From: The enantiomers of tramadol and its major metabolite inhibit peristalsis in the guinea pig small intestine via differential mechanisms
Δ PPT (Pa)
Vehicle (Tyrode's solution)
n = 54
0.31 ± 1.9
Naloxone (0.5 μM)
n = 18
-10.4 ± 1.6
Methysergide (1 μM) + tropisetron (1 μM)
13.4 ± 2.5
Yohimbine (1 μM) + prazosin (1 μM)
3.0 ± 2.0