Endogenous corticotropin-releasing factor potentiates the excitability of presympathetic neurons in paraventricular nucleus via activation of its receptor 1 in spontaneously hypertensive rats.

It is well established that increased excitability of the presympathetic neurons in the hypothalamic paraventricular nucleus (PVN) during hypertension leads to heightened sympathetic outflow and hypertension. However, the mechanism underlying the overactivation of PVN presympathetic neurons remains unclear. This study aimed to investigate the role of endogenous corticotropin-releasing factor (CRF) on the excitability of presympathetic neurons in PVN using Western blot, arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) recording, CRISPR/Cas9 technique and patch-clamp technique. The results showed that CRF protein expression in PVN was significantly upregulated in spontaneously hypertensive rats (SHRs) compared with normotensive Wistar-Kyoto (WKY) rats. Besides, PVN administration of exogenous CRF significantly increased RSNA, heart rate and ABP in WKY rats. In contrast, knockdown of upregulated CRF in PVN of SHRs inhibited CRF expression, led to membrane potential hyperpolarization, and decreased the frequency of current-evoked firings of PVN presympathetic neurons, which were reversed by incubation of exogenous CRF. Perfusion of rat brain slices with artificial cerebrospinal fluid containing CRF receptor 1 (CRFR1) blocker, NBI-35965, or CRF receptor 2 (CRFR2) blocker, Antisauvagine-30, showed that blocking CRFR1, but not CRFR2, hyperpolarized the membrane potential and inhibited the current-evoked firing of PVN presympathetic neurons in SHRs. However, blocking CRFR1 or CRFR2 did not affect the membrane potential and current-evoked firing of presympathetic neurons in WKY rats. Overall, these findings indicate that increased endogenous CRF release from PVN CRF neurons enhances the excitability of presympathetic neurons via activation of CRFR1 in SHRs.

Corticotropin-releasing factor potentiates glutamatergic input and excitability of presympathetic neurons in the hypothalamus in spontaneously hypertensive rats.

Hyperactivity of presympathetic neurons in the hypothalamic paraventricular nucleus (PVN) plays a key role in generating excess sympathetic output in hypertension. However, the mechanisms driving hyperactivity of PVN presympathetic neurons in hypertension are unclear. In this study, we determined the role of corticotropin-releasing factor (CRF) in the PVN in augmented glutamatergic input, neuronal excitability and sympathetic outflow in hypertension. The number of CRF or c-Fos immunoreactive neurons and CRF/c-Fos double-labeled neurons in the PVN was significantly greater in spontaneously hypertensive rats (SHRs) than in normotensive Wistar-Kyoto (WKY) rats. Blocking glutamatergic input reduced the CRF-potentiated excitability of spinally projecting PVN neurons. Furthermore, CRF knockdown via Crispr/Cas9 in the PVN decreased the frequencies of spontaneous firing and miniature excitatory postsynaptic currents (mEPSCs) in spinally projecting PVN neurons in SHRs. In addition, the mRNA and protein levels of CRFR1, but not CRFR2, in the PVN were significantly higher in SHRs than in WKY rats. Blocking CRFR1 with NBI-35965, but not blocking CRFR2 with Antisauvagine-30, reduced the frequencies of spontaneous firing and mEPSCs of spinally projecting PVN neurons in SHRs. Also, microinjection of NBI-35965 into the PVN significantly reduced arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) in anesthetized SHRs, but not in WKY rats. However, microinjection of Antisauvagine-30 into the PVN had no effect on ABP or RSNA in WKY rats and SHRs. Our findings suggest that endogenous CRF in the PVN potentiates glutamatergic input and firing activity of PVN presympathetic neurons via CRFR1, resulting in augmented sympathetic outflow in hypertension.