Wildtype (WT), substance P deficient (SP KO, Tac1-/-
), and CGRP receptor deficient (RAMP1 KO, RAMP1-/-
) mice underwent behavioral testing and then distal tibia fracture (FX) with hindlimb casting for 3 weeks, then the cast was removed and behavioral testing repeated (n = 10-12). Baselines did not differ between WT, SP KO, and RAMP1 KO mice. Controls included WT mice with no treatment (WT Control), WT mice with crush injury (no FX) of the distal ankle (WT Crush), and WT mice with hindlimb casting (no FX) for 3 weeks (WT Cast). WT Crush mice failed to develop nociceptive or vascular changes, but WT Cast mice developed hindpaw von Frey allodynia and unweighting, but no warmth or edema (A-D). The absence of SP signaling (SP KO FX) partially inhibited post-FX allodynia (A) and unweighting (B) and completely blocked warmth (C) and edema (D), compared to the WT FX mice. Similarly, the loss of CGRP signal (RAMP1 KO FX) partially inhibited post-FX allodynia (E) and unweighting (F), completely blocked hindpaw warmth (G), and had no effect on hindpaw edema (H), compared to WT fracture mice. For detailed descriptions of the hindpaw behavioral assays see Methods. A negative von Frey threshold value (A, E) represents mechanical allodynia on the fracture side. A value less than 100% for weight bearing represents unweighting (B, F). Positive values for temperature (C,G) or thickness (D,H) represent warmth or edema. * P < 0.05, **P < 0.01, and ***P < 0.001 vs WT Control, #P < 0.05, and ##P < 0.01 vs WT FX.