The Effects of Early Exposure to Thimerosal on Impairments of Social and Stereotyped Behaviors and the Number of Purkinje Cells of Cerebellum in Rats

Existing evidence on the impact of thimerosal (THIM), acting to preserve pharmaceutical products (a preservative), on fetal neurodevelopment is very controversial. Here, we investigated the neonatal administration of THIM on behaviors including (1) locomotor activity, (2) social behaviors, and (3) stereotyped behaviors in rats. Since the development of cerebellum continues for some time after birth and it is very imperative in movement, balance, and sensory integration, the number of cerebellum Purkinje cells also were counted. The experiments were directed on 40 young male and female Wistar rats, which were randomly distributed into 4 groups including experimental (male & female) and control (male & female) groups. Each rat in the test groups were intramuscularly received 240 μg Hg/kg THIM on postnatal days (7, 9, 11, 15), while the control contributors received saline in the same pattern. After drug interventions on the fourth postnatal week, rats were evaluated by open field test, and in eighth postnatal week, the test of three-chamber paradigm was performed on animals. At the end of the behavioral tests, histological studies were done. Rats which were exposed to the THIM displayed impairments of locomotor activity and their social interactions were reduced. While the duration of freezing/grooming as stereotyped behaviors were increased significantly. The results of histological studies also showed a noteworthy decrease in the number of Purkinje cells in both sexes. These data prove that early postnatal exposure of children to THIM causes permanent neurobehavioral and histological impairments and if similar alterations occur in children exposed to THIM/mercurial agents, neurodevelopmental disorders may happen.