Plastic changes in glycine and GABA release and uptake in adult brain stem auditory nuclei after unilateral middle ear ossicle removal and cochlear ablation

Exp Neurol. 1998 Jun;151(2):273-88. doi: 10.1006/exnr.1998.6812.

Abstract

[i] In young adult guinea pigs, the effects of unilateral ossicle removal and unilateral cochlear ablation were determined on [14C]glycine or [14C]GABA release and uptake measured in subdivisions of the cochlear nucleus (CN), the superior olivary complex, and the auditory midbrain, after 2 or 5, 59, and 145 postlesion days. Activities were compared to those of age-matched, unlesioned controls. [ii] [14C]Glycine release declined bilaterally in the anteroventral and dorsal CN after ossicle removal and in the dorsal CN after cochlear ablation. [iii] Transient elevations of release occurred at 59 days in the ipsilateral posteroventral CN ([14C]glycine) and bilaterally in the ventral nucleus of the lateral lemniscus ([14C]GABA) after ossicle removal, and bilaterally in the medial superior olive ([14C]glycine) after cochlear ablation. [iv] In the medial nucleus of the trapezoid body, [14C]GABA release was depressed bilaterally 5 days after ossicle removal, but was elevated at 145 days contralaterally after ossicle removal and ipsilaterally after cochlear ablation. [v] In the contralateral central nucleus of the inferior colliculus, [14C]GABA release was elevated persistently after ossicle removal. After cochlear ablation, release was elevated at 5 days, near the control at 59 days, and elevated again at 145 days. [vi] After both lesions, [14C]glycine uptake was elevated bilaterally in the CN and medial superior olive. [14C]GABA uptake became depressed by 59 or 145 days bilaterally in the auditory midbrain. [vii] These changes may stem from regulation and may contribute to mechanisms that generate symptoms such as loudness recruitment and tinnitus, which often accompany hearing loss.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Age Factors
  • Animals
  • Auditory Pathways / metabolism
  • Carbon Radioisotopes
  • Cochlea / surgery*
  • Cochlear Nerve / metabolism
  • Cochlear Nucleus / metabolism*
  • Denervation
  • Ear Ossicles / surgery*
  • Female
  • Glycine / pharmacokinetics*
  • Guinea Pigs
  • Male
  • Nerve Degeneration / pathology
  • Nerve Fibers / pathology
  • Neuronal Plasticity / physiology
  • gamma-Aminobutyric Acid / pharmacokinetics*

Substances

  • Carbon Radioisotopes
  • gamma-Aminobutyric Acid
  • Glycine