Correlation between Changes in Stress-Induced Corticosterone Secretion and GR mRNA Levels

The current study was conducted to determine the potential relationship between stress-induced corticosterone secretion and corticosteroid receptor mRNA levels after 5 days of intermittent stress. In particular, we were interested in the rate at which animals terminate a stress response, and how this termination may be altered by repeated stress. Adult male Sprague-Dawley rats were subjected to either 5 days of restraint stress or 5 days of an unpredictable stress paradigm. Restraint-stress induced corticosterone secretion was measured on Days 1 and 5 in both groups, and animals were killed on Day 6. Glucocorticoid receptor (GR), and mineralocorticoid (MR) mRNA levels were determined using in-situ hybridization techniques. Five days of restraint stress caused an habituation of the plasma corticosterone response to stress measured 60 and 90 min post-stress initiation; this pattern of corticosterone secretion was not observed in the animals subjected to unpredictable stress. Five days of either stress paradigm did not alter MR mRNA levels measured within the hippocampus or GR mRNA levels within the hippocampus or the medial parvocellular division of the paraventricular nucleus of the hypothalamus (mpPVN). However, an individual's GR mRNA levels measured within the CA1/2 region of the hippocampus and the mpPVN were significantly correlated with the degree of habituation of the corticosterone response to stress measured on Day 5. This suggests that an increase in the rate of termination of the stress response and levels of GR within the hippocampus and mpPVN may be functionally related.     

Retrieval properties of negative vs. positive mental images and autobiographical memories in social anxiety: outcomes with a new measure

High (n = 41) and low (n = 39) socially anxious (SA) participants completed the Waterloo Images and Memories Interview (WIMI), a new assessment tool that measures the accessibility and properties of mental images and associated autobiographical memories that individuals may experience across both anxiety-provoking (negative) and non-anxiety-provoking (positive) social situations. Results indicated that both high and low SA individuals experience negative images and associated autobiographical memories in anxiety-provoking social situations, but the rates of endorsement of such images and memories among high SA participants were substantially lower than those reported in recent studies. Moreover, whereas low SA individuals were capable of accessing a relatively balanced array of both negative and positive self-representations that were rich in episodic detail, high SA individuals retrieved a higher, more unbalanced ratio of negative-to-positive images and memories, as well as impoverished positive images that were significantly degraded in episodic detail. Finally, negative images influenced the two groups differently, with high SA individuals experiencing more negative emotional and cognitive consequences associated with bringing such images to mind. These results are discussed in relation to theoretical models of learning and memory within the context of contemporary cognitive behavioral models of social anxiety.