Effect of 1 µM melatonin (MT) on the outflow of 5-HT (A) and 5-HIAA (B) from the muscle layer-free mucosal preparations in the absence (MT alone) or presence (+MT) of 1 µM βAla-NKA-(4-10). βAla-NKA-(4-10) was present from 120 to 140 min of incubation, as indicated by the horizontal bar. Melatonin was present from 120 to 160 min of incubation, as indicated by the horizontal dotted line. Ordinates: outflow of 5-HT (A) and 5-HIAA (B), expressed as per cent of the mean outflow of first two collections (100–120 min). Each point represents the means ± SEM from 6 to 10 experiments. *P < 0.05, **P < 0.01, Significance of difference from the paired control. 5-HT, 5-hydroxytryptamine; 5-HIAA, 5-hydroxyindoleacetic acid; βAla-NKA-(4-10), [β-Ala8]-neurokinin A4-10.