Glycine receptors in adult guinea pig brain stem auditory nuclei: Regulation after unilateral cochlear ablation

In young adult guinea pigs, the effects of unilateral cochlear ablation wer e determined on the specific binding of [H-3]strychnine measured in subdivi sions of the cochlear nucleus (CN), the superior olivary complex, and the a uditory midbrain, after 2, 7, 31, 60, and 147 postlesion days. Changes in b inding relative to that in age-matched controls were interpreted as altered activity and/or expression of synaptic glycine receptors. Postlesion bindi ng declined ipsilaterally in most of the ventral CN and in the lateral supe rior olive (LSO). Binding was modestly deficient in the ipsilateral dorsal CN and in the anterior part of the contralateral anteroventral CN. Binding was elevated in the contralateral LSO. Transient changes also occurred. Bin ding was elevated transiently, between 2 and 31 days, contralaterally in pa rts of the anteroventral CN, bilaterally in the medial superior olive (MSO) , and bilaterally in most of the midbrain nuclei. Binding was deficient tra nsiently, at 60 days, in most of the contralateral CN and bilaterally in th e midbrain nuclei. The present findings, together with previously reported postlesion changes in glycine release, were consistent with persistently we akened glycinergic inhibitory transmission ipsilaterally in the ventral CN and the LSO and bilaterally in the dorsal CN. Glycinergic inhibitory transm ission was strengthened in the contralateral LSO and transiently strengthen ed in the MSO bilaterally. A hypothetical model of the findings suggested t hat glycine receptor regulation may depend on excitatory and glycinergic in put to auditory neurons. The present changes in glycine receptor activity m ay contribute to altered auditory functions, which often accompany hearing loss. (C) 1998 Academic Press.