Myogenic and neurogenic control of electrical and mechanical activity in human oviductal smooth muscle

Abstract

Isolated strips from isthmic and ampullary muscle layers of the human fallopian tube were investigated with the sucrose-gap technique and in organ baths. Generally good correlation existed between electrical and mechanical activity, but dissociation was also noted. The isthmic external longitudinal layer (IEL) was characterized by slow waves of depolarization and broad 'spikes'. Tonic contraction followed depolarization, and phasic waves followed the spikes. In the other layers, regular spikes and phasic contractions dominated. Late in the menstrual cycle, more irregular patterns and slow waves, which could synchronize spike activity, were found. Automaticity tended to be highest in the late proliferative phase. Active response to stretch was best demonstrated in IEL. Excitatory alpha-adrenergic responses (hypopolarization, firing and contraction) to noradrenaline and nerve stimulation dominated in the IEL. In the other layers, beta-adrenergic inhibition prevailed. Non-adrenergic, non-cholinergic neurogenic inhibition was demonstrated. Decrease in spike frequency and hyperpolarization seemed to be as prominent as during beta-adrenergic inhibition. Muscarinic stimulation by acetylcholine was recorded as depolarization, spikes and contraction. However, a role for cholinergic nerves could not be defined. Thus, the human oviductal smooth muscle belongs to the single unit category; its activity can be modified during the menstrual cycle, by stretch and by excitatory and inhibitory nerves.