Abstract
In WGA-HRP tracing study of goldfish optic nerve, the majority of regenerating axons arrived at the tectum 3-5 weeks after optic nerve transection. On the other hand, it is unknown when the centrifugal fibers from nervus terminalis reinnervate to the retina after axotomy. To investigate the recovery of these efferent fibers, we used goldfish and zebrafish visual system by immunohistochemical and WGA-HRP tracing studies. The efferent fibers express FMRF amide (Phe-Met-Arg-Phe-NH2 ) that is a molluscan cardioexcitatory peptide, and gonadotropin-releasing hormone (GnRH). In the control retina, FMRF amide and GnRH immunoreactivity were colocalized in the inner nuclear and the nerve fiber layer. In the optic nerve, their positive staining could be sparsely seen a dotted-like appearance. After optic nerve transection, the immunoreactivity of FMRF amide and GnRH in the retina disappeared by 20-30 days, while their expression gradually recovered 40-50 days after axotomy. This regeneration process of efferent fibers was roughly correlated with the regeneration time of afferent fibers of optic nerve. We also studied the efferent fibers of optic nerve in various animal species. [Jpn J Physiol 55 Suppl:S171 (2005)]
