Cochlear blood flow during occlusion and reperfusion of the anterior inferior cerebellar artery--effect of topical application of dexamethasone to the round window.
CONCLUSIONS
Topical application of dexamethasone may support autoregulation of cochlear blood flow (CBF), although it had no direct effect on CBF.


OBJECTIVE
Although intratympanic steroid therapy for patients with inner ear disorders is common, the mechanism by which steroids exert their effect is unclear. We investigated the response of CBF to topical application of dexamethasone onto the round window.


METHODS
Two concentrations of dexamethasone (3.3 mg/ml and 33 mg/ml dexamethasone in 0.5 microl saline) were applied to the round windows of rats, and CBF responses were measured using a laser Doppler flowmeter. The effects on CBF of a 2 h occlusion of the anterior inferior cerebellar artery (AICA) and subsequent release of the clamp with or without previous dexamethasone application were investigated.


RESULTS
No significant change in CBF was observed after topical application of dexamethasone, and it did not affect the decrease in CBF caused by AICA occlusion. However, recovery of CBF after release of the AICA clamp was better in animals treated with dexamethasone than in those that did not receive dexamethasone.
Otake
Hironao
H
Department of Otorhinolaryngology, Nagoya University School of Medicine, Nagoya, Japan.
Yamamoto
Hiroshi
H
Teranishi
Masaaki
M
Sone
Michihiko
M
Nakashima
Tsutomu
T
D000287:Administration, Topical; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002531:Cerebellum / Q000098:blood supply*; D003051:Cochlea / Q000098:blood supply*; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006706:Homeostasis / Q000187:drug effects; D007511:Ischemia / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D015427:Reperfusion Injury / Q000503:physiopathology*; D012405:Round Window, Ear / Q000187:drug effects / Q000503:physiopathology
D000893:Anti-Inflammatory Agents; D003907:Dexamethasone