Figure 4

Quantitative ultrastructural analyses of the number of synaptic terminals apposed to the surface of motor neurons after axotomy. Representative micrographs of the surface of (A,B) contralateral and (C,D) ipsilateral motor neurons from C3H/HePas wild-type (WT) and C3H/HeJ TLR4 mutant mice. At 1 week after peripheral lesion, WT mice had greater preservation of synaptic terminals from the surface of (A) unlesioned and (B) lesioned motor neurons. (E) Graph of the total synaptic contact in unlesioned and lesioned neurons; there was greater synaptic covering in WT mice compared with TLR4 mutant mice on both unlesioned and lesioned sides. The black arrows indicate the location of motor-neuron membrane surfaces from which synaptic terminals were (C) in contact with or (D) detached from the surface of the motor neuron. The white asterisk indicates a microglial cell close to a synaptic terminal. E) Graph of the total synaptic covering in unlesioned and lesioned neurons; there was greater synaptic covering in WT mice compared with TLR4 mutant mice on both sides. (F) Graph of the total number of synaptic terminals per 100 μm of motor-neuron membrane; note the difference between genotypes on the lesioned side. (G) Graph of the total bouton length on the motor-neuron membrane in lesioned and unlesioned neurons; the difference is presented before axotomy. (H–J) Graphs of F-, S- and C-terminal numbers per 100 μm of motor-neuron membrane, respectively. A greater preservation of F-type terminals was seen before and after axotomy in WT mice, and, a greater preservation of S-type terminals was seen before lesioning in WT mice. * P<0.05 and ** P<0.01. Scale bar: 0.5 μm.