AFFERENT REGULATION OF GLYCINE RECEPTOR DISTRIBUTION IN THE GERBIL LSO

Synaptic activity plays an important role in many aspects of neuronal development, particularly the expression of proteins. In this study, t he influence of inhibitory and excitatory afferents on the development of glycine receptor density in the lateral superior olive (LSO) of Mo ngolian gerbils was investigated. Afferent activity was manipulated by removing one or both cochleas at postnatal day 7, prior to the onset of sound-evoked responses. Due to the anatomy of the LSO, these manipu lations result in either excitatory denervation, inhibitory denervatio n, or both. The density of glycine receptors in the LSO was determined at 21 days postnatal. Glycine receptors were either labeled with trit iated strychnine (H-3-SN) or with an antibody directed against gephyri n, a protein closely associated with the receptor complex. Antibody bi nding was used to quantify the differential glycine receptor density b etween the medial limb (high frequency area) and the lateral limb (low frequency area) of the LSO. H-3-SN was used to quantify the amount of glycine receptors in each part of the LSO in control and experimental animals. In addition, changes in neuron density and neuron cross-sect ional area were quantified following cochlear ablations. In control an imals, the amount of glycine receptors is about 2- to 3-fold higher in the high-frequency than in the low-frequency region. In bilaterally a blated animals, the same density of glycine receptors was measured in the high-and low-frequency region. Unilateral ablations had no signifi cant effect on glycine receptor distribution, either ipsi-or contralat eral to the ablation. The neuron cross-sectional area decreased about 30% in the ipsilateral LSO of unilaterally ablated animals and in bila terally ablated animals. However, alterations of soma density and cros s-sectional area were similar in the high-and low-frequency projection region. These results suggest that the distribution of glycine recept ors is only changed when excitatory and inhibitory afferents have been denervated. (C) 1998 Wiley-Liss, Inc.