Fig. 7.

Numbers of synapses (B,C, F) and dense bodies (D, E, G) were evaluated in electron micrographs taken from five sections through the SG, with a distance of 250 μm, within an area of 0.74 × 0.74 mm per section (A) from one NT-4-deficient mouse and one wild-type littermate. Criteria for synapses were presynaptic and postsynaptic membrane specializations and accumulations of synaptic vesicles in the active zone (B,C). Although ultrastructural features of synaptic nerve endings were not overtly changed in NT-4 knock-outs compared with wild-type animals (B, C), there were significant quantitative differences in numbers of synapses (F). Numbers of lysosomes in neuronal cell bodies and dendrites seemed to be augmented in the NT-4 knock-outs, however, without becoming significant (G). Scale bars: B, C, 1 μm; D,E, 2 μm.