Quinine-induced Hearing Loss in the Guinea Pig is Not Affected by the Ca²⁺ Channel Antagonist Verapamil

Abstract

It is well documented that quinine induces reversible hearing loss and tinnitus. The purpose in this study was to induce a quinine hearing loss and to investigate if verapamil, a Ca²⁺ channel antagonist of L-type might affect the response. Pigmented guinea pigs (n = 24) were anaesthetized by atropine, Hypnorm and midazolam but permitting spontaneous respiration. An electrode of platinum was placed on the round window and short (10 msec) tone pulses at 8 kHz were presented to the external ear. A typical deflection of the N₁ -wave was determined as the hearing threshold. Quinine hydrochloride 40 mg/kg and verapamil lmg/kg were given intravenously. Quinine induced a significant and reversible hearing loss (mean 16 dB). This hearing loss was not at all affected by verapamil given before or after quinine. Verapamil often caused acute cardiac arrest and particularly the combination verapamil followed by quinine-induced death to the animal. We conclude that verapamil and quinine had no in vivo interaction with regard to the hearing ability.

Key Words:

• Ca²⁺ channel antagonist
• hearing loss
• quinine
• tinnitus