A study regarding sensorineural hearing impairment with morphological changes in stria vascularis induced by the administration of Arg-Vasopressin

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Wistar rats were intraperitoneally injected 0.02 units/g of AVP (Pitressin; Arg-vasopressin. Daiichi-Sankyo, Japan)in the all experiments in this study. ABR thresholds gradually increased significantly upto 60 min after the injection. When the dehydration load pretreatment for 24h was added, ABR thresholds rapidly increased significantly up to 10 min after the injection. However, the morphological endolymphatic hydrops in cochlea was not detected under a light microscopy. However, the enlargement of an area lacking intracellular organelles in the intermediate cells in stria vascularis or a so called “vacuole” was detected under transmission electron microscopy after the AVP injection. When the dehydration load pretreatment for 24h was added, the vacuole area increased with AVP injection. However, when the V2Rantagonist (OPC-31260, donated by Otsuka Pharmaceutical) was administered before AVP,vacuole formation was suppressed significantly. Conversely, vacuole formation was not suppressed when the V1aR antagonist (OPC-21268, donated by Otsuka Pharmaceutical) was administered before AVP injection.