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The contents of dopamine, noradrenaline and their deaminated metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylethylene glycol (DOPEG) were determined in rats in two noradrenaline cell body regions, i.e., the superior cervical ganglion and the locus coeruleus, and in one dopamine cell body region, the substantia nigra. In the two noradrenaline cell body regions, the tyrosine hydroxylase inhibitor alpha-methyltyrosine rapidly lowered the contents of noradrenaline and DOPEG and it lowered the contents of dopamine and DOPAC even more rapidly. The dopamine-beta-hydroxylase inhibitor FLA-63 swiftly elevated the content of dopamine and it lowered the content of noradrenaline in the two noradrenaline regions, but it was ineffective in the substantia nigra. The monoamine oxidase inhibitor pargyline rapidly reduced the deaminated catechols and increased somewhat the contents of the two amines in the superior cervical ganglion and in the locus coeruleus. The alpha-methyltyrosine-induced disappearance of dopamine in the two noradrenaline cell body regions was markedly inhibited by FLA-63 and pargyline in combination, but not by only one of the two drugs. The results indicate that most of the dopamine in the superior cervical ganglion and in the locus coeruleus occurs in the cell body region of noradrenaline neurons, whereas only a minor part of the dopamine in the superior cervical ganglion is present in SIF cells. Axonal transport did not contribute to the disappearance of dopamine in the superior cervical ganglion. A high dose of reserpine reduced the contents of dopamine and noradrenaline in the superior cervical ganglion and in the locus coeruleus, indicating that most of the amines is present in storage granules.(ABSTRACT TRUNCATED AT 250 WORDS)

The deaminated monoamine metabolites 3-methoxy-4-hydroxyphenylethyleneglycol (MOPEG), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were determined electrochemically following organic solvent extraction and reverse-phase, high performance, liquid chromatography in four regions of the mouse brain. In the noradrenaline (NA)-predominant regions (hemispheres, brain stem), the ratio of the concentrations of DOPAC plus HVA to NA plus dopamine (DA) was approximately the same as in the DA-predominant regions (corpus striatum, limbic system). Yohimbine and reserpine elevated the concentrations of DOPAC and HVA both in the NA- and the DA-predominant regions. The effect of yohimbine was somewhat enhanced by the alpha 1-receptor blocking agent prazosin in the NA-predominant regions. The concentration of MOPEG was increased by yohimbine and decreased by reserpine. The concentrations of DOPAC and HVA were lowered by clonidine, but not by apomorphine in the NA-predominant regions of reserpine-treated mice. In the DA-predominant regions, apomorphine, but not clonidine, reduced the concentrations of DOPAC and HVA. The effects of clonidine and apomorphine were reversed by yohimbine and haloperidol, respectively. The results indicate that the concentrations of the acid DA metabolites DOPAC and HVA in the NA-predominant regions reflect the rate of synthesis of DA in the NA neurons.