Recovery of spinal cord volume in postnatal rats following prenatal exposure to morphine.

A previous study has shown that the spinal volume of 18-day fetal rats is decreased by 20% after maternal administration of morphine on gestation days 12-18. In the present study, the volume of the first thoracic spinal cord segment was measured in offspring of morphine or saline-injected and pairfed dams on days 6, 15 and 80 postnatally. The following volumes were measured within the segment: hemisegment, gray matter, white matter, dorsal horn, ventral horn and length. On the sixth day postnatally, the hemisegment, gray matter and dorsal horns are significantly reduced in morphine-treated and pairfed offspring. By the fifteenth day postnatally, only the gray/white ratio is reduced while the length of the segment is significantly increased in morphine-treated fetuses. The spinal measurements in pairfed offspring are normal by 15 days postnatally. These results indicate that the effect of morphine on developing spinal cord may be partially due to undernutrition; however, morphine causes a more pronounced and longer-lasting effect than undernutrition alone.