Effect of topical application of nitroglycerin on cochlear blood flow.
OBJECTIVE
To investigate whether topical application of the vasodilator nitroglycerin would increase cochlear blood flow without adversely affecting inner ear function.


METHODS
The effect of topical application of nitroglycerin to the round window membrane on cochlear blood flow was measured in 33 guinea pigs with a laser Doppler flowmeter. Endocochlear potential, as an indicator of inner ear function, was recorded by a glass microelectrode inserted through the round window membrane in a second series of 27 guinea pigs. Blood pressure was also monitored in both experiments.


RESULTS
Low doses (0.0001 to 1 microgram) of nitroglycerin induced an increase in cochlear blood flow with no change in blood pressure. The cochlear blood flow was maximally increased by approximately 50%. A high dose (50 micrograms) of nitroglycerin induced a significant decrease in blood pressure but did not significantly affect endocochlear potential.


CONCLUSIONS
Topical application of nitroglycerin may be useful in increasing cochlear blood flow in various inner ear diseases.
Ito
A
A
Department of Otorhinolaryngology, Nagoya University School of Medicine, Japan.
Nakashima
T
T
Yanagita
N
N
D000818:Animals; D003051:Cochlea / Q000098:blood supply* / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D007758:Ear, Inner / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D017078:Laser-Doppler Flowmetry; D008297:Male; D005996:Nitroglycerin / Q000009:adverse effects* / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects*; D012405:Round Window, Ear / Q000187:drug effects*; D013997:Time Factors
D005996:Nitroglycerin