Deafferentation-Induced Redistribution of MMP-2, but Not of MMP-9, Depends on the Emergence of GAP-43 Positive Axons in the Adult Rat Cochlear Nucleus

Figure 1

Time course and distribution of MMP-9 and MMP-2 realignments in AVCN on the side of cochlear ablation (CA), shown in 40 μm thick sections stained with DAB and flat embedded in epon. (a) In AVCN of control animals, numerous neurons were strongly immunoreactive for MMP-9 in their cytoplasm (arrows). (b and c) By POD1 and POD3, MMP-9 immunoreactivity decreased in the cytoplasm of most neuronal somata. Beaded collars of MMP-9 immunoreactive particles emerged close to the plasma membrane (arrowheads). (d) By POD7, the pattern of MMP-9 staining has almost returned to control level (a). (e) MMP-2 was strongly expressed in the cytoplasm of AVCN neurons in control animals. The white line indicated around the cytoplasm of one neuron shows the sample field for quantitative analysis of MMP-staining intensity in neuronal cytoplasm used to obtain the data shown in Figures 6 and 7(e). (f) By POD1, only marginal changes in MMP-2 staining were seen. A derangement seen in tissue texture is caused by disintegrating auditory nerve fibers. (g) By POD3, the content of MMP-2 in cytoplasm of AVCN neurons slightly decreased. (h) This decrease continued towards POD7 when beaded collars of MMP-2 positive particles became visible in direct vicinity to the cell's plasma membrane (arrowheads). (i) and (h) Neutralization of the primary antibody prior to the staining procedure (i) and omission of the primary antibody against MMP-9 (j) verified specificity of the immunostaining. (k) Omitting incubation with antibody raised against MMP-2 resulted in failure of staining. Global contrast adjustment was identical for all photographs in this figure. Scale bar: 20 μm.