Abstract
Endolymphatic hydrops was produced in guinea pigs, and the inner ear microvasculature was observed morphologically. Then inner ear circulatory disturbance was induced by noise exposure in ears with endolymphatic hydrops and the changes were observed morphologically. Glycerol was administered to the animals before and after noise exposure and the differences were compared.
1) Examination of the inner ear vessels by the casting method revealed slight vasoconstriction-like changes in the vessels of the cochlear lateral wall and narrowing in the capillary of the saccular macula, which suggested the presence of slight inner ear circulatory disturbance.
2) In ears with endolymphatic hydrops exposed to noise, blood cell sludge was observed around the upper turn of the cochlea from the upper coiled arteriole to the capillary of the stria vascularis under light and electron microscopy by the cracking method. Observation by the casting method also revealed the vasoconstriction-like changes of the capillary of the stria vascularis around the upper turn of the cochlea. Even when the frequency of the noise applied was changed, similar inner ear circulatory disturbances occurred around the upper turn of the cochlea, which suggests that this region is the site most liable to injury in ears with endolymphatic hydrops.
3) When glycerol was administered to ears with endolymphatic hydrops under noise exposure, distension of Reissner's membrane was decreased, blood cell sludge was diminished and vasoconstriction-like changes of the capillary of the stria vascularis were not observed. Compared to ears with endolymphatic hydrops under noise exposure without glycerol administration, the severity of hydrops and the circulatory disturbance were clearly reduced. These results suggest that improvement of the inner ear circulatory disturbance as well as the osmotic force of glycerol are involved in the relief of endolymphatic hydrops.
