Figure 6. Population density and sex effects on plasma corticosterone and oxytocin in Paigen diet-fed HypoE mice.

HypoE mice were housed in mixed genotype groups (HypoE and one or more SRBI^+/−ApoeR61^h/h littermates per group, 4–5/cage, gray bars) or singly (1/cage, black bars). Beginning at two months of age the animals were switched from a normal chow diet to the Paigen diet. After 19 days of Paigen diet feeding, the mice were weighed, plasma and hearts were harvested, heart weights measured and plasma levels of corticosterone and oxytocin were determined. The values presented are from the HypoE mice only; they do not include the companion (group housing) SR-BI^+/−ApoeR61^h/h mice. A Plasma corticosterone levels: group housed males, n = 11; singly housed males, n = 14; group housed females, n = 16; singly housed females, n = 12. B Plasma oxytocin levels: group housed males, n = 8; singly housed males, n = 8; group housed females, n = 12; singly housed females, n = 11. Data are means ± SD. Statistically significant differences were determined by unpaired t-test. C Correlation of oxytocin levels and heart-to-body weight ratios for all HypoE mice (n = 39). Gray and black circles indicate group and single housing, respectively. Statistics were evaluated using Spearman’s rank correlation.