Dysregulated <scp>HPA</scp> axis during postnatal developmental stages in the <scp>BTBR</scp><i>T⁺ Itpr3^tf/</i>J mouse: A model of autism spectrum disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder. Some children with ASD show enhanced cortisol response to stress. BTBR T⁺ Itpr3^tf/J (BTBR) mice, an ASD model, display behavior consistent with the three diagnostic categories of ASD and exhibit an exaggerated response to stress in adulthood. However, it remains unclear how basal corticosterone levels change and how the hypothalamic-pituitary-adrenal axis responds to stress during the early life stages in BTBR mice. In this study, we found that basal corticosterone levels showed characteristic changes, peaking at weaning during postnatal development in both BTBR and control C57BL/6J (B6J) mice. Furthermore, we observed higher corticosterone and corticotropin-releasing hormone levels in BTBR mice than in B6J mice following acute stress exposure during weaning; however, adrenocorticotropic hormone levels were lower in BTBR mice. Glucocorticoid receptor mRNA expression levels in the hippocampus and lateral septum after stress were higher in BTBR mice than in B6J mice. This study documented changes in corticosterone levels at baseline during postnatal development in mice and showed that BTBR mice exhibited disrupted stress responses at weaning.