SIMPLE PROCEDURE FOR THE ASSAY OF BRAIN BIOGENIC-AMINES BY SELECTED-ION MONITORING - ITS APPLICATION TO THE ELUCIDATION OF THE MECHANISM OF PROLACTIN-RELEASE INDUCED BY 3-IODO-L-TYROSINE

A simple method for the assay of brain biogenic amines by selected-ion monitoring was applied to examination of the effects of 3-iodo-L-tyrosine on the hypothalamic-median eminence concentrations of dopamine, noradrenaline and serotonin in the rat. Thirty minutes after its administration iodotyrosine (50 mg/kg) caused a highly significant (P > 0·0005) rise in serum prolactin and a highly significant (P > 0·0025) fall in the concentration of dopamine in the hypothalamus and median eminence where the levels reached 50% of control levels. Less marked but significant falls were also observed in the hypothalmic (P > 0·05) and median eminence (P > 0·0025) concentrations of noradrenaline after iodotyrosine administration. Serotonin concentration was significantly reduced (P > 0·025) in the median eminence but not in the hypothalamus after iodotyrosine administration. These findings suggest that iodotyrosine exerts its prolactin stimulating effect by blockage of dopamine synthesis rather than by receptor blockade. © 1979 ASEG.