Effects of conductive hearing loss on gerbil central auditory system activity in silence

Animal models of conductive hearing loss (CHL) show altered structure and f unction in the central :auditory system (CAS), particularly following unila teral deprivation. Assessment of neuronal activity as measured by 7-deoxygl ucose (2-DG) uptake following CHL has been reported by two groups of invest igators, with different findings. Woolf and colleagues [Brain Res. 774 (198 3) 119] found that 2-DG uptake increased in the cochlear nucleus ipsilatera l to the CHL. while Tucci ct al. [Laryngoscope 109 (1999) 1359] found a dec rease in 2-DG uptake in the ipsilateral cochlear nucleus. One significant d ifference between the protocols in the two studies was that, in the first s tudy, animals were maintained in silence following 2-DG injection, whereas in the Tucci et al. study, animals were exposed to sound. The current study was designed to replicate the protocol used by Woolf ct al. Young adult ge rbils underwent unilateral malleus removal with bilateral canal ligation (n = 6) or a sham procedure (n = 7) 48 h prior to 2-DG administration and sac rifice. Optical density measurements were made from CAS nuclei. 2-DG uptake decreased in the ipsilateral cochlear nucleus and contralateral inferior c olliculus, and in nuclei of the superior olivary complex bilaterally, suppo rting the finding that CHL is associated with a decrease in CAS neuronal ac tivity. (C) 2001 Elsevier Science B.V. All rights reserved.