Developmental effects of intraperitoneal saline injections in neonatal rats

The response to neonatal intraperitonal (IP) saline injections was investigated in neonatal male and female rats from split- and whole-litters. The results demonstrate that male or female rats housed under split-litter conditions and subjected to daily IP injections during the early neonatal period have the same body weight and plasma corticosteroid and testosterone (males only) levels as littermate controls. On the other hand, treated male and female animals from whole-litters weigh significantly less than controls. Additionally, plasma testosterone and cortisteroids from treated males did not differ from controls at any age tested, but treated females from whole-litters had significantly elevated corticoids at days 100 and 150 when compared to controls. These results suggest that when doing developmental studies involving IP injections, it would be advisable to house animals under split-litter conditions.