Sensitization is also characteristic of models that minimize habituation, such as CVS. ACTH and corticosterone responses to novel stressors are augmented in CVS animals (e.g., see Ulrich-Lai et al., 2007). As noted, habituating and non-habituation stress regimens differ with respect to baseline endpoints (body weight, resting corticosterone, adrenal weight and/or thymus weight), but data comparing effects on the magnitude of sensitization are lacking. Thus, it is not known whether or not unpredictable regimens elicit more profound sensitization of the HPA axis.
