Effect of dexmedetomidine on noise-induced hearing loss in guinea pigs

Abstract

Objective To evaluate the effect of dexmedetomidine on noise-induced hearing loss in guinea pigs.Methods Twenty-four adult male guinea pigs,aged 3 months,weighing 400-500 g,were randomly divided into 3 groups (n =8 each) using a random number table:dexmedetomdine group (group D),noise-induced hearing loss group (group N) and dexmedetomidine + noise-induced hearing loss group (group DN).A loading dose of dexmedetomidine 5 μg/kg was infused over 5 min,followed by 135 min of infusion at a rate of 10 μg· kg-1 · h-1.The equal volume of normal saline was infused in group N.Groups N and DN were exposed to noise of 4 kHz center frequency and 118-122 dB SPL for 120 min starting from 20 min of administration.Mean arterial pressure (MAP) and cochlear blood flow (COBF) were recorded before administration and every 5 min during drug administration.The changing rate of COBF was calculated.Arterial blood samples were collected for determination of plasma concentration of noradrenaline (NE) by high performance liquid chromatography at 20 and 140 min of administration.Auditory brainstem response (ABR) threshold was recorded before administration and at 1 and 72 h and 10 days after the end of administration.Results Compared with group N,MAP was significantly decreased,the changing rate of COBF was increased at 5-10 min and 30-140 min of administration,ABR threshold was decreased at 1 and 72 h and 10 days after the end of administration,and the plasma concentration of NE was decreased at 140 min of administration in D + N group (P ＜ 0.05).Conclusion Dexmedetomidine can attenuate noise-induced hearing loss in guinea pigs possibly through inhibiting activation of sympathetic nerves and increasing COBF. Key words: Dexmedetomidine ; Hearing loss, noise-induced