The use of morphine as a drug of abuse during pregnancy and lactation induces effects on the developing fetus are still not well elucidated, in which the perinatal exposure to morphine showed increased sensitivity to morphine reinforcement effect in the adult offspring. The present study investigated whether exposure to morphine during pregnancy and lactation can change nociception in adult offspring offspring of mothers treated with morphine. Pregnant female mice were exposed to morphine (10 mg / kg / day) subcutaneously for 42 days (21 days of pregnancy to 21 days of lactation). Upon completion 21 days, the progeny is sexed in males and females, then at 75 days of age, subjected to the open field test and nociception by the methods of writhing induced by acetic acid, hot plate and formalin. In the test of the total locomotion, the animals showed no motor changes. In nociception tests, we observed increased nociceptive response in male mice and female morphine group tested for contortion. Males who have been exposed perinatally to morphine decreased the nociceptive threshold in the second phase (inflammatory phase) of formalin. In the hot plate, the male and female animals showed abnormalities in pain sensitivity, reversing the sensitivity profiles of its controls, in which the group of males exposed perinatally to morphine showed increased sensitivity to thermal stimulus at 120 min test and the group of females exposed perinatally to morphine decreased thermal sensitivity when compared to their controls. These results suggest that exposure to morphine in the intrauterine period and lactation affects nociceptive thresholds in the offspring in later life and that this change is dependent on the type and length of exposure to noxious stimuli.
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