Catecholamine cell groups

Clark FM, Proudfit HK. (1991). Projections of neurons in the ventromedial medulla to pontine catecholamine cell groups involved in the modulation of nociception. Brain Res. 540 105-115. 

Clark, F. M. and Proudfit, H. K. The projection of noradrenergic neurons in the A7 catecholamine cell group to the spinal cord in the rat demonstrated by anterograde tracing combined with immunocytochemistry, Brain Res. 1991b, 547, 279-288. 

Locus Coemleus and Brainstem Catecholamine Cell Groups... 

Refer to Aston-Jones et al. (1995) for the delineation of the locus coeruleus. We delineated the catecholamine cell groups by following Hokfelt etal. (1984) with assistance from our own tyrosine hydroxylase preparations (Paxinos etal, in press [b]). 

Historically, stimulants that increase the activity of catecholamines are the oldest drugs in this group (Jones et al. 1973). Reduction in DA activity has been related to a reduction in wakefulness lesions of DA cell groups in the ventral tegmentum that project to the forebrain have been shown to induce a marked reduction in behavioral arousal in rats (Jones et al. 1973), and patients with Parkinson s disease, who exhibit consistent DA lesions, experience severe sleep disorders (Rye and Jankovic 2002). 

Soulier Y, Dalmaz Y, Cottet-Emard JM, Lagercrautz H, Pequiguot JM. Long-term influence of neonatal hypoxia on catecholamine activity in carotid bodies and brainstem cell groups of the rat. J Physiol 1997 498 523-530. 

Neuropeptide Y is colocalized with catecholamines in the noradrenergic A1 cell group and in the locus ceruleus (94,95). Neuropeptide Y microinjections in the ventrolateral medulla induce hypertensive and bradycardic responses (96) and longterm hypoxia enhances the neuropeptide Y content in the rat ventrolateral medulla. This may be linked to the excitation of a bulbospinal neuropeptide Y sympathoexcitatory system mediating the hypoxia-induced sympathoadrenal activation (97). 

Tyrosine hydroxylase is the rate-limiting enzyme for the biosynthesis of catecholamines. Tyrosine hydroxylase (TH) is found in all cells that synthesize catecholamines and is a mixed-function oxidase that uses molecular oxygen and tyrosine as its substrates and biopterin as its cofactor [1], TH is a homotetramer, each subunit of which has a molecular weight of approximately 60,000. It catalyzes the addition of a hydroxyl group to the meta position of tyrosine, thus forming 3,4-dihydroxy-L-phenylalanine (l-DOPA). 

An ECD measures the current generated by electroactive analytes in the HPLC eluent between electrodes in the flow cell. It offers sensitive detection (pg levels) of catecholamines, neurotransmitters, sugars, glycoproteins, and compounds containing phenolic, hydroxyl, amino, diazo, or nitro functional groups. The detector can be the amperometric, pulsed-amperometric, or coulometric type, with the electrodes made from vitreous or glassy carbon, silver, gold, or platinum, operated in the oxidative or reductive mode. Manufacturers include BSA, ESA, and Shimadzu. 

The catecholamines produce their action by direct combination with receptors located on the cell membrane. In 1948, Ahlquist divided the adrenergic receptors into two main groups - alpha and beta. The alpha receptor stimulation produces excitatory effect and beta receptor stimulation usually produces inhibitory effect. 

Another group of transmitters involved in the control of the cardiovascular system by the autonomous nervous system includes the catecholamines, adrenaline and noradrenaline. In acinar submandibular gland cells of the rat the administration of 10 4 mol/1 adrenaline elicits a reduction in dye coupling from 97 to 75.3% dye-coupled cells [Kanno et al., 1993]. This could not be mimicked with isoprenaline, but was inhibited with phenoxybenzamine. Thus, the uncoupling effect of adrenaline in this preparation is mediated by stimulation of the a-adre-noceptor, whereas a stimulation of the P-adrenoceptor has no effect. 

All of the effects of the catecholamines bound to (3 adrenergic receptors and of glucagon, ACTH, and many other hormones appear to be mediated by adenylate cyclase. This integral membrane protein catalyzes the formation of cAMP from ATP (Eq. 11-8, step a). The reaction, whose mechanism is considered in Chapter 12, also produces inorganic pyrophosphate. The released cAMP acts as the second messenger and diffuses rapidly throughout the cell to activate the cAMP-dependent protein kinases and thereby to stimulate phosphorylation of a selected group of proteins (Fig. 11-4). Subsequent relaxation to a low level of cytosolic cAMP is accomplished by hydrolysis of the cAMP by a phosphodiesterase (Eq. 11-8, step fr).166/167 jn thg absence of phosphodiesterase cAMP is extremely stable kinetically. However, it is thermodynamically unstable with respect to hydrolysis. 

Tillet Y, Batailler M, Krieger-Poullet M, Thibault J (1990) Presence of dopamine-immunoreactive cell bodies in the catecholamine group A15 of the sheep brain. Histochemistry 95 327-333. 

Out of more than 150 different reactions catalyzed by the methyltransferases more than 90 are carried on small molecules. The methyl groups serve here as important chemical building blocks required for the construction of essential cellular components and metabolites. A-methylation of the smallest amino acid glycine is responsible for regulating AdoMet/AdoHcy ratio in the eukaryotic cells (5). Catechol O-methyltransferase (COMT) is responsible for dopamine and other catecholamine... 

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