Norepinephrine chemical structure

The chemical structure of histamine has similarities to the structures of other biogenic amines, but important differences also exist. Chemically, histamine is 2-(4-imidazolyl)ethylamine (Fig. 14-1). The ethylamine backbone is a common feature of many of the amine transmitters (e.g. dopamine, norepinephrine and serotonin). However, the imidazole nucleus, absent from other known transmitters, endows histamine with several distinct chemical properties. Among these is prototypic tautomerism, a property that permits it to exist in two different chemical forms (Fig. 14-1). The tautomeric properties of histamine are thought to be critical in the... 

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. 

Pharmacoiogy Nefazodone is an antidepressant with a chemical structure unrelated to available antidepressant agents. The mechanism of action is unknown. Nefazodone inhibits neuronal uptake of serotonin and norepinephrine. Pharmacokinetics ... 

The adrenomimetic drugs can be divided into two major groups on the basis of their chemical structure the catecholamines and the noncatecholamines. The catecholamines include norepinephrine, epinephrine, and dopamine, all of which are naturally occurring, and several synthetic substances, the most important of which is isoproterenol (isopropyl norepinephrine). The skele-... 

TCAs derive their name from their chemical structure aU tricyclics have a three-ring nucleus. Currently, most clinicians are moving away from using TCAs as first-line drugs relative to the newer antidepressants, they tend to have more side effects, to require gradual titration to achieve an adequate antidepressant dose, and to be lethal in overdose. Some data suggest that TCAs may be more effective than SSRIs in the treatment of major depression with melancholic features (Danish University Antidepressant Group 1990 Perry 1996) however, many skilled clinicians and researchers continue to prefer the newer antidepressants, even for patients with melancholia, for the aforementioned reasons. Newer medications that affect both norepinephrine and serotonin (e.g., venlafaxine and mirtazapine) also may have superior efficacy in severely iU depressed patients or when remission is defined as the outcome (Thase et al. 2001). 

Stimulants have chemical structures that are similar to key brain neurotransmitters called monoamines, including dopamine and norepinephrine. Their therapeutic effect is achieved by slow and steady increases of dopamine that are similar to the natural production of this chemical by the brain. The doses prescribed by physicians start low and increase gradually until a therapeutic effect is reached. However, when taken in doses and routes other than those prescribed, stimulants can increase the brain s dopamine levels in a rapid and highly amplified manner—as do most other drugs... 

The chemical structures of the stress neurotransmitter norepinephrine and the maintenance neurotransmitter acetylcholine. 

Fig. 2. Chemical structure of the endogenous catecholamines, epinephrine (8), and norepinephrine (7), and several synthetic phenethanolamines that alter...

The composition of the six controlled substance analogs listed above often stimulate the same areas of the brain, but are chemically quite distinct from one another. MDMA (3, 4-methylenedioxymethampheta-mine) is a complex drug that makes simple classification difficult. Its chemical structure is related both to the stimulant methamphetamine and the hallucinogen mescaline. Methamphetamine bears a close resemblance to two powerful chemicals in the body, dopamine and norepinephrine, which regulate mood, memory, and movement. 

Antidepressants generally fall into one of three categories (1) tricyclic antidepressants (TCAs), which are so named because of their three-ring chemical structure (2) selective serotonin reuptake inhibitors (SSRIs), which block only the reabsorption of serotonin and not of norepinephrine and (3) monoamine oxidase (MAO) inhibitors, which inhibit the metabolic breakdown of norepinephrine and/or serotonin. 

Talopram 58 and citalopram 59 (Figure 2.17) are closely related in their chemical structures. Nevertheless, talopram is a norepinephrine uptake blocker with a selectivity factor of about 550 against serotonin uptake, whereas citalopram is a serotonin uptake blocker, with a selectivity of 3400 against norepinephrine uptake. A similar selectivity difference applies to the even more closely related pair nisoxetine 60, with a norepinephrine uptake selectivity of about 180, and fluoxetine 61 (Figure 2.17), with a serotonin uptake selectivity of 54 [33],... 

Monoamine oxidases (MAO-A and MAO-B) are mitochondrial enzymes that oxidatively deaminate endogenous biogenic amine neurotransmitters such as dopamine, serotonin, norepinephrine, and epinephrine. MAOs are like EMOs in that they catalyze the oxidation of drugs to produce drug metabolites that are identical in chemical structures to those formed by CYPs. Because the resulting structures are... 

