In Vivo and in Vitro Efflux of Conjugated Amines into Superfusates from Discrete Areas of the Central Nervous System of Cats and Rats
We have previously found (Tyce et al, 1980) considerable amounts of an acid-hydrolyzable conjugate of dopamine (DA), presumably DA-sulfate, in the cerebrospinal fluid (CSF) of dogs following intravenous administration of L-3,4-dihydroxyphenylalanine (L-DOPA). The amounts of this DA conjugate present in the CSF were decreased when α-methyldopahydrazine, which inhibits decarboxylation of L-DOPA in peripheral tissues, was administered in addition to L-DOPA. Since this treatment could be expected to preferentially increase central stores of DOPA and DA (Melamed et al, 1980), our data suggested that the DA conjugate present in the CSF of dogs had been formed in the periphery, and transported into the brain and CSF. Amine sulfates form internal salts carrying little electrical charge at physiological pH and might therefore penetrate biological membranes more readily than the parent amines which are not easily transported across biological membranes (Jenner & Rose, 1973).
KeywordsDopamine Cysteine Bicarbonate Boiling Catecholamine
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