PRENATAL DEVELOPMENT OF THE SEROTONIN TRANSPORTER IN MOUSE-BRAIN

The prenatal development of the serotonin transporter was analyzed in mouse brain and spinal cord by autoradiographic localization of [H-3]c italopram binding. Transporter expression started at embryonic day (E) 12 in two discontinuous bands in the anterior and posterior brainstem . Labeling extended cranially and caudally, reaching the basal diencep halon at E 13, the septal complex at E 15, and the cerebral cortex at E 16. The caudal extension of the labeling descended at the ventrolate ral margin of the spinal cord and reached lumbar levels at E 14. At E 17-E 18, [H-3]citalopram binding emerged in the striatum, amygdaloid a rea, ventrobasal thalamus, paraventricular and periventricular hypotha lamic nuclei, and substantia nigra. The overall spatiotemporal express ion pattern of the serotonin transporter in the mouse agrees with data on the immunohistochemical localization of serotonin in the rat embry o. These results suggest that serotonergic fibers have the equipment t o engage in transmitter reuptake long before synapse formation, and th at transporter expression might represent a prerequesite for the devel opmental functions exerted by serotonin.