Developmental Changes in Serotonin and 5-HydroxyindoIeacetic Acid Concentrations and Opiate Receptor Binding in Rat Spinal Cord Following Neonatal 5,7-Dihydroxytryptamine Treatment

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Abstract
Normal levels of serotonin [5-hydroxytryptamine, 5-HT] and 5-hydroxyIAA (5-HIAA) were measured in the developing rat spinal cord and brainstem using HPLC [high performance liquid chromatography], 5-HIAA and 3H-naloxone binding were monitored following neonatal 5,7-dihydroxytryptamine (5,7-DHT) treatment. 5-HT 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 at P8-P11. In the brainstem, 5-HT 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 > 50% reduction of 5-HT and 5-HIAA in the spinal cord through P32. Opiate receptor binding in the spinal cord is reduced acutely by .apprx. 22% and remains slightly depressed into adulthood.