Chemical UL-induced changes of TNFα-Ir cells in the MVN and IVN. (A) Illustration of the typical labeling in a representative sham rat and in an experimental animal subjected to chemical UL (arsanilate transtympanic injection) observed 8 h after the lesion. Note that chemical UL induces an increased number of TNFα-Ir cells. Scare bar: 100 μm. (B) Quantitative analysis of the effects of chemical UL on TNFα-Ir cells in the MVN and IVN. Data are mean values (± SEM) of the number of TNFα-Ir recorded in the sham rats (black histograms) and in the UL rats (grey histograms) observed at 4, 8 h, 1, 3, 7, and 15 days after the lesion. The data from both sides were pooled for sham and experimental animals. According to Bonferroni's principle, P < 0.01 was considered significant. * P < 0.01, ** P < 0.001, *** P < 0.0001 versus sham values (MVN: medial vestibular nucleus; IVN: inferior vestibular nucleus).