Adrenergic modulation of small bowel haemodynamics in interdigestive motility state of man

Objective We previously reported a new application of semi-invasive laser-D oppler flowmetry (LDF) to record small intestinal haemodynamics in man unde r basal motor conditions, i.e. during phase I of the migrating motor comple x (MMC), In the present study, we evaluated the complete MMC cycle and its haemodynamics in humans; specifically, adrenergic influence on blood flow i n all three: MMC phases was studied. Design Twenty-one fasting healthy male volunteers (21-44 years) were studie d during two complete MMC cycles: the first as control period, the second a s experimental period with different adrenergic drugs or saline. Methods Recording of LDF of intestinal blood flow was performed by attachin g two single-fibre microprobes to a small intestinal manometry tube, which simultaneously monitored luminal pressure changes. Results Clonidine and oxymetazoline, two alpha(2)-adrenoceptor agonists, si gnificantly decreased blood flow during all phases of the MMC cycle, In con trast, the non-selective beta-adrenoceptor agonist isoprenaline induced pha se 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 bowe r haemodynamics are in operation throughout phases I, II and III of MMC. Ou r findings support the use of the semi-invasive LDF technique to measure dr ug-induced haemodynamic changes in the fasting gut. Eur J Gastroenterol Hep atol 11:257-265 (C) 1999 Lippincott Williams & Wilkins.