Effects of parachlorophenylalanine on indoleamines in maturing mouse brain.

Abstract 1. 1. The effects of parachlorophenylalanine (PCPA), the tryptophan-5-hydroxylase (T5-H) inhibitor, on the maturation of 5-hydroxytryptamine (5-HT) and 5-hydroxy-indole acetic acid (5-HIAA) have been studied in regions of the maturing mouse brain. 2. 2. PCPA does not affect 5-HT levels in 1-day old mice treated on the day of birth, but does decrease it at all subsequent stages studied after 24 hr exposure. 3. 3. 5-HIAA level was unchanged in 1-day old and adult mice treated 24 hr earlier but was lower in almost all brain regions at other stages studied. 4. 4. The results lend support to the hypothesis that the newborn brain is able to synthesize more indoleamine than previously suspected but is unable to store it during the stages of neuronal outgrowth and terminalization.