Study Finds Evidence Linking The Brain's Cognitive Control Regions With Stress Contr...( extent that the animal no longeris abl...)

Based upon earlier studies, the researchers suspected that three main areas were responsible for stress responses:

• The paraventricular nucleus. The PVN is the central core of the body's stress response and is primarily responsible for secretion of stress hormones called glucocorticoids. These chemicals regulate the metabolism of carbohydrates, proteins and fats in the body. It responds to chemical signals sent from other areas.

• The hypothalamus. It is responsible for the body's homeostasis, or balance. It in large part dictates the overall health of the animal through control of food and water intake, cardiovascular tone, body temperature and hormone release.

• The hippocampus. It is the cognitive area of control. It's where learned stresses, like 'bear in cave' are processed. UK scientists believe that signals sent from this area first have to pass through the hypothalamus before reaching the PVN.

Researchers used snippets of antisense RNA to locate an enzyme called glutamic acid decarboxylase (GAD) in the brain. GAD speeds production of an inhibitory chemical transmitter called gamma-aminobutyric acid (GABA).

Two forms of the GAD enzyme exist: GAD65, the stored form and GAD67, the rapidly released form. Each form responded differently based upon the duration of stress (acute or chronic) applied to rats; these regulators were active only in sections of the brain that the researchers suspected to be control areas.

In the first experiment, rats were placed under short-term restraint to provoke acute stress reactions. There was a significant amount of stress-generated expression of GAD67 in the hippocampus and hypothalamus. The induction was rapid and transient, suggesting an immediate need to manufacture GABA in the acute stress situation.

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Contact: Kim Cumbie
krcumb0@pop.uky.edu
(606) 323-6363
University of Kentucky Medical Center
19-Aug-1998