Effects of Separation and Separation with Supplemental Stroking in BALB/c Infant Mice

Abstract

The purpose of this pilot study was to investigate selected stress, immune, and growth consequences of maternal separation and separation with supplemental stroking in neonatal BALB/c infant mice and their dams. Three groups of 5 litters each (7 pups per litter) were studied. Control litters were undisturbed. Separated litters experienced 3 h of daily maternal deprivation on postnatal days 6 to 10. Separated/stroked litters were separated also, but for 2 h, which was then followed by 1 h of stroking with a wet paintbrush to simulate maternal tactile stimulation. After the experimental period, all animals were returned to the nest and left undisturbed for 5 additional days. One pup fromeac h litter was sacrificed on postnatal days 6, 8, 10, and 15. Spleens and thymuses were removed, weighed, and homogenized for cell sorting, cytokine analysis, and proliferation studies. Blood was drawn for corticosterone levels and hematocrit. Hematocrits and thymus weights were lower in separated mice, suggesting decreased growth and protein synthesis. Separated/stroked pups had increased splenic proliferation responses to conconavalin A and phytohemagglutinin at day 15. Separated dams’ proliferative response to Con A was lower than control dams at day 15. Day 15 decreases in thymic CD8 cells occurred in pups, with an increased thymic H:S ratio in separated pups. CD90 cells were higher at day 15 in separated/stroked pups as were CD25s at day 10 in spleen and thymus. However, gene expression of cytokines was not measurable in spleen and thymic cells, with the exception of-IFN in separated/stroked animals. Pooled organ homogenates were used in this preliminary work, and further studies are needed to more precisely analyze the stress, immune, and growth effects of these interventions.