Modification of the Direction of Uterine Contractions by Intra-Uterine Devices in the Ewe

Abstract

The direction of uterine contractions in vivo was studied in oestrous ewes by recording the motility of exteriorized uteri on cine film. In eight control ewes, 58% of 1156 contractions moved towards the oviduct, while 16% moved towards the cervix. In eight ewes with a plastic spiral in the lumen of one horn, only 17% of 927 contractions moved towards the oviduct; 70% of the contractions moved towards the cervix. The effect of the IUD on the direction of uterine contractions may explain inhibition of sperm transport and ovum fertilization iǹ IUD' ewes.A plastic spiral placed in one uterine horn of the ewe inhibits sperm transport and ovum fertilization (Hawk, 1967). Inhibition of sperm transport is probably not due to suppression of uterine motility because the in vitro motility of strips of myometrium taken from ewes with a spiral in one uterine horn was greater than that of strips taken from control ewes (Brinsfield & Hawk, 1968). Also, attempts to overcome the antifertility effect of the spiral with various compounds which stimulate uterine contractions were unsuccessful (Warren & Hawk, 1968). The possibility remained that a spiral might inhibit sperm trans¬ port by altering some qualitative aspect of uterine motility. The present experiment was conducted to determine whether the presence of a spiral in one uterine horn would alter the direction of uterine contractions in vivo.Sixteen mature, parous ewes were checked twice daily for oestrus by the use of aproned rams. Ewes were laparotomized on Day 10 or 11 of an oestrous cycle (Day of oestrus = Day 0), a small puncture was made in the wall of one uterine horn near its anterior end and a plastic spiral measuring 32 mm in length and 10 mm in diameter was screwed in a posterior direction into the lumen through the puncture so that the spiral lay in the lengthwise centre of the horn. In eight ewes, the spiral was anchored in place by one suture through the uterine wall. The spiral was removed immediately from the remaining eight ewes; these animals served as sham-operated controls. Ewes were assigned to each group at random and the horn to be operated upon within each ewe was also selected at random.At the first oestrus of each ewe that occurred more than 2 weeks after insertion of the spiral, the ewe was anaesthetized with sodium pentobarbital and the uterus was carefully exteriorized through a mid-ventral incision. 535

Uterine Contractions in the Ewe During Progestagen-Regulated Oestrus

“…The proportions of total contractions moving towards the oviducts, not moving clearly in either direction, or moving towards the cervix were 54%, 33% and 13%, respectively. These figures are similar to those taken previously from cine-film recordings of uterine contractions in other control ewes (6-9 contractions/min and directional movements of 58%, 26% and 16%, respec¬ tively; Brinsfield & Hawk, 1969 (Quinlivan & Robinson, 1967, 1969Hawk & Conley, 1971, 1972.…”

“…The effect of progestagen on the direction of uterine contractions in the ewe is somewhat similar to the effect of placing a plastic spiral in the uterine lumen, which 'reverses' the direction of uterine contractions and inhibits sperm transport (Hawk, 1967;Brinsfield & Hawk, 1969). Whether the effects of a plastic spiral and progestagen treatment have similar physiological bases is not clear, but it appears that uterine motility patterns in oestrous ewes can be disrupted by seemingly diverse treatments.…”

Spontaneous motility of the cervix in cyclic and ovariectomized ewes and changes induced by exogenous hormones

“…In addition, the independence of uterine and cervical motility in vivo has been demonstrated in ruminants (Chen, MacDonald & Hawes, 1966;Fitzpatrick, 1957; Stys, Clewell & Meschia, 1978). Stress conditions or general anaesthesia impair the passage of spermatozoa in the ewe (Brinsfield & Hawk, 1969).…”

The Uterus of the Ewe I. Secretion From the Cannulated Uterus

“…In the ewe, as in other species, the presence of an intra-uterine foreign body interferes with the physiological function of the organ and causes infertility. Intra-uterine foreign bodies in the ewe have been shown to interfere with the development of the corpus luteum (Ginther, Pope, and Casida, 1965;Stormshak, Lehmann, and Hawk 1967), to modify uterine motility (Brinsfield and Hawk 1969), to inhibit sperm transport and promote spermicidal conditions (Hawk 1967), and in certain circumstances to modify cycle length (Moore and Nalbandov 1953;Nalbandov, Moore, and Norton 1955;Inskeep et al 1962). Therefore, there would seem good reason to suggest that in the cannulated uterus, the volume of fluid collected may be influenced by local effects of the cannula on the uterus.…”