Figure 1.

Experimental design. Pregnant dams were exposed to MIA with LPS (2 mg/kg in 1 mL, subcutaneously) beginning on the 7th (GD7) day of pregnancy and continuing every 2nd day until delivery. Control animals were subjected to vehicle (saline) injections on the same schedule. Twenty-one days after birth (PND21), male offspring were separated from dams and housed in groups of 5 per cage under standard conditions. Prior to further experiments, the rats were divided into 2 cohorts. The offspring from the 1st cohort (both the control and MIA groups) were used only for the behavioural examinations, including the exploratory activity test at PND88, light-dark box test at PND90, forced swim test at PND95 and PPI test at PND100. The animals from the 1st cohort were not included in the biochemical analyses. The offspring from the 2nd cohort (both the control and MIA groups) underwent the behavioural examinations in the following order: the PPI test at PND30 and PND60, the social interaction test at PND90 and the PPI test at PND100. At PND120, the animals were divided into 6 groups (control + vehicle, control + LPS, MIA responsive + vehicle, MIA responsive + LPS, MIA non-responsive + vehicle, MIA non-responsive + LPS) and were exposed to the second hit either with LPS (250 µg/kg in 1 mL, intraperitoneally) or vehicle (saline), according to the group assigned. Two hours later, the rats underwent the PPI test and after another 2 h, they were sacrificed by decapitation. The tissues (the frontal cortices and hippocampi) were collected for the biochemical analyses (qRT-PCR, Western blot and ELISA).