Catecholamines dopamine norepinephrine serotonin

Other important nitrogen-containing compounds made from amino acids include the catecholamines (dopamine, norepinephrine, and epinephrine), which are synthesized from tyrosine creatine, which is synthesized from arginine and glycine histamine, which is synthesized from histidine and serotonin, which is synthesized from tryptophan. 

Antidepressants were developed in the 1950s. Iproniazid, an agent used to treat tuberculosis, was inadvertently found to produce an improvement in mood. Ultimately, it was discovered to be an inhibitor of monoamine oxidase (MAO)—an enzyme used to break down catecholamines (dopamine, norepinephrine, and serotonin) in neurons. This led to the development of an entire class of antidepressants the monoamine oxidase inhibitors or MAOIs. 

Among the most important neurotransmitters are acetylcholine (ACh), amino acids and their derivatives, and certain polypeptides known as neuropeptides. In fact, the mammalian nervous system is said to employ over 30 different substances as neurotransmitters. For the record, among the amino acids and their derivatives (called biogenic amines) are many that are also hormonally active in the bloodstream, and include the catecholamines dopamine, norepinephrine, and epinephrine, as derived sequentially from tyrosine, whereas y-aminobutyric acid (GABA), histamine, and serotonin are derived from glutamate, histidine, and tryptophan, respectively. The subject interfaces with the biochemical aspects of psychology, which may also be referred to as the mind-body connection, or psychosomatics. 

Catecholamines (dopamine, norepinephrine), opioid peptides, and serotonin act as neurotransmitters in nonspecific or diffuse neuronal systems. Glutamate is the primary excitatory transmitter in hierarchical neuronal systems. The answer is (B). 

There is clear biochemical and clinical heterogeneity between these conditions, but the small number of reported cases precludes an accurate ascertainment of intra-disease heterogeneity. Lack of TH leads to a specific deficit of the catecholamines (dopamine, norepinephrine and adrenaline). AADC is required for the synthesis of the catecholamines and serotonin. Lack of this enzyme therefore causes a global deficiency of all of these neurotransmitters as is found in the abnormalities of tetrahydrobiopterin metabolism (Chap. 1). The clinical symptoms are also similar, including developmental delay, central and peripheral hypotonia, temperature instability, chorea, ptosis and oculogyric crises. The two conditions are in general distinguishable as hyperphenylalaninemia is not present in AADC deficiency. However, certain forms of tetrahydrobiopterin deficiency also do not present with hyperphenylalaninemia. 

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. 

Histamine, serotonin, melatonin, and the catecholamines dopa, dopamine, norepinephrine, and epinephrine are known as "biogenic amines."They are produced from amino acids by decarboxylation and usually act not only as hormones, but also as neurotransmitters. 

Reserpine causes a breakdown of norepinephrine, dopamine, and serotonin in neuron endings. It weakens intracellular uptake of biogenic amines and reduces the ability if storing them in vesicles. It is possible that reserpine acts on membrane vesicles, irreversibly inhibiting ATP-Mg (adenosinetriphosphate) requiring process that is responsible for the uptake of biogenic amines in intemeuronal vesicles. Breakdown of catecholamines is expressed by a decreased number of intraneuronal serotonin and dopamine. 

Monoamine oxidases (MAOs) are involved in the metabohsm of catecholamine and serotonin neurotransmitters such as dopamine, norepinephrine, and epinephrine. 

Another naturally occurring drug that is similar to amphetamine can be found in the cactus Lophophora williamsii. Extracts are used to prepare a drink called peyote that contains 3,4,5-trimethoxyphenyl-ethylamine(the meth and phenyl point to a molecule that is quite lipid soluble). Known as mescaline, this compound is structurally similar to the catecholamines dopamine and norepinephrine but seems to act more directly upon serotonin receptors because of the presence of the meth-oxy groups on the molecule. This feature of the compound s structure would make the compound more fat-soluble and therefore better able to enter the brain quickly and may explain... 

The principal groups of antidepressants available today are all presumed to exert their action via alteration of brain monoamine metabolism. These amines include norepinephrine, dopamine, and serotonin. The involvement of catecholamines in the pathogenesis of depression was invoked as early as 1965. A deficiency in brain serotonin was theorized in 1967, while a role for dopamine in depression was formally proposed in 1975. The drugs that are used to treat depression basically act to increase neurotransmitter concentration in the synaptic cleft either by (1) decreasing neurotransmitter degradation or (2) inhibiting neurotransmitter reuptake. 

