OPRM1 and colitis: MOR agonist DAMGO administered twice daily at the dose of 0.02 mg/kg BW (i.p.)and FFAR4 antagonist AH 7614 administered twice daily at the dose of 1 mg/kg BW (i.p.)did not attenuate DSS-induced colitis alone or in co-administration, as indicated by inflammatory indicators (Figure 2a–d).