All data are presented as the mean (± s.e.m.). The %MPE was calculated using Microsoft Excel (Microsoft Corp., Redmond, WA) and Prism was used to calculate the area under the curve. Comparisons between experimental groups were made for the area under the %MPE versus time curve (extent and duration of morphine antinociception; %MPE area under the curve) and performed using the Student’s t test as implemented in the SigmaStat (Aspire Software International, Ashburn, VA) statistical analysis package.
