The changing auditory system: Development, learning, aging and diseaseEffects of cochlear ablation on amino acid concentrations in the chinchilla posteroventral cochlear nucleus, as compared to rat
Section snippets
Experimental procedures
Most of the procedures used in this study have been described previously (Godfrey and Matschinsky 1976, Ross et al 1995, Godfrey et al 2000, Godfrey et al 2005).
Effects of cochlear ablation on PVCN structural parameters
The volume of the PVCN on the lesioned side appeared to decrease by 84 days after unilateral cochlear ablation (Table 1). Because of the small numbers of measurements (one per cochlear nucleus) and sizable variation in PVCN volume even among sham animals, analysis of variance indicated no significant differences among the groups, even though the average at 84 days was significantly different from the sham average by t-test (P=0.002). The consistency of the volume reduction at 84 days for the
Considerations in interpreting the results
Although the most prominent changes in amino acid concentrations should be closely associated with the degeneration of auditory nerve fibers, the spatial resolution of the microchemical approach as applied here does not enable determination of which other neurons or glia may also be the sites of changes. However, previous measurements have suggested that concentrations of aspartate, glutamate, and serine are at least twice as high in neurons and GABA more than 10 times as high; glutamine and
Conclusions
Our results indicate that the slowness of the decreases of glutamate and aspartate concentrations in the chinchilla PVCN after carboplatin treatment relates partially to a slower loss of these amino acids from the central terminal regions of auditory nerve fibers during their degeneration in chinchillas than in rats or guinea pigs and partially to slower deterioration of the central terminal regions of auditory nerve fibers after carboplatin treatment than after cochlear ablation.
Our findings
Acknowledgments
We are grateful to Brent Martin, D.V.M., and his staff of the Division of Laboratory Animal Medicine of the University of Toledo Health Science Campus for assistance and advice at various stages of this project. Support for this research was received from the American Tinnitus Association and the University of Toledo Foundation.
References (59)
- et al.
Age-related changes in GABAA receptor subunit composition and function in rat auditory system
Neuroscience
(1999) - et al.
Choline acetyltransferase, glutamate decarboxylase and tyrosine hydroxylase in the cochlea and cochlear nucleus of the guinea pig
Brain Res
(1976) - et al.
Amino acid concentrations in rat cochlear nucleus and superior olive
Hear Res
(2000) - et al.
Amino acid concentrations in chinchilla cochlear nucleus at different times after carboplatin treatment
Hear Res
(2005) Central transport and distribution of labelled glutamic and aspartic acids to the cochlear nucleus in cats: an autoradiographic study
Neuroscience
(1979)- et al.
Effects of carboplatin on amino acid chemistry in chinchilla cochlear nucleus
Hear Res
(2002) - et al.
Neuronal and transneuronal degeneration of auditory axons in the brainstem after cochlear lesions in the chinchilla: cochleotopic and non-cochleotopic patterns
Hear Res
(1997) - et al.
Metabolic compartmentation of glutamate and glutamine: morphological evidence obtained by quantitative immunocytochemistry in rat cerebellum
Neuroscience
(1992) - et al.
Regulation of D-aspartate release and uptake in adult brain stem auditory nuclei after unilateral middle ear ossicle removal and cochlear ablation
Exp Neurol
(1997) - et al.
Altered glycinergic synaptic activities in guinea pig brain stem auditory nuclei after unilateral cochlear ablation
Hear Res
(2000)
Projections of low spontaneous rate, high threshold auditory nerve fibers to the small cell cap of the cochlear nucleus in cats
Neuroscience
Connections between the cochlear nuclei in guinea pig
Hear Res
AMPA receptor binding in adult guinea pig brain stem auditory nuclei after unilateral cochlear ablation
Exp Neurol
Human brain plasticity: an emerging view of the multiple substrates and mechanisms that cause cortical changes and related sensory dysfunctions after injuries of sensory inputs from the body
Brain Res Brain Res Rev
Fiber degeneration following lesions in the posteroventral cochlear nucleus of the cat
Exp Neurol
Glutamic acid and aspartic acid in subdivisions of the cochlear nucleus after auditory nerve lesion
Brain Res
Glutaminase and aspartate aminotransferase decrease in the cochlear nucleus after lesion of the auditory nerve
Brain Res
Projections from octopus cells of the posteroventral cochlear nucleus to the ventral nucleus of the lateral lemniscus in cat and human
Auditory Neuroscience
Changes with aging in the levels of amino acids in rat CNS structural elements IGlutamate and related amino acids
Neurochem Res
Changes with aging in the levels of amino acids in rat CNS structural elements IITaurine and small neutral amino acids
Neurochem Res
The biochemical basis of neuropharmacology
Effect of impact trauma on neurotransmitter and nonneurotransmitter amino acids in rat spinal cord
J Neurochem
Calpain immunoreactivity and morphological damage in chinchilla inner ears after carboplatin
J Assoc Res Otolaryngol
Commissural and intrinsic connections of the vestibular nuclei in the rabbit: a retrograde labeling study
Exp Brain Res
GABA and its related enzymes in the lower auditory system of the guinea pig
J Neurochem
Approach to three-dimensional mapping of quantitative histochemical measurements applied to studies of the cochlear nucleus
J Histochem Cytochem
Single unit activity in the posteroventral cochlear nucleus of the cat
J Comp Neurol
Neurotransmitter microchemistry of the cochlear nucleus and superior olivary complex
Effects of cochlear ablation on amino acid concentrations in rat cochlear nucleus and superior olive
Assoc Res Otolaryngol Abstr 188
Cited by (9)
Amino acid and acetylcholine chemistry in the central auditory system of young, middle-aged and old rats
2017, Hearing ResearchCitation Excerpt :However, the average thickness of the AudCtx was measured in several sections of each rat as the distance from its surface to the underlying external capsule. Free amino acid concentrations were measured by an HPLC assay (Hill et al., 1979; Ross et al., 1995; Godfrey et al., 2000, 2008, 2012, 2014, 2015). To each sample tube and some empty blank tubes were added 16 μL of 50% (vol/vol) methanol, containing an internal standard amino acid not present in the tissue (β-[2-thienly]-DL-serine) to correct for variations in injection volume.
Volumes of cochlear nucleus regions in rodents
2016, Hearing ResearchCochlear ablation effects on amino acid levels in the chinchilla cochlear nucleus
2015, NeuroscienceCitation Excerpt :The procedures used in this study were the same as used in our report on the chinchilla PVCN (Godfrey et al., 2008) and have been described previously (Godfrey and Matschinsky, 1976; Godfrey et al., 1977, 2000, 2008, 2014; Ross et al., 1995). The results are from the same chinchillas as used in our previous report on the PVCN (Godfrey et al., 2008). Eighteen adult chinchillas, one female and 17 male, obtained from Jarr Chinchilla, Hubbard, Ohio, USA, were divided into several cochlear-ablated and sham-lesioned groups (Table 1).
Effects of cochlear ablation on amino acid levels in the rat cochlear nucleus and superior olive
2014, Hearing ResearchCitation Excerpt :A preliminary report of results from this study has been presented (Godfrey et al., 2004a). Some of the results for the PVCN were included in a previous publication (Godfrey et al., 2008a), but they are also included here for completeness. The results are compared to those obtained previously for the other eighth cranial nerve system, the vestibular nuclear complex and its vestibular nerve root, after removal of its inner ear input by vestibular ganglionectomy (Li et al., 1996; Godfrey et al., 2004b).
- 1
Present address: K. Chen, Hough Ear Institute, Oklahoma City, OK, USA; Y.-M. Jin, Department of Neurosciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.