Dopamine, monitoring

Yoshitake T, Yoshitake S, Fujino K, Nohta H, Yamaguchi M, Kehr J. High-sensitive liquid chromatographic method for determination of neuronal release of serotonin, noradrenaline and dopamine monitored by microdialysis in the rat prefrontal cortex. J Neurosci Meth 2004 140 163-8. 

Elderly patients prescribed one of the dopamine receptor agonists are monitored closely for which of the following adverse reactions ... 

FIGURE 4-23 Experimental setup for monitoring dopamine release by exocytosis, from a cell body. The microelectrode and glass capillary (containing the chemical stimulant) are micromanipulated up to the cell body. (Reproduced with permission from reference 82.)... 

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. 

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... 

For patients receiving dopamine agonists, the maximal suppression of GH and IGF-I levels may take up to 3 months to achieve. Once stable control of biochemical markers is achieved with dopamine agonists or somatostatin analogs, monitor GH and IGF-I levels annually.6... 

In patients with macroprolactinomas, monitor visual field at baseline and repeat the test 1 month after initiation of a dopamine agonist. 

Metoclopramide is the drug of choice for enhancement of lactation when improved feeding technique fails to increase milk flow48 (Table 44-5). Metoclopramide exerts its effect through dopamine antagonism. Increases in milk production should be noted within 2 to 5 days of metoclopramide initiation. Monitor patients for extrapyrimidal symptoms. 

Normal saline or dopamine at renal perfusion dose of 2 mcg/kg per minute for oliguria monitor for electrolyte abnormalities and replace as indicated. 

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.

O Neill R. D., Fillenz M. (1985). Simultaneous monitoring of dopamine release in rat frontal cortex, nucleus accumbens and striatum effect of drugs, circadian changes and correlations with motor activity. Neuroscience 16(1), 49-55. 

F. Gonon, M.F. Suaud-Chagny, and M. Buda, Fast in vivo monitoring of electrically evoked dopamine release by differential pulse amperometry with untreated carbon fibre electrodes, in Proceedings of Satellite Symposium on Neuroscience and Technology (A. Dittmar and J.C. Froment, eds), p. 215. Lyon... 

The extent of receptor supersensitivity after unilateral nigrostriatal lesions can be quantified by measuring the extent of rotational behavior. After selective nigrostriatal lesions have been produced in rats by injections of 6-hydroxydopamine into the substantia nigra, the number of dopamine receptors in the ipsilateral corpus striatum increases markedly, and the increase in the number of receptors may correlate with the extent of behavioral supersensitivity as monitored by rotational behavior [52]. Thus, the increase in receptor density appears to play a role in the behavioral supersensitivity of these animals. 

Hurd YL, Kehr J, Ungerstedt U. 1988. In vivo microdialysis as a technique to monitor drug transport correlation of extracellular cocaine levels and dopamine overflow in the rat brain. J Neurochem 51(4) 1314-1316. 

Sharp T, Ljimgberg T, Zetterstrom T, Ungerstedt U. 1986. Intracerebral dialysis coupled to a novel activity box—a method to monitor dopamine release during behaviour. Pharmacol Biochem Behav 24(6) 1755-1759. 

Fig. 7.6 Nonbound SCH 23390 in a competitive MS binding assay for dopamine Di receptors monitored at a transition from 288.1 91.2 m/z from binding samples without or with (+)-butaclamol. Intensity (/) is shown (a) without (+)-butaclamol, (b) with 30 nM (+)-butaclamol, (c) with 10 pM (+)-butaclamol. (a-c) Representative chromatograms after HPLC separation (RP8 column solvent CH3CN/0.1% HCOOH in H2O 1 1 300 pL min ).

Hypotension Hypotension (postural) occurs regularly in about 50% of patients while they are supine, manifested by dizziness, light-headedness, vertigo, or faintness. Tolerance occurs unpredictably but may be present after several days. Hypotension with supine systolic pressure above 75 mm Hg need not be treated unless symptomatic. If supine systolic pressure falls below 75 mm Hg, infuse dopamine or norepinephrine to increase blood pressure use dilute solution and monitor blood pressure closely because pressor effects are enhanced by bretylium. Perform volume expansion with blood or plasma and correct dehydration where appropriate. Transient hypertension and increased frequency of arrhythmias Transient hypertension and increased frequency of arrhythmias may occur due to initial release of norepinephrine from adrenergic postganglionic nerve terminals. 

Dopamine receptor binding Buspirone can bind to central dopamine receptors. Monitoring Patients have been treated for several months without ill effect. If used for extended periods, periodically reassess the usefulness of the drug. 

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