These rats looked and acted exactly the same in ordinary situations, but even the most moderate stress would cause one type to break down. Under calm conditions, these rats could learn mazes, but give them the tiniest stress, and they would unravel and forget everything. The other rats were unaffected. When we examined their brains, we found that early in the development of the stress-reactive rats, there was over-activity in their adrenaline and noradrenaline systems. This small change led to a great cascade of abnormalities in receptor number, sensitivity, and function across many brain
...more