Chemical/Pharmaceutical/Other Class Catecholamines are endogenous neurotransmitters or hormones. Dopamine and norepinephrine are in the monoamine class Chemical Structures ... 

Mazindol has a different chemical structure from the phenylethylamine compounds considered above and a somewhat different pharmacological profile. Rather than promoting release of norepinephrine, it inhibits the neuronal reuptake of norepinephrine in the brain. In healthy human subjects a single oral dose of 1 mg reduces food intake significantly more than placebo for a period of eight hours (Silverstone 1982). 

When neurotransmitters are released into the synapse they are either taken up by transporters back into the neuron to be used again or are degraded. Recall that the monoamines serotonin, dopamine, and norepinephrine have similar chemical structures and, as such, they follow the same pathways of synthesis and breakdown. All monoamines are degraded by an enzyme called monoamine oxidase. MAOIs bind irreversibly (i.e., form covalent bonds) to the reactive site of monoamine oxidase. 

Figure 4.2 Effexor (venlafaxine), the chemical structure of which is shown here, is a second generation antidepressant. Effexor blocks the reuptake of both serotonin and norepinephrine. It also has a short half-life (5 hours).

Hormones are transported from the sites of their synthesis to the sites of action by the bloodstream (Figure 24.5). In terms of their chemical structure, some typical hormones are steroids, such as estrogens, androgens, and mineralocorticoids (Section 21.8) polypeptides, such as insulin and endorphins (Section 3.5) and amino acid derivatives, such as epinephrine and norepinephrine (Table 24.3). 

Considering the chemical structure of ephedrine, it is interesting to observe the lack of the phenolic group, characteristic of catecholamines. However, ephedrine remains capable to stimulate a- and p-receptor directly and displace norepinephrine (NE) from storage vesicles, releasing these catecholamines at synaptic areas in the brain and in the heart. These released substances act on receptors promoting the adrenergic effect [17, 66]. 

Ascorbic acid s chemical structure makes it an electron donor and therefore a reducing agent. AA has thus been involved in two different biochemical functions redox/ antioxidant properties and enzymatic cofactor. AA has been demonstrated to be an electron donor for different enzymes. Among these enzymes, three are involved in collagen hydroxylation (Bates et al., 1972 Levene et al., 1972). Two are involved in carnitine synthesis (Nelson et al., 1981 Dunn et al., 1984). The remaining are respectively involved in norepinephrine synthesis (Kuo, 1979) and tyrosine synthesis (La Duand Zannoni, 1964). Deficiency in AA has thus been associated with extracellular matrix defects that are probably involved in vascular problems observed in scurvy. 

Adrenoceptors interact not only with norepinephrine but also with the adrenal medullary hormone epinephrine and a number of chemically related drugs. However, the responses produced by the drugs in different autonomic structures differ quantitatively or qualitatively from one another. 

SNRIs are chemically unrelated to each other. Venlafaxine was discovered in the process of evaluating chemicals that inhibit binding of imipramine. Venlafaxine s in vivo effects are similar to those of imipramine but with a more favorable adverse-effect profile. All SNRIs bind the serotonin (SERT) and norepinephrine (NET) transporters, as do the TCAs. However, unlike the TCAs, the SNRIs do not have much affinity for other receptors. Venlafaxine and desvenlafaxine are bicyclic compounds, whereas duloxetine is a three-ring structure unrelated to the TCAs. Milnacipran contains a cyclopropane ring and is provided as a racemic mixture. 

The renal pressor mechanism—renin and hypertensin—acts in acute hypertension and in acute renal ischemic states, but apparently not in chronic hypertension. The other mechanisms shown to be active in chronic hypertension are vasoexcitor-vasodepres-sor material relationship pherentasin, a pressor substance found only in human hypertension amines resulting from the insufficient oxidation of amino acids, which are increased in human hypertension and norepinephrine (Sympathin E), which largely reproduces the hemodynamic picture of chronic hypertension. Most of the known pressor substances, with the notable exception of norepinephrine, come from disturbances of, or are extracted from, the kidneys. The large number of pressor substances which have been obtained suggests that many may represent different stages of metabolism of certain parent substances, and that their effectors may be fewer in number and simpler in structure. The chemical identification and purification of most of these substances leave much to be desired, and their phafmacology has in most cases been inadequately studied. The whole problem, however, may soon become simplified. 

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