Adrenergic responses of the various smooth muscle layers at the human uterotubal junction

The different muscle layers at the human uterotubal junction (UTJ) were mechanically separated, and 1-mm wide muscle strips were isolated and mounted in organ chambers for isometric recording of contractile activity. It was found that the adrenergic neurotransmitter noradrenalin elicited an inhibition of the spontaneous phasic activity in the inner longitudinal and the intermediate circular layers but caused a clear-cut excitatory response in the outer, spiral-shaped (uterine) layer. The excitatory response was totally blocked by treatment with phenoxybenzamine, an alpha-adrenoceptor antagonist, whereas the inhibitory effects were abolished after pretreatment with the beta-adrenoceptor antagonist propranolol. The data demonstrate a differentiated distribution of alpha- and beta-adrenoceptors in the smooth musculature at the proximal end of the tubal isthmus. It is suggested that this arrangement might serve an important purpose in the physiologic control of ovum transport in women.