Corticosterone Increases Depression-Like Behavior, With Some Effects on Predator Odor-Induced Defensive Behavior, in Male and Female Rats.

This experiment examined the effect of repeated corticosterone injections on anxiety and depression-like behavior in male and female rats. Rats received either corticosterone or vehicle injections for 21 consecutive days prior to behavioral testing in the forced swim, open-field, and predator odor tests. The corticosterone injections significantly increased depression-like behavior in the forced swim test in both male and female rats but had no significant effect on anxiety in the open-field test. In the predator odor test, the corticosterone injections significantly increased a subset of defensive behaviors in the male rats. These results suggest that repeated exposure to corticosterone increases depression-like behavior, with some effects on anxiety, and that male rats may be more affected than female rats by this manipulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Role of Hippocampal Regions CA3 and CA1 in Matching Entorhinal Input With Retrieval of Associations Between Objects and Context: Theoretical Comment on Lee et al. (2005).

Models of hippocampal function have proposed different functions for hippocampal regions CA3 and CA1, commonly proposing that CA1 performs a match-mismatch comparison of memory retrieval with sensory input. The study by I. Lee, M. R. Hunsaker, and R. P. Kesner (2005) tested these models using selective lesions of hippocampal subregions (see record 2005-01705-014). Their data suggest that CA3 and the dentate gyrus play an important role in the process of detecting the mismatch when a familiar object is placed in a new spatial location. Lesions of the dentate gyrus and CA3 strongly reduce the enhanced exploration associated with displaced objects, beyond the reduction caused by CA1 lesions. This supports the importance of convergent input to CA3 as well as CA1. Along with recent electrophysiological data, this provides a framework for more specifically modeling the role of CA3 and CA1 in matching sensory input with context-dependent retrieval for memory-guided behavior in different tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ferret Odor as a Processive Stress Model in Rats: Neurochemical, Behavioral, and Endocrine Evidence.

Predator odors have been shown to elicit stress responses in rats. The present studies assessed the use of domestic ferret odor as a processive stress model. Plasma corticosterone and adrenocorticotropin hormone levels were higher after 30 min of exposure to ferret odor (fur/skin) but not control odors, ferret feces, urine, or anal gland secretions. Behavioral differences were also found between ferret and the control odors as tested in a defensive withdrawal paradigm. In addition, c-fos messenger RNA expression in several brain areas previously associated with processive stress was significantly higher in ferret odor-exposed rat brains than in control odor-exposed brains. These results suggest that ferret odor produces a reliable unconditioned stress response and may be useful as a processive stress model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)