AJP - Regulatory, Integrative and Comparative Physiology, Vol 249, Issue 4 410-R416, Copyright © 1985 by American Physiological Society
Direction of uterine contractions during estrus in ewes: a reevaluation
P. L. Toutain, P. G. Marnet, M. P. Laurentie, R. Garcia-Villar and Y. Ruckebusch
In four ewes direction of propagation of uterine contractions was evaluated
using an electromyographic technique during 15 entire estrous periods;
120,101 propagations were analyzed. When horns were considered separately
89.9% of all propagations were classified into three main modes: ascending
(34.3%), descending (59.85%), and divergent (5.85%). When both horns were
analyzed simultaneously, horn's synchronicity was observed in most
instances; on this basis, eight modes of propagation were identified of
which three accounted for two-thirds of all propagation: synchronous
descending (24.9%), reciprocal propagation (descending on one horn and then
ascending on contralateral horn) (22.1%), and isolated descending
propagation (18.0%). A time-dependent pattern of propagation throughout
estrus was clearly identified, the percentage of ascending propagations
reaching a minimum (16.5%) and the percentage of descending propagation
reaching a maximum (77%) at peak uterine motility level. By considering
both direction of uterine propagation and cervical mechanical activity, a
new hypothesis concerning two aspects of sperm transport (speed and
mechanism) was formulated. It is hypothesized that the high prevalence of
descending propagations is important to reduce sperm cell population by
selecting the most vigorous spermatozoa; such selection is possible when
the mechanical cervical activity is low or absent (cervix open); when
cervical mechanical activity is high (cervix closed), it is suggested that
both descending and ascending propagations participate in sperm transport
by back and forth motion of luminal fluid within the uterine lumen.
