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Exp Brain Res (2009) 195:241260 DOI 10.1007/s00221-009-1776-7
RESEARCH ARTICLE
Neuronal subtype identity in the rat auditory brainstem as deWned by molecular proWle and axonal projection
Michaela Fredrich Adrian Reisch Robert-Benjamin Illing
Received: 2 January 2009 / Accepted: 13 March 2009 / Published online: 2 April 2009 Springer-Verlag 2009
Abstract The nuclei of the auditory brainstem harbor a diversity of neuronal cell types and are interconnected by excitatory as well as inhibitory ascending, descending, and commissural pathways. Classically, neurons have been characterized by size and shape of their cell body and by the geometry of their dendrites. Our study is based on the use of axonal tracers in combination with immunocyto-chemistry to identify and distinguish neuronal subtypes by their molecular signature in dorsal and ventral cochlear nucleus, lateral superior olive, medial superior olive, medial nucleus of the trapezoid body, and inferior colliculus of the adult rat. The presumed neurotransmitters glutamate, glycine, and GABA were used alongside the calcium-binding proteins parvalbumin, calretinin, and calbindin-D28k as molecular markers. Our data provide distinct extensions to previous characterizations of neuronal sub-types and reveal regularities and diVerences across auditory brainstem nuclei that are discussed for their functional implications.
Keywords Amino acid neurotransmitters
Calcium-binding proteins Cochlear nucleus
Inferior colliculus Molecular signature Superior olive
Abbreviations
AVCN Anteroventral cochlear nucleusBDA Biotinylated dextrane amineCaBPs Calcium-binding proteinsCB CalbindinCIC Central nucleus of the inferior colliculus CNC Cochlear nuclear complexCR CalretininDCN Dorsal cochlear nucleusDNLL Dorsal nucleus of the lateral lemniscus. EPTA Ethanolic phosphotungstic acidGABA Gamma amino butyric acidGlu GlutamateGly GlycineLOC Lateral olivocochlear neuronsLSO Lateral superior oliveMNTB Medial nucleus of the trapezoid body MSO Medial superior olivePV ParvalbuminPVCN Posteroventral cochlear nucleusSOC Superior olivary complexVCN Ventral cochlear nucleus
Introduction
The central auditory system of the mammalian brain serves spectral and temporal analysis of, and feature detection in, the acoustic environment. These fundamental sensory functions are made possible by the interaction of speciWc types of neurons arrayed in various brainstem nuclei and fore-brain structures connected by an intricate network of ascending, descending, and commissural pathways.
Until fairly recently, the quest for neuronal subtype identity was based on Nissl staining (Osen 1969), Golgi
M. Fredrich A. Reisch R.-B. Illing (&)
Neurobiological Research Laboratory,
Department of Otorhinolaryngology, University of Freiburg, Killianst. 5, 79106 Freiburg, Germanye-mail: [email protected]
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