5; Fig. 5.A and ​and2C,D).2C,D). These solitary processes exhibit a beaded structure as they proceed to the base of the developing sensory cells (Fig. 5B). Figure 5 The α7GFP expression during cochlear innervation. Innervation of the developing cochlear structure is revealed by α7GFP labeling. (A) An E13.5 sagittal section shows a group of efferent processes (arrow) that distribute to solitary fibers … The origin of these efferent fibers was examined in serial sections of the E14.5 hind Inhibitors,research,lifescience,medical brain. These fibers appear to originate from a cell grouping in the basal brain stem

caudal to trigeminal nucleus V that could be distinguished by their transient α7GFP expression (Fig. 5C). These cells occur in clusters (Fig. 5C insert) and their prominently labeled processes can be followed using serial section sets to the cochlear structure where they give rise to the fiber bundles and the point of dissemination Inhibitors,research,lifescience,medical associated with the SG (Fig. 5C and insert). The anatomical location of these cells suggest that these cells are within the forming

olive complex, which is consistent with the reports of pioneering fibers that originate from the developing olive complex and extend Inhibitors,research,lifescience,medical to the developing cochlea (Zuo et al. 1999). These fibers were not detected after E15.5. During the E15.5–16.5 period, there was essentially no labeling of neuronal processes by α7GFP (Fig. 5D–F). Inhibitors,research,lifescience,medical However, ongoing innervation of cochlear sensory cells was identified using peripherin labeling (Fig. 5E; see Simmons et al. 1996; Hafidi 1998;

Huang et al. 2007) or for olivocochlear efferents that were identified by labeling for calcitonin gene-related protein (CGRP; Fig. Inhibitors,research,lifescience,medical 5F, Fritzsch 2003). By E18.5, the SG α7GFP signal was present in afferent processes that extend to the base or near vicinity of the IHCs (Fig. 5G). At birth and thereafter (P0–P12 analyzed), the expression of α7GFP was strongly detected in SG afferent fibers where they terminate very near or at the base of IHC sensory cells (Fig. 5H and I). This basic pattern of α7GFP expression was reinforced during the remaining postnatal period as fibers selleck inhibitor continue to form a dense plexus that appears to surround the base of the IHCs. The other efferent fibers not detected by α7GFP continue to be trimmed and also associate with their final targets (Merchan-Perez and Liberman 1996; Simmons et al. 1996; Hafidi 1998; Huang et al. 2007). The outcome of this remodeling was evident by P12 when the SG1 afferent terminals surrounding the IHC were distinguished by strong α7GFP staining of the terminal clusters (Fig. 5I and inset). This was approximately the same time hearing onset occurs in mice (~P10; Kros et al. 1998).