Background
The authors' previous study showed a closed-loop chip system that was used to control arterial pressure in normal rabbits and rats. In the present study the anti-hypertensive effects of the chip system were investigated in anaesthetized two-kidney one-clip (2K1C) renovascular hypertensive rats and compared with sham-operated rats.
Material and Method
The chip system recorded, sampled, and processed the signals of arterial pressure and instantaneously controlled arterial pressure by stimulating the left aortic depressor nerve. The frequency of stimulation was determined according to the feedback signals of arterial pressure.
Results
The chip system, running three different programs, successfully achieved a different degree of depressor effects. It effectively decreased not only mean arterial pressure (MAP), but also renal sympathetic nerve activity (RSNA) in both 2K1C rats and sham-operated rats. The chip system significantly increased the baroreflex gain in the 2K1C rats, but not in the sham-operated rats. It normalized the increased left ventricle developing pressure and maximal rise rate of the left ventricle pressure (dP/dtmax) in the 2K1C rats.
Conclusions
These results indicate that the depressor effect can be controlled by changing the programs of the chip system. The closed-loop chip system effectively decreased arterial pressure and sympathetic outflow, increased baroreflex gain, and normalized the enhanced cardiac contractility in renovascular hypertensive rats.

Keywords: Renal Circulation - physiology, Sympathetic Nervous System - physiopathology, Rats, Inbred SHR, Myocardial Contraction - physiology, Implants, Experimental, Hypertension - therapy, Electric Stimulation, Blood Pressure - physiology, Baroreflex - physiology