Elsevier

Neuroscience

Volume 154, Issue 1, 12 June 2008, Pages 315-328
Neuroscience

The changing auditory system: Development, learning, aging and disease
Inhibitory synaptogenesis in the rat anteroventral cochlear nucleus

https://doi.org/10.1016/j.neuroscience.2008.03.027Get rights and content

Abstract

Spherical cells in the anteroventral division of the cochlear nucleus, which relay excitatory inputs from the auditory nerve, also receive both GABAergic and glycinergic inhibitory synapses. Inhibition mediated by GABA and glycine fulfils essential roles in the processing abilities of these and other auditory neurons. However, the developmental program leading to a mature complement of GABAergic and glycinergic synapses and microcircuits is largely unknown. Because of their relatively simple geometry, spherical cells provide an excellent model for unraveling basic developmental patterns of inhibitory synaptogenesis. Using a combination of high resolution immunocytochemical methods, we report that, in the rat, synapses containing GABA or glycine are deployed on spherical cell bodies over a time period extending well beyond hearing onset. Such postnatal developmental recruitment of inhibitory endings is progressive, although there are two distinct leaps in their numbers. The first occurs by the end of the first postnatal week, prior to hearing onset, and the second, during the third postnatal week, after hearing onset. This pattern suggests that adjustments in inhibition could be driven by acoustic experience. While GABAergic and glycinergic endings are maturing and growing in number and size, their neurotransmitter content also appears to be developmentally regulated. Quantitative ultrastructural immunocytochemistry with colloidal gold suggests that GABA and glycine accumulation in synaptic endings follows a staggered pattern, with labeling stabilizing at adult levels by postnatal day 21. This may account for adjustments in synaptic efficacy and strength.

Section snippets

Preparation of animals and tissue

Thirty-three male Wistar rats from postnatal day (P) 0 to adulthood (P90) were used. Their care and handling were approved and supervised by institutional animal care and use committees, following national and European Union regulations on the matter. Every effort was made to minimize the number of animals used and their suffering.

For each developmental age, animals came from different litters and were grouped as follows: day of birth=P0 (n=3), P3 (n=3); P5 (n=3), P7 (n=3), P10 (n=3), P12 (n

Adult AVCN

As previously reported (Kolston et al 1992, Juiz et al 1996) numerous GABA and/or glycine immunoreactive puncta and fibers were seen in this CN division (Fig. 1). Both with postembedding immunoperoxidase (Fig. 1A–B) and immunofluorescence (Fig. 1C–E), punctate labeling was particularly dense around unlabeled spherical cell bodies identifiable in rostral portions of the AVCN, where our observations were focused. Puncta and fibers co-labeled for both inhibitory amino acids were abundant (Fig. 1A,

Discussion

Using a combination of high resolution immunocytochemical methods at the light and electron microscopic levels we have followed the postnatal structural development of GABAergic and glycinergic synapses in the AVCN. The emerging picture is that of a protracted postnatal period of structural and neurochemical development of inhibitory synapses in the rat AVCN extending well beyond hearing onset. This may represent a structural background for experience driven adjustments in inhibition, which may

Acknowledgments

The authors are grateful to Mrs. Adelaida Baso for excellent technical assistance and Mr. Stuart Ingham for photographic assistance. Dr. Mari Luz Campos provided expertise in confocal microscopy, through the core facility (SS. TT. II.) of the Universidad Miguel Hernández. Prof. Peter Somogyi and Dr. R. J. Wenthold kindly provided antibodies against GABA and glycine, respectively. Work supported by Ministerio de Ciencia y Tecnología (BFI2003-09147-C02-02 and BFU 2006-13974) to J.M.J.; Ministerio

References (62)

  • K. Sato et al.

    Expression of glycine receptor subunits in the cochlear nucleus and superior olivary complex using non-radioactive in-situ hybridization

    Hear Res

    (1995)
  • K. Sato et al.

    Expression of glycine receptor subunit mRNAs in the rat cochlear nucleus

    Hear Res

    (2000)
  • L. Schweitzer et al.

    Development of GAD-immunoreactivity in the dorsal cochlear nucleus of the hamster and cat: light and electron microscopic observations

    Hear Res

    (1993)
  • L.P. Tolbert et al.

    The neuronal architecture of the anteroventral cochlear nucleus of the cat in the region of the cochlear nerve root: Electron microscopy

    Neuroscience

    (1982)
  • C. Vale et al.

    Expression and developmental regulation of the K+-Cl cotransporter KCC2 in the cochlear nucleus

    Hear Res

    (2005)
  • R.J. Wenthold et al.

    Glycine immunoreactivity localized in the cochlear nucleus and superior olivary complex

    Neuroscience

    (1987)
  • R.A. Altschuler et al.

    Inhibitory amino acid synapse and pathways in the ventral cochlear nucleus

  • A. Angulo et al.

    Morphology of the rat cochlear primary afferents during prenatal development: a Cajal's reduced silver and rapid Golgi study

    J Anat

    (1987)
  • G.B. Awatramani et al.

    Staggered development of GABAergic and glycinergic transmission in the MNTB

    J Neurophysiol

    (2005)
  • Y. Ben-Ari et al.

    GABA: A pioneer transmitter that excites immature neurons and generates primitive oscillations

    Physiol Rev

    (2007)
  • C.G. Benson et al.

    Retrograde transport of [3H]glycine from the cochlear nucleus to the superior olive in the guinea pig

    J Comp Neurol

    (1990)
  • P. Blaesse et al.

    Oligomerization of KCC2 correlates with development of inhibitory neurotransmission

    J Neurosci

    (2006)
  • S. Brenowitz et al.

    Maturation of synaptic transmission at end-bulb synapses of the cochlear nucleus

    J Neurosci

    (2001)
  • J.K. Brunso-Bechtold et al.

    Ultrastructural development of the medial superior olive (MSO) in the ferret

    J Comp Neurol

    (1992)
  • N.B. Cant

    Structural development of the mammalian auditory pathways

  • D.M. Caspary et al.

    Inhibitory inputs modulate discharge rate within frequency receptive fields of anteroventral cochlear nucleus neurons

    J Neurophysiol

    (1994)
  • R.A. Code et al.

    Development of GABA immunoreactivity in brainstem auditory nuclei of the chick: ontogeny of gradients in terminal staining

    J Comp Neurol

    (1989)
  • E. Friauf

    Developmental changes and cellular plasticity in the superior olivary complex

  • E. Friauf et al.

    Development of adult-type inhibitory glycine receptors in the central auditory system of rats

    J Comp Neurol

    (1997)
  • X.B. Gao et al.

    GABA release from mouse axonal growth cones

    J Physiol

    (2000)
  • O. Gleich et al.

    Postnatal development of GABA- and glycine-like immunoreactivity in the cochlear nucleus of the Mongolian gerbil (Meriones unguiculatus)

    Cell Tissue Res

    (1998)
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    Present address: Complejo Hospitalario Universitario de Albacete, Unidad de Investigación, C/Hermanos Falcó No. 37, E-02006, Albacete, Spain.

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