Chloride homeostasis dysfunction drives hyperactivation of corticotropin-releasing factor-expressing neurons in the amygdala in stress-induced hypertension

Stress promotes the progression from borderline hypertension to sustained hypertension, but the mechanism remains unclear. We investigated the role of corticotropin-releasing factor (CRF)-expressing neurons in the central nucleus of amygdala (CeA) on arterial blood pressure (ABP) and sympathetic activity of borderline hypertensive rats (BHRs) subjected to chronic unpredictable mild stress (CUMS). CUMS induced sustained hypertension, and led to increased delta-FosB expression as well as enhanced spontaneous and evoked firing of CeA CRF-expressing neurons in BHRs. Furthermore, optogenetic activation of CeA CRF-expressing neurons significantly increased the sympathetic outflow and ABP in BHRs. Impaired GABAergic inhibition, a depolarizing shift of GABA reversal potential (EGABA), disrupted chloride homeostasis and increased NKCC1 expression were observed in CeA CRF-expressing neurons in BHRs subjected to CUMS. NKCC1 inhibition with bumetanide restored GABAergic inhibition and chloride homeostasis, normalized neuronal excitability, leading to reduced sympathetic vasomotor tone in CUMS BHRs. These results indicate that NKCC1-mediated disruption of chloride homeostasis in CeA CRF-expressing neurons contributes to elevated sympathetic activity and hypertension under chronic stress. These findings enhance our understanding of the neuronal and molecular mechanisms underlying stress-induced hypertension and reveal potential targets for its prevention and treatment.