Stress-activated hormonal response following predator stress mediates the precipitation of long lasting changes in affective behavior in rats

Muir, Christopher Alan (2007) Stress-activated hormonal response following predator stress mediates the precipitation of long lasting changes in affective behavior in rats. Masters thesis, Memorial University of Newfoundland.

[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (2MB)

Abstract

The role of β-adrenoreceptors, glucocorticoid receptors (GRs), and mineralocorticoid receptors (MRs) in the consolidation of changes in anxiety-like behavior following predator stress were studied by injecting specific receptor blockers 1 minute after the stress event and testing for behavior change in a battery of tests 1 week later. Propranolol dose dependently blocked stress effects in all behavior tests except startle. GR block (RU486) alone was ineffective, but in combination with low dose propranolol blocked stress-induced anxiety-like behavior in all tests. Surprisingly, MR block (spironolactone) also prevented the consolidation of anxiety-like behavior in all tests except the light-dark box. -- Startle results were complicated by the presence of both stress-induced increases and decreases in peak startle amplitude. Treatment with chlordiazepoxide and RU486 effectively blocked startle suppression, but not enhancement, indicating that the consolidation of these two memory processes may be mediated by different mechanisms. In contrast, when administered in combination with propranolol, RU486 prevented stress-induced startle enhancement, as did MR block using spironolactone. -- Predator stress delayed habituation to startle in all rats. This was blocked by post-stress treatment of spironolactone, chlordiazepoxide, and RU486 + propranolol in combination, but not by RU486 or propranolol given alone. -- Present findings indicate that consolidation of predator stress-effects share neurochemical mechanisms in common with fear conditioning models, and are relevant to the study of stress-induced changes in affect in humans.

Actions (login required)

View Item