gms | German Medical Science

Objective: We recently demonstrated that selective stimulation of afferent vagal nerve fibers can trigger the baroreflex and lower the blood pressure in rats. In this study we investigate whether the blood pressure recovers to its pre-stimulation value once the stimulation is paused. Prolonged decrease of blood pressure during inter-stimulation periods may pave the way for an energy-efficient technique of solely intermitting selective vagal nerve stimulation as an antihypertensive treatment.

Method: The left vagal nerve bundle of male Wistar rats was isolated and placed in a multichannel cuff electrode (MCE), a micro-tip transducer was inserted in the left carotid artery. After identification of contacts causing the highest decrease of blood pressure several cycles of stimulation with different amplitudes, frequencies and pulse widths were performed. Blood pressure responses were analyzed both in the acute phase during stimulation and over time including the complete study over several hours.

Results: Besides the already known effect of immediate drop of blood pressure during stimulation a secondary, slow slope effect of blood pressure decrease covers most of the stimulation period and beyond. Whenever a selective stimulation was stopped, the blood pressure recovered very slowly to a value just below the initial magnitude. Repetitive stimulation with different parameters therefore caused a sustained lowered blood pressure even with long inter-stimulus-intervals. Since the blood pressure remained unaltered during prolonged inter-stimulus periods over 30 min, this effect could not be caused by the anaesthesia itself.

Conclusions: Selective vagal nerve stimulation not only lowers the blood pressure during the actual phase of stimulation in rats, but the blood pressure also stays below its initial value during inter-stimulus periods. Intermitting selective vagal nerve stimulation might therefore hold the key to an energy-efficient non-medical antihypertensive treatment in future.