MINERALOCORTICOID AND GLUCOCORTICOID RECEPTOR ANTAGONISTS IN ANIMAL-MODELS OF ANXIETY

The behavioral effects of intracerebroventricular (ICV) administration of a specific mineralocorticoid receptor (MR) antagonist [RU28318 (10 -50 ng/2 mu l)], a glucocorticoid receptor (GR) antagonist [RU38486 (1 -50 ng/2 mu l)], or both antagonists (50 ng/2 mu l), were studied in t wo different animal models of fear and anxiety in rats. In the defensi ve burying paradigm simultaneous blockade of MR and GR increased immob ility behavior, whereas a small decrease in defensive burying was seen . In the fear-potentiated startle test concurrent MR and GR blockade l ed to an increase in fear-potentiated startle at the highest loudness level (105 dB). In both tests the antagonists were not effective when given separately. The findings are discussed in terms of the involveme nt of CR and MR in neural mechanisms of fear and anxiety.