Figure 2.

Results of the hotplate and tail withdrawal assays in the morphine study. A. Averaging over all drug (including saline) and time conditions in the hotplate test, males had a higher %Maximum Possible Effect (%MPE) than females (*p=0.009). B. The graphs shows %MPE averaged across time. In the hotplate test, morphine at 10mg/kg had significant analgesic effect (*p=0.000001) relative to the 0–1 mg/kg morphine group. The response to morphine tended to be higher in males than females irrespective of their sex chromosome complement (p=0.06 sex by drug interaction; +, p=0.02 comparison of males vs. females at 10mg/kg). C. Graphs show results averaged across all drug doses, including saline, so that the main effects of sex and sex chromosome complement can be seen. In the tail-withdrawal test, the %MPE over time differed as a function of both sex and sex chromosome complement because XX males had a more variable response than the other three groups (sex by sex chromosome by time interaction, p=0.035). D and E. In the tail withdrawal test, there was a statistically significant interaction of time, sex chromosome, sex, and drug (p=0.015), meaning that the effects of sex chromosome, sex, and drug were different at different times. To illustrate those differences, the %MPE are graphed separately for T=15 and T=45 minutes. At T=15 minutes after morphine injection, there was a differential effect of morphine on XX vs. XY females (+, p=0.07 in XY females and not significant for XX females) but not between XX and XY males (* both p<0.05). At 45 minutes after injection (T=45), the effect of morphine was significant only in XY males (**p =0.0002).