Haloperidol and aripiprazole affects CRH system and behaviour of animals exposed to chronic mild stress

CRH system integrates responses to stress challenges, whereas antipsychotics may impinge on this process. Effect of haloperidol (HAL) and aripiprazole (ARI) on chronic mild stress (CMS) induced neurobehavioral and CRH/CRHR1 system changes was studied in functionally interconnected rat brain areas including prefrontal cortex (PFC), bed nucleus of the stria terminalis (BNST), hypothalamic paraventricular nucleus (PVN), hippocampus (HIP), and amygdala (AMY). Animals were exposed to CMS for 3-weeks and since the 7th day of CMS injected with vehicle (VEH), HAL (1 mg/kg) or ARI (10 mg/kg) for 4-weeks. Expression levels of CRH, CRHR1, and c-fos genes and anxiety-like and anhedonia behavioural patterns were evaluated. CMS in VEH animals suppressed CRH gene expression in the PFC and BNST, c-fos expression in all areas, except HIP, and increased CRHR1 gene expression in the HIP. Antipsychotics decreased CRH gene expression in all areas, except HIP and by CMS elevated CRHR1 expression in the HIP (ARI also in AMY). CMS and antipsychotics decreased the sucrose preference. Aripiprazole prevented CRH expression decrease in the BNST and sucrose preference induced by CMS. Haloperidol increased time spent in the EPM open arms. These data indicate that HAL and ARI selectively influenced behavioural parameters and CRH/CRHR1 gene expression levels in CMS animals.

Microbiota affects the expression of genes involved in HPA axis regulation and local metabolism of glucocorticoids in chronic psychosocial stress

The commensal microbiota affects brain functioning, emotional behavior and ACTH and corticosterone responses to acute stress. However, little is known about the role of the microbiota in shaping the chronic stress response in the peripheral components of the hypothalamus-pituitary-adrenocortical (HPA) axis and in the colon. Here, we studied the effects of the chronic stress-microbiota interaction on HPA axis activity and on the expression of colonic corticotropin-releasing hormone (CRH) system, cytokines and 11β-hydroxysteroid dehydrogenase type 1 (11HSD1), an enzyme that determines locally produced glucocorticoids. Using specific pathogen-free (SPF) and germ-free (GF) BALB/c mice, we showed that the microbiota modulates emotional behavior in social conflicts and the response of the HPA axis, colon and mesenteric lymph nodes (MLN) to chronic psychosocial stress. In the pituitary gland, microbiota attenuated the expression of Fkbp5, a gene regulating glucocorticoid receptor sensitivity, while in the adrenal gland, it attenuated the expression of genes encoding steroidogenesis (MC2R, StaR, Cyp11a1) and catecholamine synthesis (TH, PNMT). The pituitary expression of CRH receptor type 1 (CRHR1) and of proopiomelanocortin was not influenced by microbiota. In the colon, the microbiota attenuated the expression of 11HSD1, CRH, urocortin UCN2 and its receptor, CRHR2, but potentiated the expression of cytokines TNFα, IFNγ, IL-4, IL-5, IL-6, IL-10, IL-13 and IL-17, with the exception of IL-1β. Compared to GF mice, chronic stress upregulated in SPF animals the expression of pituitary Fkbp5 and colonic CRH and UCN2 and downregulated the expression of colonic cytokines. Differences in the stress responses of both GF and SPF animals were also observed when immunophenotype of MLN cells and their secretion of cytokines were analyzed. The data suggest that the presence of microbiota/intestinal commensals plays an important role in shaping the response of peripheral tissues to stress and indicates possible pathways by which the environment can interact with glucocorticoid signaling.