Resetting blood pressure by a closed-loop implanted chip system in normotensive rats.

A closed-loop implanted chip system was designed to control blood pressure without using drugs. The chip system instantaneously reset blood pressure by stimulating the left aortic depressor nerve according to the feedback signals of arterial blood pressure. The relationship between pressure signals and frequency of stimulation was identified in vitro and in vivo, and the efficiency of the chip system was evaluated in normal anesthetized Wistar rats. To determine whether the depressor effect of the chip was primarily independent on the bradycardia induced by the resetting, the effects of methyl atropine (1.5 g/kg, iv.) and bilateral vagotomy on depressor effect induced by the chip system were determined, respectively. The results indicated that the chip system worked well. The frequency of stimulus linearly increased following the elevation of pressure from 70 to 160 mm Hg. The frequency of the stimulus reached its maximum (100 Hz) when pressure exceeded 160 mm Hg, and the stimulation stopped when MAP was below 70 mm Hg. There were significant decreases in mean arterial pressure (MAP, -20.0+/-4.4 mm Hg) and heart rate (HR, -43.0+/-10.5 bpm) during the resetting in rats. After resetting, both MAP and HR recovered in a minute without any significant rebound. Pretreatment with either methyl atropine or bilateral vagotomy abolished the bradycardia effect but produced no significant effect on hypotension. The results demonstrated that the chip system successfully reset blood pressure in rats, and that the hypotension induced by the chip system was primarily independent on the bradycardia effect.