The Effects of Thimerosal on Astrocytes Cell Number and Synaptic -Related Genes in the Prefrontal Cortex of Male Rats

Today, Thimerosal is used as a preservative in vaccines, pharmaceutical and ‎health products. There is limited and conflicting information about the effects of this ‎substance on the structure of cortical synapses. The aim of this study was to investigate the ‎effects of Thimerosal on genes and molecules involved in the structure and function of ‎synaptic connectivity, the number of astrocytes, and neurons in the prefrontal cortex of ‎male rats.

In this experimental study, 18 male rats were randomly divided into three groups: 1) experimental group receiving a dose of 3000 µg/kg Thimerosal on days 7, 9, 11, and 15 after birth, 2) solvent group receiving phosphate-buffered saline according to the same pattern, and 3) control group receiving no injection. In the fourth week after birth, samples from the prefrontal cortex were collected for immunohistochemical, histological, and molecular studies. One - way analysis of variance (ANOVA) and LSD test were used to determine statistically significant differences between the groups, and the data were expressed as Mean ± SD.

The results of this study revealed a significant decrease in the expression levels of Cadherin-8 (0.18 ± 0.079) and Synapsin-1 (0.36 ± 0.12) genes in the Thimerosal-exposed group compared to both control group (1 ± 0.01 for Cadherin-8 and 1 ± 0.009 for Synapsin-1) and solvent group (0.91 ± 0.097 for Cadherin-8 and 0.84 ± 0.10  for Synapsin-1) (p < 0.001). Furthermore, there was a significant decrease in the number of astrocytes in the Thimerosal - exposed group (10.66 ± 1.86) compared to the control group (6.43 ± 1.01) and the solvent group  (6.93 ± 1.39), as well as a decrease in the number of neurons (194.66 ± 19.59) compared to the control group (267.99 ± 10.19) and the solvent group (252.33 ± 23.06) (p < 0.01).

It seems that Thimerosal causes abnormal changes in the expression levels of genes ‎involved in the function and structure of synapses. Prolonged exposure to Thimerosal may lead to neurodevelopmental disorders.