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

Abstract

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.

Predator threat induces behavioral inhibition, pituitary-adrenal activation and changes in amygdala CRF-binding protein gene expression

“…Consistent with previous studies using cat odor as a stimulus (Dielenberg et al, 2001;McGregor et al, 2004) we found that 10 min of ferret exposure resulted in a robust increase in the number of Fos-positive cells within the MeA. Similarly, c-fos mRNA was increased in the MeA of rats immediately after a 30 min exposure to ferret odor (Masini et al, 2005). The MeA, which lies medial to the CeA, showed the largest increase in c-fos expression within the amygdala and is of interest because earlier studies associated it with fear and defensive responses (Kemble et al, 1984).…”

“…Similarly, exposure to the odor of a ferret has been reported to increase rat corticosterone levels (Masini et al, 2005). In the present study corticosterone concentrations peaked 15 min after cessation of 10 min of ferret exposure and returned to baseline by 120 min.…”

“…In addition, exposure to cat odor failed to increase BLA c-fos expression (Dielenberg et al, 2001), but in another study exposure to red fox odor increased BLA c-fos expression (Funk and Amir, 2000). Lastly, c-fos mRNA levels increased immediately following a 30 min exposure to ferret odor (Masini et al, 2005). Our studies demonstrate an increase in c-fos expression in the BLA in response to ferret exposure, suggesting a role for the BLA in mediating the response to ferret predator threat.…”

“…Few studies have examined c-fos expression in the lateral hypothalamus following predator exposure and none have examined the time course for induction of c-fos expression. One study showed that cat odor failed to increase c-fos expression in the lateral hypothalamus (Dielenberg et al, 2001); whereas, other studies have shown that both fox odor and ferret odor (Masini et al, 2005) failed to increase c-fos expression in the lateral hypothalamus.…”

“…Some studies suggest that the CeA is not involved in unconditioned fear responses as indicated by a lack of an effect of CeA lesions on rat freezing behavior elicited by cat or fox odor (Fendt et al, 2003;Li et al, 2004;Rosen, 2004). In terms of c-fos expression, studies have demonstrated no increase in cfos expression in the CeA following exposure to cat odor (Dielenberg et al, 2001) or ferret odor (Masini et al, 2005); whereas, another study reported a significant increase in the number of Fos-positive cells in the CeA in rats following fox odor exposure . We demonstrate that acute ferret exposure results in a time-dependent increase in the number of Fos-positive cells in the CeA.…”