Characterization of monoaminergic terminals in the neostriatum of neonatal rats: an electron microscopic morphometric...

Monoaminergic (MA) boutons in the neostriatum of neonatal rats were studied by using 5-hydroxydopamine. We found: (a) bouton size averaged 0.6 micron in diameter; (b) terminal density was 68 boutons per 7200 micron2 area; (c) synaptic frequency was 33.2%; and (d) MA neurons constituted 9.2% of all boutons. This population was much lower than that reported in immature neocortex where MA neurons are a major innervation.