Norepinephrine, adrenaline from

Dopamine hydroxylase synthesizes norepinephrine (Nor-adrenalin) from dopamine. 

Known most famously for their part in the fight or flight response to a threat, challenge or anger, adrenaline (epinephrine) and dopamine from the adrenal medulla and noradrenaline (norepinephrine), mainly from neurones in the sympathetic nervous system are known collectively as catecholamines. Synthesis follows a relatively simple pathway starting with tyrosine (Figure 4.7). 

Catecholamines. The catecholamines, epinephrine (EPl adrenaline) (85), norepinephrine (NE noradrenaline) (86) (see Epinephrine and norepinephrine), and dopamine (DA) (2), are produced from tyrosine by the sequential formation of L-dopa, DA, NE, and finally EPl. EPl and NE produce their physiological effects via CC- and -adrenoceptors, a-Adrenoceptors can be further divided into CC - and a2-subtypes which in turn are divided... 

Catecholamines are biogenic amines with a catechol (o-dihydroxy-benzol) structure. They are synthesized in nerve endings from tyrosine and include dopamine, noradrenaline (norepinephrine) and adrenaline (epinephrine). 

Synthesis of noradrenaline (norepinephrine) is shown in Figure 4.7. This follows the same route as synthesis of adrenaline (epinephrine) but terminates at noradrenaline (norepinephrine) because parasympathetic neurones lack the phenylethanolamine-N-methyl transferase required to form adrenaline (epinephrine). Acetylcholine is synthesized from acetyl-Co A and choline by the enzyme choline acetyltransferase (CAT). Choline is made available for this reaction by uptake, via specific high-affinity transporters, within the axonal membrane. Following their synthesis, noradrenaline (norepinephrine) or acetylcholine are stored within vesicles. Release from the vesicle occurs when the incoming nerve impulse causes an influx of calcium ions resulting in exocytosis of the neurotransmitter. 

In contrast, much is known about the catabolism of catecholamines. Adrenaline (epinephrine) released into the plasma to act as a classical hormone and noradrenaline (norepinephrine) from the parasympathetic nerves are substrates for two important enzymes monoamine oxidase (MAO) found in the mitochondria of sympathetic neurones and the more widely distributed catechol-O-methyl transferase (COMT). Noradrenaline (norepinephrine) undergoes re-uptake from the synaptic cleft by high-affrnity transporters and once within the neurone may be stored within vesicles for reuse or subjected to oxidative decarboxylation by MAO. Dopamine and serotonin are also substrates for MAO and are therefore catabolized in a similar fashion to adrenaline (epinephrine) and noradrenaline (norepinephrine), the final products being homo-vanillic acid (HVA) and 5-hydroxyindoleacetic acid (5HIAA) respectively. 

In addition to their well known role in protein structure, amino acids also act as precursors to a number of other important biological molecules. For example, the synthesis of haem (see also Section 5.3.1), which occurs in, among other tissues, the liver begins with glycine and succinyl-CoA. The amino acid tyrosine which maybe produced in the liver from metabolism of phenylalanine is the precursor of thyroid hormones, melanin, adrenaline (epinephrine), noradrenaline (norepinephrine) and dopamine. The biosynthesis of some of these signalling molecules is described in Section 4.4. 

Tyrosine (Tyr or Y) (4-hydroxyphenylalanine ((5)-2-amino-3-(4-hydroxyphenyl)-propanoic acid)) is a polar, neutral, aromatic amino acid with the formula H00CCH(NH2)CH2C6H50H and is the precursor of thyroxin, dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), and the pigment melanin. Being the precursor amino acid for the thyroid gland hormone thyroxin, a defect in this may result in hypothyroidism. Tyr is extremely soluble in water, a property that has proven useful in isolating this amino acid from protein hydrolysates. The occurrence of tyrosine- 0-sulfate as a constituent of human urine and fibrinogen has been reported. ... 

Ebstein R, Belmaker R, Grunhaus L, et al Lithium inhibition of adrenaline-stimulated adenylate cyclase in humans. Nature 259 411-413, 1976 Ebstein RP, Hermoni M, Belmaker RH The effect of lithium on noradrenahne-in-duced cyclic AMP accumulation in rat brain inhibition after chronic treatment and absence of supersensitivity. J Pharmacol Exp Ther 213 161-167, 1980 Ebstein RP, Lerer B, Shlaufman M, et al The effect of repeated electroconvulsive shock treatment and chronic lithium feeding on the release of norepinephrine from rat cortical vesicular preparations. Cell Mol Neurobiol 3 191-201, 1983 Ebstein RP, Moscovich D, Zeevi S, et al Effect of lithium in vitro and after chronic treatment on human platelet adenylate cyclase activity prosreceptor modification or second messenger signal amplification. Psychiatry Res 21 221-228, 1987 Eccleston D, Cole AJ Calcium-channel blockade and depressive illness. Br J Psychiatry 156 889-891, 1990... 

The bronchi have a rich parasympathetic innervation but there is no sympathetic innervation of bronchial smooth muscle and all sympathetic effects are due to circulating adrenaline (epinephrine and noradrenaline (norepinephrine) acting on (32 adrenoceptors. Stimulation of these receptors mediates bronchodilatation by relaxation of bronchial smooth muscle. Beta-adrenoceptor agonists also have limited antiinflammatory actions. They inhibit mediator release from mast cells and may stimulate... 

Catecholamine Hormones The water-soluble compounds epinephrine (adrenaline) and norepinephrine (noradrenaline) are catecholamines, named for the structurally related compound catechol. They are synthesized from tyrosine. 

Two synonyms, two definitions, and an expression of admiration. The word norepinephrine is synonymous with noradrenalin, and the word epinephrine is synonymous with adrenalin. The distinctions are that the first in each case is American and the second British. And the term chiral indicates a potential asymmetry in a molecule that would allow eventual separation into two optical isomers. The term racemic refers to a mixture of these two isomers which has not yet been separated into the individual components. A racemic mixture is called a racemate and, from the point of view of the human animal (which is completely asymmetric), must be considered as a mixture of two structurally identical but... 

Dextroamphetamine stimulates the production of the neurotransmitters dopamine and norepinephrine. Neurotransmitters are the brain chemicals responsible for transporting electrical impulses from nerve cell to nerve cell. Dopamine, the neurotransmitter associated with feelings of pleasure, triggers the euphoria that is related to dextroamphetamine use. Norepinephrine is a neurotransmitter thought to be responsible for the adrenaline-like effects of the drug. 

---