Abstract:
Extracochlear electrical stimulation seems to induce relaxation with temporal tinnitus relief in patients. Electrical treatment was accompanied by increased cutaneous blood flow in the digits, although there was no clear tendency among tinnitus suppression, relaxation, and blood flow. To elucidate the effect on the autonomic system in the experimental animals, the blood pressure, the heart rate, and sympathetic and parasympathetic nervous activities were examined in rats and rabbits. Various stimuli such as square pulses, biphasic pulses, or sine waves were given to the cochlea with the electrodes on the round windows. The arterial blood pressures decreased in most cases in rabbits, while they decreased, increased, or represented biphasic changes in rats depending upon the type of stimulation. The autonomic activity seemed to follow the drifts in blood pressure, but the results did not show which autonomic system contributed to the drifts clearly. The effect of electrical stimulation on the autonomic nervous system was quantitatively analyzed and the effects of the stimulus waveforms and frequencies on the autonomic reactions were compared. One would look for the stimulating conditions suitable for tinnitus suppression or hearing improvement without the presumed side effects of stimulation.