Stress hyperalgesia in rats: an experimental animal model of anxiogenic hyperalgesia in human.

Emotional, non-noxious stress consisting of inescapable holding or exposure to novelty were found to produce clearcut and reproducible hyperalgesia in the rat. The mechanisms of the two stress hyperalgesia appeared to be different: 1) hypophysectomy enhanced holding hyperalgesia but reduced novelty hyperalgesia, indicating that pituitary factors respectively compensate (through opioids ?) and participate (through ACTH ?) in stress hyperalgesia; 2) diazepam did not alter holding hyperalgesia but abolished novelty hyperalgesia. The two types of stress hyperalgesia might represent animal models of anxiogenic hyperalgesia observed in human: as for clinical anxieties, they are alleviated or not by diazepam.