RESUMO
Objective In the present study, we observed the distribution of nitric oxide synthase positive neurons in the developing rat telencephalon and to realize the possible roles of NO in brain development further. Methods NADPH-d histochemical method was used to investigate the micromorphology and distribution of NOS positive neurons in rat telencephalon from embryonic day 14 (El4) to postnatal day 14 (P14). Results At El4, no neurons stained. Labeling was observed in the ventrolateral of the striatum at E15. At E17, positive neurons were seen in the cerebral cortex and piriform cortex. They were cells with small cell bodies, shorter dendrites and less ramification. The stained neurons were either increased or maintained in both number of neurons and intensity during development. At E20, positive cells were found in many regions. Many positive neurons were present in the piriform cortex, ventrolateral of the striatum and bed nucleus of the stria terminalis. They acquired larger size and more complex dendrites. After birth, intensely stained NOS positive fibers were distributed widely in the cerebral cortex and striatum. Stained cells were found in the corpus callosum and hippocampus also. The distribution pattern of positive cells at P14 was essentially similar to that reported in adult rats. Conclusion The distinctive temporal and spatial expression pattern of nitric oxide synthase positive neurons in the telencephalon indicated that NO may play an important role in brain development and maturation.