Figure 3.

Postsurgical incision model shows low levels of behavioural modulation. Incision- (red traces/columns), vehicle- (black traces/columns), incision/codeine 7 mg/kg (green traces/columns), and incision/codeine 30 mg/kg—treated (blue traces/columns) rats were tested on two baseline- and two time points post injection for their responses to mechanical- and heat stimuli. Incision surgery was performed at time point 0, as indicated by the grey dashed line (A,B). Codeine treatment groups received two bolus injections on the last testing day (evening/morning; 7 mg/kg each). At this time point, all groups were subjected to the testing sequence (C–K). (A) von Frey test/mechanical paw withdrawal thresholds. (B) Plantar heat test/radiant-heat induced paw-withdrawal latency. (C–F) Automated classification of voluntary behaviours in the spectroscopy apparatus. The parameters are ordered in general behaviours (C), tracklength (D), overall activity (E), and velocity (F). (G) 3 chamber apparatus/time spent in a compartment with an unknown animal. (H) Elevated plus maze/time spent in open arm exploration. (I) Splash-test/time in induced grooming behaviour. (J) Saccharine preference. (K) Nest building scoring (median ± 95% confidence interval, Kruskal-Wallis test with Dunn's multiple comparison test). Data are expressed as mean ± SEM and analysed using a RM two-way ANOVA (A,B), followed by Bonferroni's correction. For single time point behavioural tests, a one-way ANOVA with Bonferroni's correction was used (C–K, n = 10 for the control group, n = 9 for the incision model, n = 8 for the incision/codeine 7 mg/kg—and the incision/codeine 30 mg/kg groups). * indicates a significant difference to the vehicle control (p < 0.05); § indicates a significant difference to the incision-group (p < 0.05). For detailed p-values of group comparisons, see Table 1.