Mice of various ages between birth and adulthood were injected daily for 5 days with the serotonin specific uptake inhibitor citalopram (LU 10-171). 2 days later they were reinjected with citalopram 2. 2 hr, 1 day and 3 days following the last injection animals were killed and their brains assayed for 5-hydroxytryptamine (5-HT) and 5-hydroxyindole acetic acid (5-HIAA). 3. Brains were found to still respond to citalopram's acute action despite the fact younger brains had undergone long term alteration of 5-HIAA stores. 4. The possibility that indoleamines are subject to different regulatory mechanisms in young brain is discussed.
