[DIFFERENCES IN ADAPTIVE BEHAVIORS IN ADOLESCENT MALE AND FEMALE RATS EXPOSED AS NEWBORNS TO INFLAMMATORY PAIN OR STRESS].

In adolescent rats (25-35-day-old) exposed as newborns (the first and repeatedly second days) to adverse impacts (inflammatory pain, stress of short-term maternal separation or their combination) sex dimorphism was revealed in pain behavior under conditions of similar peripheral inflammation. According to the priority data obtained, strengthening of pain-related response in the formalin test was found in males, whereas pain sensitivity in females was not changed, that is pain experienced by them as newborns did not affect the system reactivity to the same chemical irritant in the adolescent period. However, the rats of both sexes, who experienced short-term stress of maternal deprivation (60 min-during the first and the second days of life), displayed increased pain sensitivity in the formalin test. Combined effect of inflammatory pain and maternal deprivation in newborns did not alter pain sensitivity in both adolescent males and adolescent females. The male and female rats exposed as newborns to maternal deprivation displayed a decrease of the anxiety level in the elevated plus maze; the rats, exposed to each of the above-mentioned early impacts showed a decline of adaptive behavior in the forced swimming test; the males exposed to pain and combined impacts demonstrated impairment of spatial learning in Morris labyrinth. Thus, we pioneered in demonstrating sex differences in the effects of inflammatory pain in newborn pups on pain sensitivity in the formalin test in adolescent rats. Separation of the influence of early stress or pain was revealed in adolescent females in the formalin test: maternal deprivation induced hyperalgesia, whereas pain failed to change functional activity of the tonic nociceptive system.