The adreno-cortical hormones ,are considered one of the most important parts of the nonspecific reaction of the organism to different stress effects including the stress induced analgesia . This paper is interested in the study of the effect of repeated cold stress(swimming in cold water ١٧ c for ten minutes) and the emotional stress (immobilization for ten minutes) for the average of six times daily for six days,(on the test of tail flick latency) in normal and adrenalectomized rats . The aim is to know the analgesic system and their probable relation wth the adreno-cortical hormones . As the normal and adrenalectomized rats are subject to cold stress, they are analgesic after the first and the last test during six days.The adrenalectomized rats are characterized by a mor important analgesia, which lasts for a longer time after the first and last stress compared with the normal animals,but contrary to the latest, the continuos response after the last stress is longer than the one after the first stress.When the normal rats are subject to emotional stress , this will cause hyperalgesia which disappears progressively and then completely after the six stress and the first value will be constant until the end of the experience.On the other hand the adrenalectomized rats are analgesic after the sixth stress of the first day and this will reach a climax on the third day and back to normal in the last day of the experiment. The injection of morphine to the rats (١٠mg\kg) shows that its analgesic effect on the adrenalectomizd rats (control) lasted for a longer time compared with the normal animals(control).Any difference in the analgesic effect of the morphine was observed in the normal animals while this analgesic effect decreases in the adrenalectomized rats when they subject to repeated stress. These results show that the cold stress is inducing opioid and non opioid analgesia systems.The adreno-cortical hormones induced by stress can control analgesia by affecting the opioid system.The emotional stress leads to opioid analgesic systems which are affected by the cortical steroids hormones. This could be responsible for hyper sensibility induced by emotional stress.
Key words: Cold stress-Emotional stress-Analgesia- Adrenalectomy-Morphine-Adreno-Cortical hormones.