Catecholamines noradrenaline

Hi-receptors in the adrenal medulla stimulates the release of the two catecholamines noradrenaline and adrenaline as well as enkephalins. In the heart, histamine produces negative inotropic effects via Hr receptor stimulation, but these are normally masked by the positive effects of H2-receptor stimulation on heart rate and force of contraction. Histamine Hi-receptors are widely distributed in human brain and highest densities are found in neocortex, hippocampus, nucleus accumbens, thalamus and posterior hypothalamus where they predominantly excite neuronal activity. Histamine Hrreceptor stimulation can also activate peripheral sensory nerve endings leading to itching and a surrounding vasodilatation ( flare ) due to an axonal reflex and the consequent release of peptide neurotransmitters from collateral nerve endings. 

The effects of the amphetamines are discussed in detail in Chapter 7 and are thought to be due to changes in the catecholamines, noradrenaline and dopamine. The peripheral... 

Figure 1-1 shows an example of the detection limits that can be reached with EC detection. The chromatogram shows the separation and detection of the catecholamines noradrenaline (nor), adrenaline (adr), dihydroxybenzylamine (dhba), and dopamine (dopa), using a glassy carbon electrode at a working potential of +0.6 V. The minimum detectable quantity is less than 3 Pg-... 

Much attention has been paid to the catecholamines noradrenaline and dopamine following the discovery that their depletion in the brain leads to profound mood changes and locomotor deficits. Thus noradrenaline has been implicated in the mood changes associated with mania and depression, while an excess of dopamine has been implicated in schizophrenia and a deficit in Parkinson s disease. 

The catecholamines noradrenaline (norepinephrine) and adrenaline (epinephrine) are amines derived via decarboxylation of amino acids. Noradrenaline is a mammalian neurotransmitter, and adrenaline, the... 

The neurotransmitters of the sympathetic nervous system are the catecholamines noradrenaline (mainly in the nerve terminals of peripheral nerves and in the central nervous system), adrenaline (mainly in the adrenal medulla) which has to reach the target organs with the blood stream and dopamine. 

O -Adrenoceptor antagonists (o -blockers) are competitive inhibitors at the level of Q -adrenoceptors. These receptors are found in many organs and tissues, but their predominant functional importance is to mediate the vasoconstrictor effects of endogenous catecholamines (noradrenaline, adrenaline) released from the sympathetic nerve endings. Conversely, Q -adrenoceptor antagonism by means of an a-blocker will inhibit this constrictor activity and hence cause vasodilatation. This vasodilator effect occurs in both resistance vessels (arterioles) and capacitance vessels (veins), since a-adrenoceptors are present in both types of vascular structures. Accordingly, both cardiac afterload and preload will be lowered, in particular when elevated. 

Adrenoceptors of the /3-subtype are important mediators of the sympathetic activation of the heart, kidney, and bronchi. /3-Adrenoceptors are also found in other organs and tissues such as blood vessels and the central nervous system. Accordingly, /3-adrenoceptor antagonists or jS-blockers inhibit the stimulating influence of the endogenous catecholamines (noradrenaline, adrenaline) on the various organs and tissues which are subject to sympathetic innervation. In cardiovascular medicine the /3-blockers are used in particular to blunt the sympathetic activation of the heart and kidneys. These effects are mediated by the /3i-subtype of the /3-adrenoceptors. The currently used /3-blockers are all competitive antagonists of the /3i-adrenoceptor, which is the basis of their therapeutic application. 

Dopamine -hydroxylase is a copper-containing enzyme involved in the synthesis of the catecholamines noradrenaline and adrenaline from tyrosine in the adrenal medulla and central nervous system (see Figure 13.4). The active enzyme contains Cu+, which is oxidized to Cu + during the hydroxylation of the substrate. Reduction back to Cu+ specifically requires ascorbate, which is oxidized to monodehydroascorbate. 

Neurotransmitters serve to transmit signals between neurons, which are separated by a synaptic cleft. One of the neurotransmitters is dopamine (DA), or P-(3,4-dihydroxyphenyl)ethylamine (1). Until the mid-1950s dopamine was exclusively considered to be an intermediate in the biosynthesis of the catecholamines noradrenaline and adrenaline. Significant tissue levels of dopamine were first demonstrated in peripheral organs of ruminant species.1 A short time later it was found that dopamine was also present in the brain in about equal concentrations to those of noradrenaline.2... 

Documented effects An extract of this herb sharply iuCTeases blood pressure, due to its high noradrenaline content. Hemostatic action for internal hemorrhaging has been documented (Khalmatov 1964). In experiments with mice and rats, an ethanolic extract of the dried aboveground parts showed significant antiinflammatory and analgesic effects after intra-peritoneal and topical, but not oral, administration (Chan et al. 2000). Studies indicated that the consumption of the plant may help to reduce the occurrence of cancer and heart diseases. Catecholamines (noradrenaline and dopamine) contained in the plant are generally considered to be the effective component in the treatment of shock. Studies have also shown that noradrenaline is a modulator of the immune system and may have anti-cancer properties (Chen et al. 2003). 

Tabie8.1 RelativeGlobalEn ors(%)in the Prediction ofRetentionFactors forFive Catecholamines (Noradrenaline, Adrenaline, Adrenalone,... 

Calculated k values according to eq. 8.26 and design VI (Fig. 8.4) are plotted in Fig. 8.8, against experimental values, for (i) five catecholamines (noradrenaline, adrenaline, adrenalone, dopamine, and isoprenaline) and thirteen mobile phases (0.035-0.150 M SDS and 0-15% 1-propanol), (ii) fifteen phenols (4-benzamidephenol, 4-hydroxy-benzyl alcohol, 4-hydroxyphenemethyl alcohol, 4-hydroxybenzyl cyanide, 4-hydroxyacetophenone, 4-hydro2 benzaldehyde, phenol, 4-fluorophenol, 4-... 

Another catecholamine, noradrenaline, is produced mainly at the nerve endings of the sympathetic system and also in small amounts in the adrenal medulla. Secretion from this gland appears to be under nervous control and occurs rapidly as an appropriate response to stressful situations. 

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