Figure 4. Long teeth, normal sensorimotor coordination and impaired nocifensive behaviors in CKO mice. A, Malocclusion in a P28 CKO mouse (arrows) compared with a control (Ctrl). B, P28 CKO mice exhibiting normal sensorimotor coordination. C, Rotarod assay. No significant difference was found between Ctrl and CKO mice on time (seconds) staying on accelerating rotarod. Ctrl, n = 10, 45.6 ± 5.5 s; CKO, n = 10, 39.4 ± 5.2 s. p = 0.44. D, von Frey test. CKO mice showed a higher withdrawal threshold than Ctrl mice. Ctrl, n = 7, 0.29 ± 0.04 g; CKO, n = 7, 1.36 ± 0.05 g. ***p < 0.001. E, F, Hot plate assay. CKO mice showed longer latency (seconds) in response to both 50°C and 54°C stimuli compared with Ctrl mice. E, For 50°C: Ctrl, n = 8, 23.4 ± 1.2 s; CKO, n = 8, 56.5 ± 1.0 s. ***p < 0.001. F, For 54°C: Ctrl, n = 6, 7.6 ± 1.0 s; CKO, n = 6, 26.8 ± 1.3 s. **p < 0.01. G, Capsaicin hindpaw injection assay: measuring the duration (seconds) of licking and flinching. Abolished response in CKO mice. Ctrl, n = 9, 31.8 ± 3.2 s; CKO, n = 9, 0.0 ± 0.0 s. H, p-ERK immunostaining on P28 lumbar spinal transverse sections after heat stimulation. Arrows indicate superficial laminae. I, Quantitative analysis of p-ERK+ neurons per set of sections through L3–L6. Ctrl, n = 4, 190 ± 44; CKO, n = 4, 31 ± 9. *p < 0.05. Error bars indicate SEM.