Histamine, serotonin and the catecholamines (dopamine, epinephrine and norepinephrine) are synthesized from the aromatic amino acids histidine, tryptophan and phenylalanine, respectively. The biosynthesis of catecholamines in adrenal medulla cells and catecholamine-secreting neurons can be simply summarized as follows [the enzyme catalysing the reaction and the key additional reagents are in square brackets] phenylalanine — tyrosine [via liver phenylalanine hydroxylase + tetrahydrobiopterin] —> i.-dopa (l.-dihydroxyphenylalanine) [via tyrosine hydroxylase + tetrahydrobiopterin] —> dopamine (dihydroxyphenylethylamine) [via dopa decarboxylase + pyridoxal phosphate] — norepinephrine (2-hydroxydopamine) [via dopamine [J-hydroxylasc + ascorbate] —> epinephrine (jV-methyl norepinephrine) [via phenylethanolamine jV-methyltransferase + S-adenosylmethionine]. 

Catecholamine—Monoamines such as the neurotransmitters norepinephrine, serotonin, and dopamine that are synthesized from the amino acid, tyrosine, and have similar structures. Conditioned reflex—response in which one stimulus, the conditioned one, is associated with and elicits the same response as another stimulus, the unconditioned stimulus. 

Monamine oxidase— An enzyme found in the brain and liver which breaks down catecholamines such as norepinephrine, serotonin and dopamine. 

The antidepressants, generally, produce their therapeutic effects by blocking the reuptake of one or more catecholamines (norepinephrine, serotonin, and dopamine), which leads to a decrease (down-regulation) of the number of post-synaptic receptors—generally within seven to twenty-one days, coinciding with the onset of clinical effect (see chapter 3). The MAOIs block monoamine oxidase, which metabolizes the catecholamines stored at the nerve ending of the presynaptic neuron—thereby making more catecholamine available. Stimulants increase the release of catecholamines. Buspirone is a 5-HT lA receptor blocker. 

The effects of amphetamines are due to the increase of neurotransmitters norepinephrine, serotonin, and dopamine in central synapses. This increase is from increased release and reuptake blockade of catecholamines. Amphetamines may also inhibit monoamine oxidase. These mechanisms combine to produce the sympathomimetic and central nervous system (CNS) effects seen with amphetamine abuse. 

Monoamines Biogenic amines with a single amine (an organic compound), this group includes dopamine, norepinephrine, epinephrine (the catecholamines), acetylcholine (quaternary amine), and serotonin (an indoleamine). 

Neurotransmitters are chemicals that carry messages, or signals, from a nerve cell to a target cell, which may be another nerve cell or a muscle cell. They may be inhibitory or excitatory and all are nitrogen-containing compounds. The catecholamines include dopamine, norepinephrine, and epinephrine. Too little dopamine results in Rarkinson s disease. Too much is associated with schizophrenia. Dopamine is also associated with addictive behavior. A deficiency of serotonin is associated with depression and eating disorders. Serotonin is involved in pain perception, regulation of body temperature, and sleep. Histamine contributes to al-... 

Assay of phenylalanine hydroxylase in a liver biopsy from one patient showed 20% of normal adult control values, but dihydropteridine reductase activity (Fig. 20.2) was less than 1% of normal in the liver, brain, and other tissues. This latter deficiency presents regeneration of tetrahydrobiopterin, the cofactor for the hydroxylase reaction. Since the reductase enzyme reaction regenerates the cofactor for tyrosine and tryptophan hydroxylase, catecholamine and serotonin synthesis are compromised as well. Patient studies are scanty, but in one patient dopamine and serotonin were decreased in the cerebrospinal fluid, brain, and various other tissues, while norepinephrine metabolites were normal. While phenylalanine hydroxylase activity was lower than that of adult controls, it was not determined whether this value represented significantly decreased activity in children. 

Other recent reports which indirectly tend to weaken the concept that norepinephrine is the sole alerting neurohumor indicate that (1) imipramine hyperactivity may result from blocking uptake and reducing nervous impulse flow in central serotonin neurons (2) drugs which Inhibit uptake of catecholamines also block serotonin accumulation in rabbit brain stem preparations (3) the increase in overt stimulation caused by 5-hydroxy-tryptophan may be associated with Impaired norepinephrine synthesis rather than increased norepinephrine release and (4) norepinephrine and dopamine inhibit electrical activity of central neurons as determined microelectro-phoretically although another study indicated that norepinephrine does cause neuronal excitation ... 

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