Key result
Knockdown of AT1 receptors in the subfornical organ decreased mean arterial pressure and prevented baroreflex dysfunction in two-kidney, one-clip hypertensive rats.
Why the study?
The subfornical organ has been implicated in arterial pressure and baroreflex responses to ANG II, but whether pharmacological inhibition or selective silencing of its AT 1 receptors decreases resting arterial pressure and modulates baroreflex responses in two-kidney, one-clip rats was unknown.
AT1R activation within the subfornical organ contributes to hypertension and baroreflex dysfunction in 2K,1C rats, with gene silencing but not acute pharmacological inhibition reversing these effects.
The subfornical organ (SFO), a forebrain circumventricular organ that lies outside the blood-brain barrier, has been implicated in arterial pressure and baroreflex responses to angiotensin II (ANG II). We tested whether pharmacological inhibition or selective silencing of SFO ANG II type 1 receptors (AT 1 R) of two-kidney, one-clip rats with elevated plasma ANG II decreases resting arterial pressure and renal sympathetic nerve activity (RSNA) and/or modulates arterial baroreflex responses of heart rate (HR) and RSNA. Male Sprague-Dawley rats underwent renal artery clipping [2-kidney, 1-clip (2K,1C)] or sham clipping (sham). After 6 wk, conscious rats instrumented with vascular catheters, renal nerve electrodes, and a cannula directed to the SFO were studied. In another set of experiments, rats were instrumented with hemodynamic and nerve radio transmitters and injected with scrambled RNA or silencing RNA targeted against AT 1 R. Mean arterial pressure (MAP) was significantly higher in 2K,1C rats. Acute SFO injection with the AT 1 R inhibitor losartan did not change MAP in sham or 2K,1C rats. Baroreflex curves of HR and RSNA were shifted rightward in 2K,1C rats. Losartan exerted no effect. SFO AT 1 R knockdown did not influence MAP in sham rats but decreased MAP in 2K,1C rats, despite no change in plasma ANG II or resting RSNA. AT 1 R knockdown prevented the reduction in maximum gain and slope of baroreflex responses of HR and RSNA; the reduced RSNA response to baroreceptor unloading was partially restored in 2K,1C rats. These findings show that AT 1 R activation within the SFO contributes to hypertension and baroreflex dysfunction in 2K,1C rats and highlight the temporal requirement for reversal of these effects.
No takes yet. Share an insight, caveat, or question.
Rossi et al. (2019) studied Hypertension. Pharmacological inhibition (losartan) or selective silencing (siRNA) of SFO AT1 receptors vs. Sham clipping or scrambled RNA was evaluated on Mean arterial pressure and baroreflex responses of heart rate and renal sympathetic nerve activity. Knockdown of AT1 receptors in the subfornical organ decreased mean arterial pressure and prevented baroreflex dysfunction in two-kidney, one-clip hypertensive rats.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: