Plastic changes in glycine and GABA release and uptake in adult brain stem auditory nuclei after unilateral middle ear ossicle removal and cochlear ablation.
[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.
Suneja
S K
SK
Department of Anatomy, University of Connecticut Health Center, Farmington, Connecticut, 06030, USA.
Potashner
S J
SJ
Benson
C G
CG
D000367:Age Factors; D000818:Animals; D001306:Auditory Pathways / Q000378:metabolism; D002250:Carbon Radioisotopes; D003051:Cochlea / Q000601:surgery*; D003056:Cochlear Nerve / Q000378:metabolism; D017626:Cochlear Nucleus / Q000378:metabolism*; D003714:Denervation; D004429:Ear Ossicles / Q000601:surgery*; D005260:Female; D005998:Glycine / Q000493:pharmacokinetics*; D006168:Guinea Pigs; D008297:Male; D009410:Nerve Degeneration / Q000473:pathology; D009412:Nerve Fibers / Q000473:pathology; D009473:Neuronal Plasticity / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000493:pharmacokinetics*
D002250:Carbon Radioisotopes; D005680:gamma-Aminobutyric Acid; D005998:Glycine