Figure 5.

Efficacy of acute morphine treatment on chronic osteoporosis-related cutaneous and musculoskeletal pain and physical function. The effect of an acute intraperitoneal injection of morphine (10 mg/kg) was measured for several hours in mice, 6 months after ovariectomies or sham surgeries. In ovariectomized (OVX) mice, morphine results in a significant reduction in mechanical hypersensitivity (von Frey assay) that persists for several hours (a) and reduces cold hypersensitivity (acetone test) (b). No effects are evident in the cold plate (c), radiant heat paw withdrawal (d), or grip strength (e) assays. Morphine increases the OVX animals' overall activity in the open field test (f). No effects are seen in the sham-operated mice. Data are expressed as means ± standard error of the mean. ^∗P < 0.05; ^∗∗P < 0.01; ^∗∗∗P < 0.001; ^∗∗∗∗P < 0.0001; OVX group with morphine versus vehicle, ^#P < 0.05; and sham-operated group with morphine versus vehicle, two-way repeated measures analysis of variance (factors = group × time), followed by Tukey's test for multiple comparisons.