The direct regulation of feeding-driving hypothalamic GABAergic neurons on stress responses

Project Summary To develop effective therapies against the stress-related mental disorders (i.e., PTSD), it is highly important to fully understand neural basis and mechanisms that underlie stress responses. The properly orchestrated activity dynamics of corticotropin-releasing hormone (CRH) neurons in the paraventricular nucleus of hypothalamus (PVH, denoted as PVHCRH neurons), the apex of the hypothalamic-pituitary-adrenal (HPA) axis, are very important for underlying normal stress responses. PVHCRH neuronal activity is well known to be closely controlled by a complex of stimulatory and inhibitory actions imposed by upstream GABAergic and glutamatergic inputs as well as other hormonal and synaptic inputs. Despite the stress responses are well understood at the level of PVHCRH neurons, very little is known about how stress signals are directly triggered, buffered and regulated by upstream neurons that send direct inputs to PVHCRH neurons. Our pilot study showed that arcuate nucleus (Arc) GABAergic neurons (denoted as ArcGABA neurons) represent one major presynaptic GABAergic source of PVHCRH neurons (Notably, the AgRP subset of ArcGABA neurons has been shown DO NOT sending direct inputs to PVHCRH neurons). Our preliminary tests further found that ArcGABA neurons a) inversely regulate PVHCRH neuronal activity in a time-locked manner, b) respond in a stark contrast phase with PVHCRH neurons but in the same phase with GABA release onto PVHCRH neurons in response to the same stressor, and c) drive stress level in an opposite direction to PVHCRH neurons. Based on these compelling findings, we hypothesize that feeding-driving ArcGABAergic neurons are the anatomical and functional upstream of PVHCRH to directly . To test this hypothesis, the combination of in vivo fiber photometry, fluorescent intensity-based neurotransmitter sensors, RetroLEAP (retrograde transsynaptic Labelling, Expression And Perturbation), intersectional Cre-loxP/FRT-FlpO genetic approaches neurons regulate stress responses and the ethologically relevant behavioral tests will be used in this proposal. Specifically, we will test whether inputs from ArcGABA neurons directly drive PVHCRH vivo activity changes in ArcGABA neurons directly shape balance between feeding behaviors and stress responses to stressor the PVHCRH-HPA axis responsivity responses in animals exposed to (Aim1). We will also test whether in and regulate predator stress while the foraging for food (Aim 2). The expected findings will functionally bridge feeding-driving ArcGABA neurons with stress- responsive PVHCRH neurons, thereby providing significant information to understand a novel brain mechanism underlying the integrative control of adaptive feeding behaviors and stress responses.