Aggravation of bone degradation and proteoglycan depletion in murine collagen-induced arthritis in α7 subunit of nicotinic acetylcholine receptor (α7nAChR)- defi cient (α7nAChR-/-) mice compared with wild-type (WT) mice (n=20 per group). (A) Representative radiographs of the knee joints of an α7nAChR-/- mouse and a WT mouse. p1720.