Effects of spinal cord injury on the rat estrous cycle.

Approximately 3000 women of childbearing age are afflicted with spinal cord injuries each year and many experience temporary amenorrhea immediately following injury. In the present study, the effect of mid-thoracic spinal contusions on the rat estrous cycle was examined. The sixteen rats used for this study all had 4-day cycles (proestrus, estrus, metestrus, diestrus), as determined during the 2 weeks prior to injury. Following contusion at the T8 spinal level (made using the Infinite Horizon impactor device), seven of the animals (44%) experienced a temporary interruption in the progression of the estrous cycle (mean of 9.4 days delay), which was not correlated with impact force or total damage at the lesion epicenter. The presence of a delay was, however, correlated with damage/sparing of ventromedial white matter at the lesion epicenter. The results indicate that the rat's hormonal status is an experimental variable that is present during the acute phase following spinal cord injury. The temporary nature of the cycle delay may reflect compensatory mechanisms related to the dual innervation (spinal and vagal nerve supply) of the ovaries.