Developmental changes in serotonin and 5-hydroxyindoleacetic acid concentrations and opiate receptor binding in rat spinal cord following neonatal 5,7-dihydroxytryptamine treatment.

Normal levels of serotonin and 5-hydroxyindoleacetic (5-HIAA) were measured in the developing rat spinal cord and brain stem using HPLC. Serotonin, 5-HIAA and 3H-naloxone binding were monitored following neonatal 5,7-dihydroxytryptamine (5,7-DHT) treatment. Serotonin in the spinal cord develops biphasically with peaks at gestation day 21 (E21) and postnatal day 8 (P8) while 5-HIAA peaks at P3 and between P8 and P11. In the brain stem, serotonin gradually rises from E15 to adult levels which are reached by P32 while 5-HIAA rises sharply to P15 and thereafter decreases to adult levels by P32. 5,7-DHT treatment neonatally causes greater than 50% reduction of serotonin and 5-HIAA in the spinal cord through P32. Opiate receptor binding in the spinal cord is reduced acutely by about 22% and remains slightly depressed into adulthood.