Contractile effect of acetylcholine on isolated ampullar segment of Fallopian tubes

The Fallopian tubes are scarcely innervated with cholinergic nerve fibers. Acetylcholine released from these nerves contracts smooth muscles of the tubes. The aim of our study was to investigate the effect of acetylcholine on the Fallopian tubes using selective antagonists in different hormonal settings. We have investigated effects of acetylcholine on isolated ampulla of Fallopian tubes taken from 83 patients during abdominal hysterectomy with adnexectomy. Twenty-eight patients were in follicular, 36 were in luteal phase of menstrual cycle, and 19 patients were in menopause. Selective and non-selective muscarinic and nicotinic receptor blockers were used for investigation of the effects. Acetylcholine (from 1.8 to 658.6 microM/l) produced concentration-dependent tonic contraction of ampulla taken from the patients in follicular phase, luteal phase and menopause. The nicotinic receptor blocker mecamylamine (6.5 microM/l) and local anesthetic lidocaine (230.8 microM/l) did not affect the effect of acetylcholine. While M(1)- and M(2)-selective muscarinic receptor blockers pirenzepine (1.6 microM/l) and methoctramine (0.9 microM/l) did not show specific effect, atropine (0.01 microM/l) and selective M(3)-receptor blocker p-fluoro-hexahydro-sila-difenidol (pFHHSiD, 0.2 microM/l) effectively blocked contractions caused by acetylcholine (maximal pA(2) values 9.74 and 7.54, respectively). The affinity of pFHHSiD for muscarinic receptors was highest in the follicular phase. The results of our study suggest existence of functional M(3) muscarinic receptors in ampulla of Fallopian tubes, located on the smooth muscle cells.