1984 Volume 83 Issue 2 Pages 115-122
In the preceding study, neonatal deaths were observed when an analgesic, butorphanol tartrate (BT), was administered subcutaneously to female rats during the perinatal and lactating periods. In the present study, cross-fostering using CRJ:CD (Sprague-Dawley) rats was employed to clarify the cause of death. When the litters naturally delivered from dams receiving BT (25 mg/kg/day, s.c.) during the perinatal period were switched among one another within the BT-treated dams or placed with control (saline-treated) dams, the viability of newborns on postpartum day 3 was significantly lowered. Since some of the BT-treated dams were observed to neglect the delivery cares that were fundamental to dams such as removing amnions, umbilical cords and placentas, as well as gathering and lactating to newborns immediately after natural delivery, it was considered that death after cross-fostering was the result of the pups being emaciated before cross-fostering. This finding was supported by the fact that a significant elevation in the viability was revealed when the newborns Cesarean-delivered from BT-treated dams were placed with control or untreated dams. No significant effects of BT were observed on the viability and body weight of newborns at birth and on those of pups from postpartum day 3 through the weaning day.
