retinal ganglion cell axon extension is unaffected by 5-HT receptor activation during visual system development.

Activating 5-HT receptors with the agonist Zolmitriptan was previously shown to facilitate retinal ganglion cell (RGC) axon extension from ectopic eye primordia transplanted to the ventral fin. To determine if 5-HT receptor activation influenced entopic RGC axonal outgrowth toward the optic tectum during typical visual system development, we reared embryos in 50 μΜ Zolmitriptan then visualized optic tracts with anterograde HRP labeling. Zolmitriptan did not significantly alter entopic RGC extension in the contralateral brain. Consequently, RGC axon extension in ectopic but not entopic locations is influenced by altering serotonergic signaling .