PERINATAL EXPOSURE TO A LOW-DOSE OF DIOXIN INDUCES DEFICITS IN FEAR CONDITIONING IN MICE

摘要

In utero and lactational exposure to dioxins have been reported to affect brain functions of the offspring even when the exposure level is too low to affect their dams. We investigated the effects of the perinatal exposure to a low-dose of 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) on the fear memory in mouse offspring. Pregnant C57BL/6J mice were given by gavages TCDD at a dose of 0, 0.6, 3.0 μg/kg, and their male offspring were used for the behavioral test. In the fear conditioning, three tone-footshock pairings were presented. Retention tests for the contextual and auditory fear memory were carried out 1 h after conditioning. The offspring born to dams exposed to 0.6 μg/kg of TCDD showed a significant decrease in freezing response in the contextual, but not the auditory, retention test. On the other hand, the perinatal 3.0 μg/kg of TCDD-exposed group showed deficits in both the contextual and auditory retention tests. The results indicate the perinatal exposure to a low-dose of dioxin disrupted the functions of the memory and emotion in the male mouse offspring.