HOW THE BRAIN PROTECTS ITSELF FROM STRESS
AND RELATED DISORDERS
The
degree of control that an animal has over a stressor is a potent modulator of
the stressor’s impact on central nervous system (CNS) and the whole organism.
It is known that uncontrollable stressors produce a number of outcomes that do
not occur if stress is controllable. Trevor W. Robbins in Nature Neuroscience (Controlling stress: how the brain protects itself from depression. Nature
Neurosci. 8, 261-262, 2005) presents
a new study in rats indicating that descending inputs from the prefrontal
cortex to the serotoninergic midbrain system signal the controllability of
stress.
Recent
research on controllability has focused on brainstem nuclei such as the dorsal
raphe nucleus (DRN). J. Amat et al. (Medial prefrontal cortex determines how stressor controllability affects
behaviour and dorsal raphe nucleus. Nature Neurosci. 8, 365-371,
2005) found that infra-limbic and pre-limbic regions of
the ventral medial prefrontal cortex (mPFCv) in rats detect whether a stressor
is under the organism’s control. When a stressor is controllable, stress
induced activation of the DRN is inhibited by the mPFCv, and the behavioural
consequences of uncontrollable stress are blocked.
This
suggests a new function for the mPFCv, and implies that the presence of control
inhibits stress-induced neural activity in brainstem nuclei, in contrast to the
prevalent view that such activity is induced by a lack of control.