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Adrenergic modulation of small bowel haemodynamics in interdigestive motility state of man
M Thollander1, B Gazelius, P M Hellström
1Department of Medicine, Karolinska Hospital, Stockholm, Sweden.
Objective:
We previously reported a new application of semi-invasive laser-Doppler flowmetry (LDF) to record small intestinal haemodynamics in man under basal motor conditions, i.e. during phase I of the migrating motor complex (MMC). In the present study, we evaluated the complete MMC cycle and its haemodynamics in humans; specifically, adrenergic influence on blood flow in all three MMC phases was studied.
Design:
Twenty-one fasting healthy male volunteers (21-44 years) were studied during two complete MMC cycles: the first as control period, the second as experimental period with different adrenergic drugs or saline.
Methods:
Recording of LDF of intestinal blood flow was performed by attaching two single-fibre microprobes to a small intestinal manometry tube, which simultaneously monitored luminal pressure changes.
Results:
Clonidine and oxymetazoline, two alpha2-adrenoceptor agonists, significantly decreased blood flow during all phases of the MMC cycle. In contrast, the non-selective beta-adrenoceptor agonist isoprenaline induced phase II-like activity with a significant increase in blood flow. Propranolol, a beta-adrenoceptor antagonist, did not alter motility but decreased blood flow throughout the MMC cycle.
Conclusions:
Both alpha- and beta-adrenergic mechanisms modifying small bowel haemodynamics are in operation throughout phases I, II and III of MMC. Our findings support the use of the semi-invasive LDF technique to measure drug-induced haemodynamic changes in the fasting gut.