Figure 4. Interrupted stress has greater impact even when number of stress exposures is constant.

A) It is possible that the diminished habituation after the interruption is due to a smaller total number of stress exposures. To test this, the interrupted stress pattern with 7 exposures (bottom) was compared to a daily stress pattern with 7 exposures (top). Solid bars represent stress exposure, open bars represent no stress, and oval represents the test day. B) There was significantly greater number of pellets over the course of 7 daily restraint episodes compared to their control (left) and a greater number of pellets one the final day of restraint in the 7 day interrupted pattern compared to the 7 daily pattern (right). C) The body weight at the end of the course of 7 daily pattern was not significantly different between the control andd stress group. D) The body weight of the 7 daily stress group was not significantly different than the interrupted stress group after the final episode. However, there was a significant interaction between body weight and treatment over the course of stress exposures, consistent with a difference in the pattern of weight gain. E) Adrenal gland weight (normalized to body weight) was significantly greater in the interrupted stress group compared to the equi-numbered daily restraint group. * indicates p<0.05 in post hoc comparisons after Bonferroni corrections (B, left; E). # indicates significant Pattern x Day interaction in a two-way ANOVA.