Electron microscopic and pharmacologic evidence for a functional adrenergic innervation of the smooth musculature in the human fallopian tube.

ABSTRACT

Triple fixation for electron microscopy of the isthmic region of the human Fallopian tube distinguished adrenergic nerve terminals through their content of synaptic vesicles with a diameter of 50-60 nm. Non-vascular adrenergic nerves were found both outside and within smooth muscle bundles. Adrenergic varicosities, partly devoid of their Schwann cell ensheathing, frequently approached the smooth muscle cells within a distance of about 200 nm, and sometimes as close as 60-100 nm. These close contacts often occupied a considerable area of the naked varicosity. Electrical field stimulation of adrenergic nerves in the isthmic smooth muscle preparations in vitro induced an alpha-receptor mediated, frequency-dependent contractile response. The results show that the sympathetic nerves in the human Fallopian tube are able to exert a motor control of its smooth musculature, and may thus be involved in local functions essential for the normal fertilization process.