Expression of maternal behavior and activation of the bed nucleus of the stria terminalis during predatory threat exposure: modulatory effects of transport stress.

Past work has established that levels of maternal care provided to rat pups during the postpartum period plays an important role in shaping development of the stress response system, such that high levels of pup licking and grooming and active nursing behaviors are associated with more efficient hypothalamic-pituitary-adrenal responses to stressors in adulthood. Furthermore, a prior study from our laboratory has demonstrated facilitation of maternal care for five days following a one-hour predator odor exposure on the day of giving birth. The present study was an investigation of the effects on maternal care during a one-hour predator odor exposure administered on the day of giving birth, with or without the addition of transport stress immediately prior to the odor exposure.

Stress responses of adolescent male and female rats exposed repeatedly to cat odor stimuli, and long-term enhancement of adult defensive behaviors.

In order to characterize the short- and long-term effects of repeated stressor exposure during adolescence, and to compare the effects of using two sources of cat odor as stressor stimuli, male and female adolescent rats (postnatal day (PND) ∼ 38-46) were exposed on five occasions to either a control stimulus, a cloth stimulus containing cat hair/dander, or a section of cat collar previously worn by a cat. Relative to control stimulus exposure, activity was suppressed and defensive behavior enhanced during exposure to either cat odor stimulus (most pervasively in rats exposed to the collar). Only cloth-exposed rats showed elevated levels of corticosterone (CORT), and only after repeated stressor exposure, but interestingly, rats exposed to the collar stimulus during adolescence continued to show increased behavioral indices of anxiety in adulthood.

Enhanced stress responses in adolescent versus adult rats exposed to cues of predation threat, and peer interaction as a predictor of adult defensiveness.

Development of the hypothalamic-pituitary-adrenal (HPA) axis is influenced by external factors during early life in mammals, which optimizes adult function for predicted conditions. We have hypothesized that adolescence represents a sensitive period for the development of some aspects of adult stress response regulation. This was based on prior work showing that repeated exposure of rats to a stressor across an adolescent period increases fearfulness in a novel environment in adulthood and results in lower levels of dopamine receptor subtype-2 protein in prefrontal cortex.

Investigation of sex differences in behavioural, endocrine, and neural measures following repeated psychological stressor exposure.

Animal models of repeated stressor exposure have generally been limited to physical stressors, despite the fact that the purpose of such models is to represent repeated stress in humans, which is usually psychological in nature. The present study was undertaken to investigate the behavioural, endocrine, and neural responses to a repeated psychological stressor exposure in male and female rats. Long-Evans rats were exposed to cat odour or a control condition for 1 h each day from Day 1 to Day 22.

Periadolescent stress exposure exerts long-term effects on adult stress responding and expression of prefrontal dopamine receptors in male and female rats.

Recent research has demonstrated that experiential/environmental factors in early life can program the adult stress response in rats, and this is manifest as altered hypothalamic-pituitary-adrenocortical activity and behavior in response to a stressor. Very little work has been devoted to investigating whether the environment during adolescence plays a similar role in modulating ongoing developmental processes and how this might affect adult stress responding. Periadolescent predator odor (PPO) exposure was used here as a naturalistic model of repeated psychological stress.