Stimulation of the sympathetic zones of the hypothalamus produced increase in the oxygen tension in the inner ear and it is seemed to be due to increase in blood pressure during stimulation. However the animals showed increase in the oxygen tension during stimulation of the parasympathetic zones, followed by decrease in it, although stimulation did not produce any increase in blood pressure.
This paradoxical phenomenon was seemed to have been resolved by the study on permeability of the cochlea. Large amounts of trypan blue were injected intravenously to the animals during stimulation of the hypothalamus. Then the cochlea was examined under biocular microscope, revealing blue stain of the basilar membrane in all the animals in which the sympathetic or parasympathetic zones were stimulated. Probably increase in the oxygen tension during the stimulation of the hypothalamus would partially be due to increase in permeability of the basilar membrane.
The cochlear microphonics was not revealed to be influenced by stimulation of any areas of the hypothalamus. The histological features of the cochlea after stimulation remained unchanged.
