The GABA(B1) receptor within the infralimbic cortex is implicated in stress resilience and vulnerability in mice

Abstract

Resilience is the capacity to maintain normal psychological and physical functions in the face of stress and adversity. Understanding how one can develop and enhance resilience is of great relevance to not only promoting coping mechanisms but also mitigating maladaptive stress responses in psychiatric illnesses such as depression. Preclinical studies suggest that GABA(B) receptors (GABA(B1) and GABA(B2)) are potential targets for the treatment of major depression. In this study, we assessed the functional role of GABA(B) receptors in stress resilience and vulnerability by using a chronic unpredictable stress (CUS) model in mice. As the medial prefrontal cortex (mPFC) plays a key role in the top-down modulation of stress responses, we focused our study on this brain structure. Our results showed that only approximately 41.9% of subjects exhibited anxiety- or despair-like behaviors after exposure to CUS. The vulnerable mice showed higher c-Fos expression in the infralimbic cortex (IL) subregion of the mPFC when exposed to a social stressor. Moreover, the expression of GABA(B1) but not GABA(B2) receptors was significantly downregulated in IL subregion of susceptible mice. Finally, we found that intra-IL administration of baclofen, a GABA(B) receptor agonist, rapidly relieved the social avoidance symptoms of the "stress-susceptible" mice. Taken together, our results show that the GABA(B1) receptor within the IL may play an important role in stress resilience and vulnerability, and thus open an avenue to develop novel, personalized approaches to promote stress resilience and treat stress-related psychiatric disorders.

Keywords: Chronic unpredictable stress; GABA(B) receptors; Infralimbic cortex; Medial prefrontal cortex; Resilience.