The effect of cochlear nerve lesion on the release of glutamate, aspartate, and GABA from cat cochlear nucleus, in vitro
Summary
Pool studies of glutamate and aspartate have suggested a transmitter role for these amino acids in cochlear nerve endings. As further evidence. the K+-evoked release of glutamate, aspartate and GABA was measured in cat cochlear nucleus slices in vitro and compared to the release following a cochlear nerve lesion. Using [3H]glutamine as precursor, the K+-evoked release of glutamate and γ-aminobutyric acid (GABA) was respectively 4.1 and 7.2 times the spontaneous release. Using [14C]glutamate as a marker, the K+-evoked release of glutamate and GABA was respectively 7.1 and 2.8 times the basal release. All K+-evoked releases were Ca++-dependent. Nine days after unilateral lesion of the cochlear nerve in the cat, the glutamate release decreased by about 75% on the lesioned side compared to the intact one, whereas the GABA release was not decreased. The labelled tissue glutamate, either synthesized from [3H]glutamine or labelled with [14C]glutamate, was also markedly decreased on the lesioned side. In comparison, the evoked release of aspartate, newly synthesized from [14C]glutamate, remained low and was only decreased by about 45% after cochlear nerve lesions. Comparing cat with rat cochlear nucleus, the glutamate release was similar in both animals, whereas the GABA release was much higher in the rat.
It is concluded that glutamate and to a lesser extent aspartate are likely to be released from cochlear nerve terminals, supporting a transmitter role in these nerve fibres for both amino acids.
Key words
Glutamate, aspartate, GABA In vitro release Cochlear nerve lesion Cochlear nucleusPreview
Unable to display preview. Download preview PDF.
References
- Besson M J, Chéramy A, Feltz P (1971) Dopamine: spontaneous and drug-induced release from the caudate nucleus in the cat. Brain Res 32: 407–424Google Scholar
- Bradford H F, Thomas A J (1969) Metabolism of glucose and glutamate by synaptosomes from mammalian cerebral cortex. J Neurochem. 16: 1495–1504Google Scholar
- Bradford H F, Ward H K (1976) On glutaminase activity in mammalian synaptosomes. Brain Res 110: 115–125Google Scholar
- Cheng S C, Mela P (1966) CO2 fixation in the nervous system — II Environmental effects on CO2 fixation in lobster nerve. J Neurochem 13: 281–287Google Scholar
- Cotman C W, Hamberger A (1977) Glutamate as a CNS neurotransmitter: properties of release, inactivation and biosynthesis. In: Fonnum F (ed) Amino acids as chemical transmitters. Plenum Press, New York, pp 379–412Google Scholar
- Curtis D R (1979) Problems in the evaluation of glutamate as a central nervous system transmitter. In: Filer L J, Garattini S, Kare M R, Reynolds W A, Wurtman R J (eds) Glutamic acid: Advances in biochemistry and physiology. Raven Press, New York, pp 163–175Google Scholar
- Emson P C, Lindvall O (1979) Distribution of putative neurotransmitters in the neocortex. Neuroscience 4: 9–11Google Scholar
- Gauchy C M, Iversen L L, Jessell T M (1977) The spontaneous and evoked release of newly synthesized [14C]GABA from rat cerebral cortex, in vitro. Brain Res 138: 374–379Google Scholar
- Geffen L B, Jessel T M, Cuello A C, Iversen L L (1976) Release of dopamine from dendrites in rat substantia nigra. Nature 260: 258–260Google Scholar
- Johnson J L (1978) The excitant amino acids glutamic and aspartic acid as transmitter candidates in the vertebrate central nervous system. Prog Neurobiol 10: 155–202Google Scholar
- Kim J S, Hassler R, Haug P, Paik K S (1977) Effect of frontal cortex ablation on striatal glutamic acid level in rat. Brain Res 132: 377–378Google Scholar
- Lang W, Kubik S (1979) Primary vestibular afferent projections to the ipsilateral abducens nucleus in cats. Exp Brain Res 37: 177–181Google Scholar
- Reubi J C, Cuénod M (1979) Glutamate release in vitro from cortico striatal terminals. Brain Res 176: 185–188Google Scholar
- Reubi J C, Henke H, Fonnum F, Van den Berg C, Cuénod M (1978a) Glutamate as transmitter in the pigeon optic tectum. In: Abstracts Intern. Symp. on Development and Chemical Specificity of Neurons, p 62Google Scholar
- Reubi J C, Van den Berg C, Cuénod M (1978b) Glutamine as precursor for the GABA and glutamate transmitter pool. Neurosci Lett 10: 171–174Google Scholar
- Tapia, R, Gonzalez R M (1978) Glutamine and glutamate as precursors of the releasable pool of GABA in brain cortex clices. Neurosci Lett 10: 165–169Google Scholar
- Van den Berg C J, Garfinkel P (1971) A stimulation study of brain compartments: metabolism of glutamate and related substances in mouse brain. Biochem J 123: 211–218Google Scholar
- Weiler C T, Nyström B, Hamberger A (1979) Characteristics of glutamine vs. glutamate transport in isolated glia and synaptosomes. J Neurochem 32: 559–565Google Scholar
- Wenthold R J (1978) Glutamic acid and aspartic acid in subdivisions of the cochlear nucleus after auditory nerve lesion. Brain Res 143: 544–548Google Scholar
- Wenthold R J (1979) Release of endogenous glutamate, aspartate and GABA from cochlear nucleus slices. Brain Res 162: 338–343Google Scholar
- Wenthold R J, Morest D K (1976) Transmitter related enzymes in the guinea pig cochlear nucleus. Neurosci Abstr 2: 28–30Google Scholar
- Wenthold R J, Gulley R L (1977) Aspartic acid and glutamic acid levels in the cochlear nucleus after auditory nerve lesion. Brain Res 138: 111–123Google Scholar
- Wenthold R J, Gulley R L (1978) Glutamic acid and aspartic acid in the cochlear nucleus of the waltzing guinea pig. Brain Res 158: 279–284Google Scholar