Tonotopic changes in 2-deoxyglucose activity in chick cochlear nucleus during hair cell loss and regeneration

Following cochlear ablation, auditory neurons in the central nervous system (CNS) undergo alterations in morphology and function, including neuronal c ell death. The trigger for these CNS changes is the abrupt cessation of eig hth nerve fiber activity. Gentamicin can cause ototoxic damage to cochlear hair cells responsible for high frequency hearing. In birds, these hair cel ls can regenerate. Therefore, gentamicin causes a partial, yet reversible i nsult to the ear. It is not known how this partial hair cell damage affects excitatory input to the cochlear nucleus. We examined chick cochlear nucle us activity during hair cell loss and regeneration by measuring 2-deoxygluc ose (2DG) uptake. Normal animals showed a rostral to caudal gradient of 2DG activity, with higher activity in caudal regions. When hair cells are dama ged (2, 5 days), 2DG uptake is decreased in cochlear nucleus. When hair cel ls regenerate (9, 16, 28 days), 2DG uptake returns to control levels. This decrease and subsequent return of activity only occurs in the rostral, high frequency region of the cochlear nucleus. No changes are seen in the cauda l, low frequency region. These results suggest that changes in activity of cochlear nucleus occur at a similar time course to anatomical changes in th e cochlea. (C) 1999 Elsevier Science B.V. All rights reserved.