracellular signalling cascade while the D2-like receptors (DRD2, DRD3, and DRD4), inhibit this process (Jalabert et al. 2011; Zhu et al. 2013; Clarke et al. 2014; Jing Li et al. 2018; Burns et al. 2019). Dopamine levels are regulated in the brain by catechol-O-methyltransferase (COMT) through the degradation of catecholamines including dopamine and norepinephrine. Some studies suggest that DRD1 and DRD2 modulate opioid reinforcement, reward, and opioid-induced neuroadaptation (Clarke et al. 2014; Burns et al. 2019).
Tissue and interspecies comparison of catechol-O-methyltransferase mediated catalysis of 6-O-methylation of esculetin to scopoletin and its inhibition by entacapone and tolcapone
Published in Xenobiotica, 2021
Aaro Jalkanen, Veera Lassheikki, Tommi Torsti, Elham Gharib, Marko Lehtonen, Risto O. Juvonen
Catechol is an important chemical structural motif with multiple cellular functions. The catechol core structure consists of a benzene ring with two adjacent hydroxyl substituents. Humans are exposed to various types of endogenous and exogenous catechol compounds (Riishede and Nielsen-Kudsk 1990; Lekse et al.2001; Cavalieri et al.2006). Endogenous catechol compounds include 3,4-dihydroxytyrosine, catecholamines, their metabolites, catechol estrogens, and dihydroxyindole. Three catecholamines, i.e. dopamine, noradrenaline, and adrenaline, are synthesised from L-dopa, which is the product of the tyrosine hydroxylase oxidation of the amino acid, tyrosine. The catechol estrogens are CYP enzyme oxidisation products of estrogens such as estradiol, estrone, and estriol. Humans are also exposed to exogenous catechol compounds e.g. from therapeutic drugs containing the catechol moiety or from plant sources; in the latter, they protect the plant against UV-light, oxidants, herbivores, and microbes. Drugs containing the catechol core structure include isoprenaline, dobutamine, levodopa, droxidopa, benserazide, entacapone, tolcapone, and nitecapone. Phenolic drugs or other xenobiotics may be oxidised by CYPs to catechol compounds, as exemplified by traxoprodil (Johnson et al.2003) and duloxetine (Lantz et al.2003). Furthermore, plant constituents containing the catechol core structure include verbascoside (Reid et al.2019) and polyphenols such as tannins (Bianco and Savolainen 1994), catechins (Rhodes et al.2013), and flavonoids (Sak 2017).