Cranial nerves and brain fiber systems of the medaka fry as observed by a whole-mount staining method.

The cranial nerves and the brain fiber systems of the medaka (Oryzias latipes) fry are revealed by a whole-mount staining method. Newly hatched fry of an albino strain of the medaka were fixed, partially digested with trypsin, treated in 1% Triton X-100, and finally immunohistochemically stained using anti-neurofilament protein (70K+160K+210K) antibodies. Since both head skin and eyes were colorless in the albino fish, the three-dimensional distribution of of nerve fibers in the brain could be readily observed in whole specimens without interference of pigment cells. All cranial nerves and main fiber systems in the adult fish were differentiated in the fry brain. Using this method, the distribution of nerves to the ocular muscles and the periorbital pit organs was shown.