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Effect of vasodilating agents on cochlear blood flow under loud sound exposure
A Okamoto1, T Tamura, M Hasegawa
1Department of Otorhinolaryngology, Tokyo Medical and Dental University, Japan.
Insights
This study investigated if a vasodilator drug could prevent loud noise-induced decreases in cochlear blood flow. While the drug did not fully block the drop, it maintained higher blood flow levels in guinea pigs.
Area of Science:
- Oto-rhino-laryngology
- Pharmacology
- Physiology
Background:
- Loud sound exposure is known to decrease cochlear blood flow.
- Understanding mechanisms to protect cochlear blood flow is crucial for preventing hearing loss.
Purpose of the Study:
- To investigate the effect of a vasodilating agent, dilazep dihydrochloride, on cochlear blood flow during loud sound exposure.
- To determine if dilazep can impede or prevent the sound-induced decline in cochlear blood flow.
Main Methods:
- Laser Doppler flowmetry was used to measure cochlear blood flow in guinea pigs.
- Animals were exposed to loud sound (120 dB SPL at 10 kHz) for 10 minutes.
- Dilazep dihydrochloride (5 mg/kg) was administered intravenously.
Main Results:
- Intravenous injection of dilazep dihydrochloride significantly increased baseline cochlear blood flow.
- Loud sound exposure caused a prompt decline in cochlear blood flow, which recovered upon cessation of the sound.
- During simultaneous loud sound exposure and dilazep administration, the drug did not fully prevent the blood flow decline but maintained levels higher than pre-injection baseline.
Conclusions:
- The vasodilating agent dilazep dihydrochloride partially mitigated the sound-induced reduction in cochlear blood flow.
- While not completely blocking the effect, dilazep demonstrated a protective capacity by maintaining elevated blood flow.
- These findings suggest potential therapeutic avenues for managing noise-induced cochlear dysfunction.
Abstract:
Loud sound has been proved by means of laser Doppler flowmetry to decline cochlear blood flow. The purpose of this study was to investigate the effect of a vasodilating agent on cochlear blood flow under loud sound exposure, i.e. whether the drug can impede blood flow decrease or not. As a vasodilating agent, dilazep dihydrochloride in a dose of 5 mg/kg was used. This drug caused a stable and significant increase of cochlear blood flow when intravenously injected into guinea pigs. When guinea pigs were exposed to loud sound (120 dB SPL at 10 kHz) for 10 min, cochlear blood flow promptly declined at the onset of sound stimulation and promptly recovered at its cessation. Then, dilazep dihydrochloride 5 mg/kg was injected intravenously into the same animal and loud sound (120 dB SPL at 10 kHz) was exposed for 10 min. Dilazep did not fully block a prompt decline of cochlear blood flow. However, the blood flow level was kept much higher than at pre-injection level. This study shows that a vasodilating agent which normally enhances blood flow probably does not completely block the sound-induced drop response in cochlear blood flow.