Fig. 5. LY2828360 does not alter impact of morphine on colonic motility following acute or chronic morphine dosing.

(A) The schematic shows the timing of experimental procedures. Mice received once daily injections (i.p.) of morphine for 12 days. The black vertical arrows show the days when the colonic motility assay was performed, and the grey vertical arrows show the days when the hot plate assay (Fig. 6) was performed. (B) Acute high dose morphine (10 mg/kg i.p. x 1 day) produced longer bead expulsion times compared to all other doses, consistent with opioid-induced slowing of colonic motility and was not affected by LY2828360 treatment. (C) Chronic high dose morphine (10 mg/kg i.p. x 12 days) increased glass bead expulsion times, consistent with absence of tolerance, and was not affected by LY2828360 treatment. (D) High dose morphine (10 mg/kg i.p.) slowed glass bead expulsion time irrespective of injection day. Low dose morphine (1 mg/kg i.p. x 12 days) produced longer bead expulsion times compared to acute treatment on day 1. A modest, but reliable attenuation of bead expulsion time was observed following chronic high dose morphine (10 mg/kg i.p. x 12 days) compared to acute treatment on day 1. (E) High dose morphine (10 mg/kg i.p.) prolonged glass bead expulsion time irrespective of injection day and the presence or absence of LY2828360 treatment. (F) Acute high (10 mg/kg i.p. x 1 day) and middle dose (3 mg/kg i.p. x 1 day) morphine reduced fecal boli accumulation compared to the low dose (1 mg/kg i.p. x 1 day), consistent with the development of morphine-induced constipation and was not affected by LY2828360 treatment. (G) Chronic high dose morphine (10 mg/kg i.p. x 12 days) reduced fecal boli accumulation compared to vehicle , consistent with the development of morphine-induced constipation and was not affected by LY2828360 treatment. (H) Fecal boli accumulation on day 1 and day 12 of morphine alone treatment showed a main effect of the dose but no reliable post hoc differences between groups for the differing morphine doses. (I) Fecal boli accumulation on day 1 and day 12 of morphine + LY2828360 treatment did not differ based upon dose of morphine or injection day. Data are expressed as mean ± S.E.M. (n = 6 per group) **** P < 0.0001 vs. all other groups, *** P < 0.001 vs. all other groups, # # P < 0.01 vs. low dose morphine group, # P < 0.05 vs. low dose morphine group, + P < 0.05 vs. vehicle group, two-way ANOVA followed by Bonferroni's post hoc test. ****P < 0.05 vs. all other groups,**P < 0.01 vs. all other groups, XX P < 0.01 vs. acute treatment, X P < 0.05 vs. acute treatment, two-way repeated measures ANOVA followed by Bonferroni’s post hoc test.