Investigation of the relationship between microglial activation and behavior in adolescent rats with experimental infection model

Objective: In a lipopolysaccharide-induced neuroinflammation model in early adolescence, we aimed to investigate whether the medial prefrontal cortex of rats would affect microglia count, synapse plasticity, schizophrenia, and similar behavioral change in adulthood. Material-Method: 20 27-day-old male Wistar rats were divided into two groups and one animal per cage was caged with 8+2 animals. Neuroinflammation was induced by administration of 0,5 mg/kg intraperitoneal lipopolysaccharide on days 31, 33, 35, 37, and 39 after birth, and their weight was weighed and recorded on the first and tenth days. 24 hours after the last injection, two animals from the groups were sacrificed. All remaining animals were tested on day 63 postnatal with new tests of object recognition, social interaction, and open space behavior. After the behavioral tests, the brain tissues were collected by sacrificing with the transcardial perfusion method. The adult medial prefrontal cortex was evaluated using hematoxylin-eosin, ionized calcium-binding adapter protein, and primary antibodies to postsynaptic density protein. Results: Lipopolysaccharide reduced weight gain during injection administration. In adulthood, it reduced locomotor activity and did not affect anxiety or object recognition. It reduced social interaction, but no significant differences were found between the groups. In the adult medial prefrontal cortex, positively stained PSD-95 reduced cell count and microglia count, while H&E staining showed that pyramidal neurons experienced cell shrinkage and had pyknotic nuclei. In the adolescent medial prefrontal cortex, the number of microglia is reduced. Conclusions: It was determined that immune intervention during adolescence may adversely affect the number of microglia, behavior, and synaptic plasticity in adulthood. Behavior, microglia, and changes in PSD-95 levels have been hypothesized to be due to lipopolysaccharide. Key Words: Rat, Neuroinflammation, Adolescent, Microglia, Behavior, Schizophrenia, Iba-1, PSD-95