Exposure to the odors of natural predators activates the HPA axis and produces anxiety-like behavior in rats. Acute stress through exposure to trimethylthiazoline (TMT), a component in fox feces, decreases cell proliferation and differentiation of immature neurons in the dentate gyrus (Hill et al., 2006; Kambo & Galea, 2006; Mirescu et al., 2004; Tanapat et al., 2001). This decrease is not due solely to novel odor experience, as other novel odors do not reduce cell proliferation (Tanapat et al., 2001). One study found no change in cell proliferation following predator odor exposure (Thomas et al., 2006), however, as with the social stress study described previously (Thomas et al., 2007), new cells were labeled during the stressful experience, instead of following it, and therefore is not an accurate test of the effects of stress on cell proliferation.
