Dextro-phenylalanine inhibits potassium-evoked 3H-noradrenaline release from hypothalamus but not of 3H-dopamine from rat caudate nucleus.

Action of dextro-phenylalanine (d-Phe) on catecholamine release elicited by K+20 mM has been studied in isolated slices of rat central nervous system (CNS). d-Phe (3 x 10(-3)M) produced inhibition of the fractional release of 3H-noradrenaline but not of 3H-dopamine. The mentioned effect is Ca2+ dependent and was antagonized when this ion was incremented to 2.6 mM in the medium or in the presence of ionophore A-23187 (4 x 10(-5)M). Neither acetylsalicylic acid nor indomethacin (prostaglandin biosynthesis inhibitors) interferes with the effect of d-Phe, showing that by itself it would not reach through the prostaglandin pathway. d-Phe modified neither the noradrenaline neuronal uptake nor its metabolism at the CNS. The findings suggest that d-Phe acts through a Ca2+-dependent mechanism, possibly by specific receptors and in parallel with feedback circuits that involve alpha-adrenoceptors, muscarinic receptors, or prostaglandins.