SIMILAR PROPERTIES OF FETAL AND ADULT AMINE TRANSPORTERS IN THE RAT-BRAIN

A variety of drug classes, including psychomotor stimulants and antide pressants, interact with monoamine transporters in order to exert thei r effects. Although these transporters have been extensively character ized in the adult brain, little is known about uptake mechanisms in th e fetal system. High affinity dopamine (DA) and serotonin (5-HT) uptak e in the striatum and frontal cortex, respectively, were examined in r at fetuses (embryonic day 20; E-2O). These results were then compared to uptake in adult rat synaptosomal preparations of the same regions. The data indicate that the fetal (E-20) uptake mechanism is sodium-dep endent. Furthermore, the potency of various agents to inhibit transpor ter function was assessed. These drugs produced a concentration-depend ent inhibition of uptake, and the resulting IC50 values were not signi ficantly different from those obtained in the adult preparations. Our results provide evidence that the affinity of monoamine uptake inhibit ors for fetal (E-20) DA and 5-HT transporters is similar to that obser ved with adult transporters. This observation has broad implications w hen considering neuronal development and in utero exposure to drugs th at exert their effects through these transporters.