A new method of measuring catecholamine (CA) sulfate permitted us to detect its presence in rat brain for the first time. The procedure consisted of separating the CA sulfate from the free CA by alumina adsorption followed by passage through Dowex, and measuring the CA sulfate by a radioenzymatic assay in the presence of a sulfatase. This method permitted demonstration of the presence of dopamine sulfate, and occasionally, of norepinephrine and epinephrine sulfate in the hypothalamus, striatum, and hippocampus of rat brain.

The effects of subcutaneous injection of L-beta-3,4-dihydroxyphenylalamine (L-DOPA) on the concentrations of the catecholamines and catecholamine sulfates in the central and peripheral nervous systems of the rat were studied. The results showed that free 3,4-dihydroxyphenylethylamine (DA, dopamine) increased rapidly and markedly in the hypothalamus and striatum after L-DOPA but DA sulfate did not change. Increased concentrations of DA sulfate were detected in the CSF and in the plasma, where it reached a concentration of 130.8 +/- 12.8 ng/ml at 2 h, seven times the level of free DA (19.1 +/- 2.9 ng/ml). In the kidney the ratio of DA sulfate to free DA was reversed in favor of free DA. Urine samples of L-DOPA-treated rats showed a higher increase of free DA than DA sulfate, but free norepinephrine (NE) and NE sulfate remained unchanged. Concentrations of free DA and free NE in the adrenal glands of L-DOPA-treated rats showed no change. Adrenal DA sulfate and NE sulfate were not detectable in the control and L-DOPA-treated rats, suggesting that the adrenal glands lack the capacity to take up or store catecholamines and their sulfate counterparts from the plasma.

The treatment of Sprague-Dawley rats with monoamine oxidase (MAO) inhibitors (pargyline, tranylcypromine) profoundly affects dopamine (DA) and norepinephrine (NE) metabolism in the brain. In these rats injection of L-dopa led to large increases in norepinephrine (NE), normetanephrine (NMN) and 3-methoxytyramine (3-MT) in brain tissues. The response of MAO-inhibited rats to L-dopa contrasted sharply with those not treated with the MAO inhibitor; the latter showed no change in NE, NMN and 3-MT after similar administration of L-dopa. The increase of NE in pargyline-treated rats correlated closely with that of DA in the hypothalamus and in the brain stem. This response was greatly diminished in rats previously treated with the neurotoxin 6-hydroxydopamine, but was restored when the treatment with 6-hydroxydopamine was accompanied by desimipramine. This suggests that noradrenergic neurons were the origin of the NE response. The NMN and 3-MT increases occurring only in the rats treated with a MAO inhibitor were highly correlated. The results suggested that MAO inhibitor may affect entry of DA into catecholaminergic storage where NE synthesis takes place and from where DA is released.

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