Social interaction, psychotic disorders and inflammation: A triangle of interest

Influence of antipsychotic drugs on microglia-mediated neuroinflammation in schizophrenia: perspectives in an astrocyte-microglia co-culture model

Schizophrenia is a severe mental disorder with a strong lifetime impact on patients' health and wellbeing. Usually, symptomatic treatment includes typical or atypical antipsychotics. Study findings show an involvement of low-grade inflammation (blood, brain parenchyma, and cerebrospinal fluid) in schizophrenia. Moreover, experimental and neuropathological evidence suggests that reactive microglia, which are the main resident immune cells of the central nervous system (CNS), have a negative impact on the differentiation and function of oligodendrocytes, glial progenitor cells, and astrocytes, which results in the disruption of neuronal networks and dysregulated synaptic transmission, contributing to the pathophysiology of schizophrenia. Here, the role of microglial cells related to neuroinflammation in schizophrenia was discussed to be essential. This review aims to summarize the evidence for the influence of antipsychotics on microglial inflammatory mechanisms in schizophrenia. Furthermore, we propose an established astrocyte-microglia co-culture model for testing regulatory mechanisms and examining the effects of antipsychotics on glia-mediated neuroinflammation. This could lead to a better understanding of how typical and atypical antipsychotics can be used to address positive and negative symptoms in schizophrenia and comorbidities like inflammatory diseases or the status of low-grade inflammation.

Orexins/Hypocretins: Gatekeepers of Social Interaction and Motivation

Ever since the discovery of the brain's orexin/hypocretin system, most research was directed toward unveiling its contribution to the normal functioning of individuals. The investigation of reward-seeking behaviors then gained a lot of attention once the distribution of orexinergic neurons was revealed. Here, we discuss findings on the involvement of orexins in social interaction, a natural reward type. While some studies have succeeded in defining the relationship between orexin and social interaction, the controversy regarding its nature (direct or inverse relation) raises questions about what aspects have been overlooked until now. Upon examining the literature, we identified a research gap concerning conditions influencing the impact of orexins on social behavior expression. In this review, we introduce a number of factors (e.g., stress, orexin's source) that must be considered while studying the role of orexins in social interaction. Furthermore, we refer to published research to investigate the stage at which orexins affect social interaction and we highlight the nucleus accumbens (NAc) shell's role in social interaction and other rewarding behaviors. Finally, the underlying orexin molecular pathway influencing social motivation in particular illnesses is proposed. We conclude that orexin's impact on social interaction is multifactorial and depends on specific conditions available at a time.