Impulse velocity and conduction pathways in rat myometrium

¹ Civil Aeromedical Research Institute, Federal Aviation Agency, Oklahoma City, Oklahoma

Velocity of conduction of impulses in rat myometrium is graded with dosage of estradiol cyclopentyl propionate. A single dose of the hormone was given and allowed to act for various periods of time before the animals were killed. Uteri from castrate control animals did not conduct impulses. The earliest effect of the hormone was seen 2 hr after injection, at which time an impulse was conducted with a velocity of 1.25 cm/sec. Velocity increased until 72 hr postinjection when it was 4.65 cm/sec. Uteri from rats 9 weeks postinjcction still conducted impulses at 3.51 cm/sec. Impulses travel on pathways that may be functionally discrete, though one pathway can excite another. Impulses also travel at different velocities on different pathways and it appears that there are bundles of longitudinal muscle fibers directly opposite the mesometrium that conduct faster than adjacent bundles. Pathways must sometimes be facilitated in order for impulses to travel the full length of the uterine horn.

Key Words: smooth muscle • uterus • hormones estrogen • action potentials • impulse transmission • conduction velocity

Submitted on January 13, 1964