Figure 1.
Development of Nav pan immunoreactivity in NL. A, The course of development of the chicken auditory system. B, Tonotopic regions are based on position within the nucleus; the rostromedial one-third is defined as the high-CF region, the middle one-third as the middle-CF region, and the caudolateral one-third as the low-CF region (Rubel and Parks, 1975; see Materials and Methods). C, Immunosignals of Nav pan at three tonotopic regions of NL. Fibrous clusters were observed as early as E9 and became longer and distinct by E15. After E15, the clusters became shorter, particularly in the high-CF regions. Dot-like immunosignals that correspond to nodes of Ranvier appeared at late embryonic periods. D, Cumulative probability of length of clusters in C. Measurements were made for >30 clusters at each CF region in each animal, and three to four animals were used for each age (see Materials and Methods). The curves shifted positively between E9 and E15 at all the CF regions, whereas the curves shifted negatively afterward to a greater extent in the higher-CF regions.