3,4-Dihydroxyphenylacetic acid (DOPAC) as an index of noradrenaline turnover: Effects of hydergine® and vincamine

Summary Among the drugs commonly used in the treatment of memory disorders of the elderly, vincamine and hydergine^® have been shown to moderately increase the firing rate of noradrenergic locus coeruleus (LC) neurons. Since changes in electrical activity of noradrenergic neurons are generally reflected in corresponding alterations of the turnover of this transmitter, the effects of these drugs on the accumulation of 3,4-dihyroxyphenylacetic acid (DOPAC) and dopamine (DA) in the presence and absence of the dopamine-?-hydroxylase inhibitor, FLA 63, were studied in the LC as well as in two of its projection areas, the hippocampus and the cerebellum. Characterization of this procedure with the a₂-adrenoceptor antagonist, idazoxan, the corresponding agonist, clonidine, the a₁-adrenoceptor antagonist prazosine, and haloperidol, suggested that- DOPAC changes are more suitable than those of DA or DOPAC/DA ratios in reflecting changes in noradrenaline (NA) turnover,- inhibiting DBH is advantageous if NA turnover is to be measured in projection areas, but not in LC, and- haloperidol and prazosine, in principle, did not affect NA turnover.