GENDER AND TEST DEPENDENCE OF A TYPE OF KAPPA MEDIATED STRESS-INDUCEDANALGESIA IN MICE

1. In male mice, 80 inescapable footshocks (5-80) induce analgesic res ponses measured by the tail flick test that are blocked by naloxone an d the kappa opioid antagonist, nor-binaltorphimine. We now study the n ociceptive responses, induced after this particular stress, measured b y the writhing test, the tail immersion test and a high intensity tail immersion test both in male and female mice. 2. In stressed males, an algesic responses are seen in all the nociceptive tests. Naloxone (10 mg/kg) does not prevent them. 3. In stressed females, in contrast with males, no analgesia is produced in the tail flick test. The writhing test and the tail immersion test registered analgesic responses that w ere not prevented by naloxone (to mg/kg). 4. We conclude that only the antinociceptive kappa opioid mediated component of the stress we stud y is strongly dependent on gender, in contrast to other types of analg esia triggered by the same stress.