Time course changes of vasopressin-induced enlargement of the rat intrastrial space and the effects of a vasopressin type 2 antagonist.
CONCLUSIONS
The intrastrial space was enlarged remarkably at 20 min after vasopressin (VP) injection, and this enlargement of the intrastrial space was reduced by administration of OPC-31260 before VP injection. These results suggest that VP increases the influx of water from the perlymph to the basal cells via aquaporin (AQP) 2 and causes the formation of endolymphatic hydrops.


OBJECTIVE
To investigate a time course of changes of the stria vascularis after VP injection and the influence of OPC-31260 on experimentally induced enlargement of the intrastrial space caused by VP injection.


METHODS
In the time course study, Wistar rats were injected with 50 microg/kg of VP subcutaneously. The stria vascularis specimens were harvested at 10, 20, 30, and 60 min after VP injection. For OPC-31260 administration, animals were administered 100 mg/kg of OPC-31260 orally 1 h before receiving 50 microg/kg of VP subcutaneously. The specimens were harvested 20 min after VP injection. These specimens were observed using transmission electron microscopy.


RESULTS
In the time course study, the incidence of intrastrial space enlargement was 50%, 100%, 25%, and 0% for 10, 20, 30, and 60 min, respectively. In the study with OPC-31260 administration, the stria vascularis showed no morphological changes.
Nishimura
Masahiko
M
Department of Otolaryngology, Kochi Medical School, Kohasu, Oko-cho, Nankoku, Kochi 783-8505, Japan. jm-nishimuram@kochi-u.ac.jp
Kakigi
Akinobu
A
Takeda
Taizo
T
Okada
Teruhiko
T
Doi
Katsumi
K
D000284:Administration, Oral; D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D051399:Aquaporin 2 / Q000037:antagonists & inhibitors; D001127:Arginine Vasopressin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001552:Benzazepines / Q000494:pharmacology*; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D018159:Endolymphatic Hydrops / Q000139:chemically induced* / Q000473:pathology*; D007279:Injections, Subcutaneous; D008575:Meniere Disease / Q000139:chemically induced / Q000473:pathology; D046529:Microscopy, Electron, Transmission; D011292:Premedication; D051381:Rats; D013316:Stria Vascularis / Q000187:drug effects* / Q000473:pathology*
D065092:Antidiuretic Hormone Receptor Antagonists; C496025:Aqp2 protein, rat; D051399:Aquaporin 2; D001552:Benzazepines; D001127:Arginine Vasopressin; C076251:mozavaptan