Modeling of Signal Transmissions in Nerves in Vitro for the Development of a Renal Nerve Cooling Device for Hypertension Control

Hyperactivity of the central nervous system may increase feedback gains in the hemodynamic system. We have been developing a totally implantable renal nerve cooling system which is capable of changing the hyperactive renal nerve function; in particular, those that reversibly eliminate excess signal-gains by using Peltier effects. In this study, we examined the effect of cooling on neurotransmission in vivo and in vitro. Then we evaluated functional characteristics of signal transmission by the change in thermal implication on the nerve to perform thermal sedation of nervous activity. After the animal experimental procedures, we examined the electrical signal transmission in the nerves extracted from the goats. Using the neurogram amplifier and the functional signal generator, we tested the signal transmission characteristics through the nerves and evaluated their filtering functions by regional nerve cooling. In order to examine of natural renal neurotransmission, the renal nerves were dissected from the left kidney in goats under the normal anesthesia using 2.5% of isoflurane. Aortic pressure and the neurogram were measured, and we applied the low-temperature exposure of the nerve. The electric signals exhibited filtered-transmission through the nerve by the cooling in vitro. In the goat’s experiment, the amplitude of the signal which was obtained at the renal nerve decreased when we decreased the nerve surface temperature by -15 degrees. Then we could evaluate these transmission functions of the renal nerve with the interactive changes of the temperature which was to be controlled by the cooling device. We examined characteristics of the signal transmission in the renal nerve in goats by cooling. And we could evaluate these changes in the functional transmission model with the thermal interactions.