The influence of polyI:C during different stages of pregnancy on the development of psychiatric disorders in offspring

Abstract

Psychiatric disorders are known for their high disease burden, even though it is still uncertain what exactly causes these disorders. However, it is known that environmental factors such as infections can largely influence the developing brain. Previous studies have shown that maternal infections during pregnancy increase the risk of psychiatric disorders in offspring, but many specifics still remain to be unravelled. It is important to gain more knowledge about this subject in order to improve treatment and prevention of psychiatric disorders. In the current paper, the influence of polyI:C injections in pregnant rats on the development of psychiatric disorders in offspring is assessed. We compare two different stages of pregnancy; gestational day (GD) 9 - corresponding to the first trimester in humans - and GD15 - corresponding to the second trimester. The offspring is analysed based on heart rate variability (HRV) and ultrasonic vocalizations (USV) on postnatal days 7 and 14. The difference in bandwidth of USV’s, as a measure for the complexity of USV’s, showed a significant interaction between the treatment day of the pregnant rat and the sex of the offspring. Specifically, there was a difference between males and females for treatment at GD9, with a p-value of 0,004. Other than that, no significance was found in any variables in both the HRV and the USV measurements. However, non-significant correlations in mainly the USV data suggested a difference for the interaction of sex and treatment day. Possibly polyI:C at GD9 affects males more, while polyI:C at GD15 affects females more. Possibly there are differences between male and female rat pups regarding HRV and USV’s. No significance could be found in the current research to support this idea, but slight differences have been observed. Combined with previous research this does indicate that differences could be present. Further research is warranted to establish the relationship between the sex of the offspring and different moments of maternal immune activation during pregnancy.