Figure 6
The inhibitory effect of tramadol on peristalsis remained unaffected by 5-HT receptor antagonists (5-HT Antagon). The increase in PPT due to the submaximally effective concentrations of 30 μM (-)-tramadol, (+)-tramadol and O-desmethyltramadol was not reduced by pre-treatment with the combination of the 5-HT receptor antagonists methysergide (1 μM) plus tropisetron (1 μM). The bars represent means with SEM, n = 6 – 8 segments. There was no significant difference relative to the values measured after vehicle (Tyrode's solution) administration.