Concentration-dependent stimulation of intestinal phase III of migrating motor complex by circulating serotonin in humans.
1. The influence of circulating 5-hydroxytryptamine (serotonin) on small intestinal motility was investigated in healthy volunteers. 2. Small intestinal motility was studied by means of a constantly perfused multi-channel manometry tube, connected to a computer system. 3. Intravenous infusions of either 5-hydroxytryptamine at increasing doses or saline were given over a period of 4 h. 4. 5-Hydroxytryptamine infusion dose-dependently increased plasma 5-hydroxytryptamine from approximately 2 to 10 and 25 nmol/l respectively, as well as urinary excretions of 5-hydroxytryptamine and 5-hydroxyindole acetic acid, a major 5-hydroxytryptamine metabolite. 5. The number of phase III of the migrating motor complex originating in the small intestine was dose-dependently increased by 5-hydroxytryptamine, and found to correlate to the plasma concentration of 5-hydroxytryptamine. The fraction of phase III also increased at the expense of phase II activity. In addition, 5-hydroxytryptamine increased the motility index, propagation velocity of phase III activity and the amplitude of contractions during phase III. 6. Whereas the low dose of 5-hydroxytryptamine (15 nmol.min-1.kg-1) had no haemodynamic effects, an increase in heart rate by approximately 20 beats/min, without change in blood pressure, was observed at the higher dose (60 nmol.min-1.kg-1). Respiratory parameters did not change during infusion of 5-hydroxytrytamine at either dose. 7. In conclusion, elevation of circulating 5-hydroxytryptamine by intravenous infusion results in more frequent and faster propagating migrating motor complexes in the human small intestine during the inter-digestive period.
Lördal
M
M
Department of Gastroenterology and Hepatology, Karolinska Hospital, Stockholm, Sweden.
Wallén
H
H
Hjemdahl
P
P
Beck
O
O
Hellström
P M
PM
D000328:Adult; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000652:urine; D007421:Intestine, Small; D008297:Male; D008365:Manometry; D016065:Myoelectric Complex, Migrating / Q000187:drug effects*; D012701:Serotonin / Q000097:blood / Q000494:pharmacology* / Q000652:urine; D018709:Statistics, Nonparametric
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid