Norepinephrine noradrenaline

FIGURE 27 5 Tyrosine is the biosynthetic precursor to a number of neurotransmit ters Each transformation IS enzyme catalyzed Hydroxy lation of the aromatic ring of tyrosine converts it to 3 4 dihyd roxyphenylalanine (l dopa) decarboxylation of which gives dopamine Hy droxylation of the benzylic carbon of dopamine con verts It to norepinephrine (noradrenaline) and methy lation of the ammo group of norepinephrine yields epi nephrine (adrenaline)... 

Adrenergic. Relating to epinephrine (adrenaline) or norepinephrine (noradrenaline). Commonly used to describe neurons that utilize norepinephrine as a neurotransmitter and the drugs that interact with these neurons. 

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. ... 

Tyrosine is also the metabolic precursor to the neurotransmitter dopamine and the catecholamine hormones norepinephrine (noradrenaline) and epinephrine (adrenaline), as well as to the alkaloids in opium, including morphine. 

Methylations are catalyzed by a family of relatively specific methyl-transferases involving the transfer of methyl groups to hydroxyl groups (0-methylation as in norepinephrine [noradrenaline]) or to amino groups (N-methylation of norepinephrine, histamine, or serotonin). 

The adrenal gland and adrenergic neurons continue the synthesis by hydroxylating dopamine into norepinephrine (noradrenaline). Ascorbic acid (vitamin C see p.368) acts as a hydrogen-transferring coenzyme here. 

Despite the fact that the initial biochemical abnormalities responsible for depression and manic-depressive conditions have not been completely discovered, some facts suggest that depressive conditions may be caused by a lack of norepinephrine (noradrenaline) and serotonin. The majority of drugs used in treatment of such illnesses act by affecting the system of biogenic amines of the brain, thus leading to action of a mechanism that is capable of increasing their contents in respective parts of the brain. 

It is believed that tricyclic antidepressants inhibit the (neuronal) reuptake of norepinephrine (noradrenaline) and/or serotonin by presynaptic nerve endings, thus blocking one of the leading mechanisms of their inactivation, and thereby increasing the concentration of the indicated amines potentiating their effects. It should be noted that, as a rule, secondary amines, which are representatives of tricyclic antidepressants, exhibit high activity, blocking the neuronal reuptake of norepinephrine, while tertiary amines act more on the neuronal reuptake of serotonin. 

Monoaminooxidase is a complex enzymatic system that is present in practically every organ that catalyzes deamination or inactivation of various natural, biogenic amines, in particular norepinephrine (noradrenaline), epinephrine (adrenaline), and serotonin. Inhibition of MAO increases the quantity of these biogenic amines in nerve endings. MAO inhibitors increase the intercellular concentration of endogenous amines by inhibiting then-deamination, which seems to be the cause of their antidepressant action. 

Together with the CNS, compounds of this group affect the nervous system. They indirectly stimulate a- and fi- adrenoreceptors. The adrenomimetic properties of these compounds are similar to the properties of norepinephrine (noradrenaline) however, they are quite inferior to them in terms of activity. 

In terms of chemical structure, amphetamines are very close to epinephrine (adrenaline), norepinephrine (noradrenaline), and dopamine, differing in the absence of a hydroxyl group in the aromatic ring and in the aliphatic chain. 

Adrenergic drugs are natural or synthetic compounds that either partially or completely replicate the effects of norepinephrine (noradrenaline), epinephrine (adrenaline), and dopamine, and which cause a biological response similar to the activation of the sympathetic nervous system. They are also referred to as sympathomimeties beeause they mimic the stimulation of the sympathetic nervous system. 

In general, the response of effector organs to epinephrine (adrenahne) and/or norepinephrine (noradrenaline) is directly determined by the type of adrenoreceptor, as well as by the ratio of a- and )3-adrenoreceptors. 

Deficiency of this coenzyme can lead to many manifestations. Clinical signs include retarded growth, acrodynia, alopecia, skeletal changes and anemia, while changes in neurotransmitters, such as dopamine, serotonin, norepinephrine (noradrenaline), tryptamine, tyramine, histamine, y-aminobutyric acid, and taurine, affect the brain function and can lead to seizures and convulsions. An overdose of vitamin Bg leads to neuronal damage and sensory and motor effects [417],... 

Depending on the drug and its form, CNS stimulants are usually taken either orally as a solid or tea or by the chewing of leaves, by injection, by smoking, or by snorting. Injection directly into the bloodstream or inhalation of smoke into the lungs induces a very rapid onset of action. CNS stimulants induce their effects by increasing the synaptic concentrations of several neurotransmitters, particularly norepinephrine (noradrenaline), dopamine, and serotonin. They stimulate the release of neurotransmitters and block their reuptake. 

Barbiturates, benzodiazepines, and GHB affect the activity of the neurotransmitter GABA, resulting in more chloride ions entering the neuron and making it more resistant to excitation. As a consequence, the output of excitatory neurotransmitters, including norepinephrine (noradrenaline), serotonin, and dopamine, is reduced. 

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. 

Noncompetitive inhibition 476,477 Nonheme iron proteins. See Iron-sulfur and diiron proteins Nonlinear equations 460 Nonmetallic ions, ionic radii, table 310 Nonproductive complexes 475 Norepinephrine (noradrenaline) 553,553s in receptor 555s Nuclear envelope 11... 

Norepinephrine (noradrenalin) Tyrosine derivative (see fig. 24.10) Arteriole contraction, lipid release... 

In this chapter, we have looked at two topics in cognitive enhancement attention and memory. We have first reviewed the role of dopamine and norepinephrine/ noradrenaline in the neuropharmacology of attention, and then the syndrome of attention deficit disorder as a common problem associated with a disorder of attention. We then discussed the use of stimulants for improving attention, primarily in attention deficit disorder, and reviewed the pharmacological mechanisms of action of methylphenidate, d and 1 amphetamine, pemoline, and secondary therapies such as clonidine and guanfacine. 

The second section on clinical science has been increased by two chapters to accommodate the increase in the numbers of drugs and advances in knowledge about psychiatric disorders. Three new neurotransmitter systems are introduced and illustrated substance P and the neurokinin family nitric oxide and the endocannabi-noids such as anandamide (the brain s own marijuana ). Also amplified is coverage of the classical neurotransmitter systems, especially intercommunications now illustrated between serotonin and dopamine and between norepinephrine/noradrenaline and serotonin. Also included are numerous new illustrations of noradrenergic and cholinergic pathways. 

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