Anxiety stress and nociceptive responses in mice.

Nociception in laboratory animals appears to be influenced by physical or emotional stressors. Nevertheless, the reported data are not univocal. Discrepancies seem to be caused by some kind of stress model and/or by the timing of stressor application. The aim of the present work is to study the influence of chronic application of a well-controlled and defined anxiety stress paradigm (rotational stress) on the behavioral formalin pain responses in mice maintained in a low-stress environment. The results indicate that emotional chronic stress increases specific pain responses in the late inflammatory phase and, correspondingly, decreases self-grooming. Locomotor activity appears influenced by pain presence only. The hormonal and neural mechanisms that could be involved in the observed nonspecific and specific nociceptive responses to stress are discussed.