Antihypertensive effects of L-tryptophan are not mediated by brain serotonin

L-Tryptophan produces a significant antihypertensive effect in spontaneously hypertensive rats while D-tryptophan does not change blood pressure. Both isomers of tryptophan significantly increase brain serotonin to the same extent at a time when the antihypertensive effect of L-tryptophan is maximal. Thus, the antihypertensive effects of L-tryptophan do not appear to be mediated by brain serotonin.