Dopamine determination

An imprinted poly[tetra(o-aminophenyl)porphyrin] film, deposited on a carbon fibre microelectrode by electropolymerization, was used for selective determination of dopamine [208] in the potential range of —0.15 to 1.0 V. This chemosensor has been used successfully for dopamine determination in brain tissue samples. The dopamine linear concentration range extended from 10 6 to 10-4 M with LOD of 0.3 pM. However, this LOD value is very high compared to that of the dopamine voltammetric detection using polyaminophenol MIPs prepared by electropolymerization [209]. Dopamine was determined by CV and DPV at concentrations ranging from 2 x 10 s to 0.25 x 10 6 M with LOD of 1.98 nM. This LOD value is lower than that of PM dopamine detection [133]. 

The former crmsists of a significant enhancement of sensor selectivity when Nafion is added as the outermost layer of an electrode coating the electrocatalytic properties of many electrode coatings that are the object of different chapters of this monograph are combined with the selectivity conferred by this ion-exchange polymer. In this respect, a most frequently reported applicatiOTi is addressed to lower the ascorbic acid interference in amperometric sensors for glucose or for dopamine determination. 

Virag L, Whittington RA. Highly sensitive chromatographic assay for dopamine determination during in vivo cerebral microdialysis in the rat. J Chromatogr B Anal Tech Biomed Life Sci 2002 772 267-72. 

J.P. Li, J. Zhao and X.R Wei, A sensitive and selective sensor for dopamine determination based on a molecularly imprinted electropolymer of o-aminophenol. Sens. Actuat B-Chem 140 (2) 663-669, 2009. 

Analysis of single mammalian ceUs by capiUary electrophoresis has been reported usiag on-column derivatizatioa and laser-iaduced fluoresceace detectioa (11). Dopamine and five amino acids were determined ia iadividual rat pheochromocytoma ceUs after on-column derivatizatioa. 

MAINTAINING ADEQUATE TISSUE PERFUSION. When a patient is in shock and experiencing ineffective tissue perfusion tiiere is a decrease in oxygen resulting in an inability of die body to nourish its cells at die capillary level. If die patient has marked hypotension die administration of a vasopressor (a drug diat raises die blood pressure because of its ability to constrict blood vessels) is required. The primary health care provider determines die cause of die hypotension and then selects the best mediod of treatment. Some hypotensive episodes require die use of a less potent vasopressor, such as metaraminol, whereas at other times a more potent vasopressor, such as dobutamine (Dobutrex), dopamine (Intropin), or norepinephrine (Levoplied) is necessary. 

The less potent vasopressors, such as metaraminol, also require close patient supervision during administration. The nurse follows the same procedure as that for norepinephrine and dopamine but may take blood pressure and pulse determinations at less frequent intervals, usually every 15 to 30 minutes. The nurse needs sound clinical judgment to detemrine the frequency because there is no absolute minimum or maximum time limit between detenninations. 

Mr. Cole is receiving dopamine for the treatment of severe hypotension. In planning the care for Mr. Cole, determine what would be the most important aspects of nursing management. Explain your answers. 

It is appropriate at this juncture to illustrate the power of chemiluminescence in an analytical assay by comparing the limits of sensitivity of the fluorescence-based and the chemllumlnescence-based detection for analytes in a biological matrix. The quantitation of norepinephrine and dopamine in urine samples will serve as an illustrative example. Dopamine, norepinephrine, and 3,4-dihydroxybenzy-lamine (an internal standard) were derivatized with NDA/CN, and chemiluminescence was used to monitor the chromatography and determine a calibration curve (Figure 15). The limits of detection were determined to be less than 1 fmol injected. A typical chromatogram is shown in Figure 16. 

Escribano, J. et al., Characterization of monophenolase activity of table beet polyphenol oxidase determination of kinetic parameters on the tyramine/dopamine pair, J. Agric. Food Ghem., 45, 4209, 1997. 

Because LCEC had its initial impact in neurochemical analysis, it is not, surprising that many of the early enzyme-linked electrochemical methods are of neurologically important enzymes. Many of the enzymes involved in catecholamine metabolism have been determined by electrochemical means. Phenylalanine hydroxylase activity has been determined by el trochemicaUy monitoring the conversion of tetrahydro-biopterin to dihydrobiopterin Another monooxygenase, tyrosine hydroxylase, has been determined by detecting the DOPA produced by the enzymatic reaction Formation of DOPA has also been monitored electrochemically to determine the activity of L-aromatic amino acid decarboxylase Other enzymes involved in catecholamine metabolism which have been determined electrochemically include dopamine-p-hydroxylase phenylethanolamine-N-methyltransferase and catechol-O-methyltransferase . Electrochemical detection of DOPA has also been used to determine the activity of y-glutamyltranspeptidase The cytochrome P-450 enzyme system has been studied by observing the conversion of benzene to phenol and subsequently to hydroquinone and catechol... 

Biochemical analyses of 6-OHDA-injected animals revealed a 93 percent depletion of dopamine. The tissue was assayed using electrochemical detection following separation by high-pressure liquid chromatography (Felice et al. 1978). recorded as ng/mg protein in the nucleus accumbens and compared to control rats with sham lesions (sham=65.5 4.4, lesion=4.9 1.5 t(39)=23.4). A lesion was defined as complete if 75 percent or more of the dopamine was determined to be depleted from the nucleus accumbens compared to mean sham group values. 

Figure 7.2 Diurnal variation of extracellular dopamine in the non-human primate putamen. Dopamine concentrations (dm) as determined by high-pressure liquid chromatography of microdialysates obtained from the putamen of two rhesus monkeys across their 12 12 h lights-on (waking 7 00 am 7 00 pm) and lights off (sleep 7 00 pm-7 00 am) periods. Ten minute samples (2 pl/min sampling rate) were derived from nine individual 8 h sessions in each animal in which the sleep-wake state was monitored simultaneously by standard electrophysiological parameters.

Weiss, F., Lorang, M.T., Bloom, F.E., and Koob, G.F., Oral alcohol self-administration stimulates dopamine release in the nucleus accumbens genetic and motivational determinants, J. Pharmacol. Exp. Ther., 267, 250, 1993. 

Damsma, G., Westernik, B.H., de Vries, J.B., and Horn, A.S., The effect of systemically applied cholinergic drugs on the striatal release of dopamine and its metabolites, as determined by automated microdialysis in conscious rats, Neurosci. Lett., 89, 349, 1988. 

Villemagne, V., Yuan, J., Wong, D.F. et al. Brain dopamine neurotoxicity in baboons treated with doses of methamphetamine comparable to those recreationally abused by humans evidence from [llC]WIN-35,428 positron emission tomography studies and direct in vitro determinations. J. Neu-rosci. 18 419, 1998. 

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