抄録
The optic nerve contains a small number of efferent fibers. The efferent fibers, terminal nerve originating from the olfactory bulb, travel along with the optic nerve and terminate in the inner plexiform layer of the retina. After optic nerve transection, the majority of afferent regenerating axons reinnervated the tectum 3-5 weeks by WGA-HRP tracing study. However, it has not been reported when the efferent fibers regenerate after axotomy. In this study, we investigated the recovery time of the efferent fibers in goldfish and zebrafish visual system after optic nerve transection. The efferent fibers were identified by their immunoreactivity to gonadotropin-releasing hormone (GnRH) and FMRFamide (Phe-Met-Arg-Phe-NH2 ). In control fish retina, localization of GnRH and FMRFamide signals was observed in the nerve fiber layer, and in the border of the inner nuclear and inner plexform layer. These signals of GnRH and FMRFamide were lost by optic nerve lesion. Furthermore, the expression of mRNA of GnRH receptor also disappeared from retina by 10 days after axotomy. The mRNA expression of GnRH receptor was recovered 20 days after lesion in the retina, whereas the expression of GnRH and FMRFamide was recovered 80-90 days after axotomy. This regeneration of efferent fibers was longer than that of afferent fibers in optic nerve. [J Physiol Sci. 2007;57 Suppl:S141]
