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Titolo:
Myelinated dendrites in the mormyrid electrosensory lobe
Autore:
Meek, J; Hafmans, TGM; Han, V; Bell, CC; Grant, K;
Indirizzi:
Catholic Univ Nijmegen, Dept Anat & Embryol, NL-6500 HB Nijmegen, Netherlands Catholic Univ Nijmegen Nijmegen Netherlands NL-6500 HB egen, Netherlands Catholic Univ Nijmegen, Dept Biochem, NL-6500 HB Nijmegen, Netherlands Catholic Univ Nijmegen Nijmegen Netherlands NL-6500 HB egen, Netherlands Oregon Hlth Sci Univ, Inst Neurol Sci, Portland, OR 97209 USA Oregon Hlth Sci Univ Portland OR USA 97209 ol Sci, Portland, OR 97209 USA Unite Neurosci Integrat & Computationelles, F-91198 Gif Sur Yvette, FranceUnite Neurosci Integrat & Computationelles Gif Sur Yvette France F-91198
Titolo Testata:
JOURNAL OF COMPARATIVE NEUROLOGY
fascicolo: 3, volume: 431, anno: 2001,
pagine: 255 - 275
SICI:
0021-9967(20010312)431:3<255:MDITME>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Soggetto:
LATERAL-LINE LOBE; MORMYROMAST ELECTRORECEPTOR ORGANS; WEAKLY ELECTRIC FISH; GNATHONEMUS-PETERSII; SYNAPTIC PLASTICITY; CENTRAL CONNECTIONS; AFFERENT-FIBERS; GYMNOTIFORM FISH; PURKINJE-CELLS; IN-VITRO;
Keywords:
morphology; synaptology; ephapses; gamma-aminobutyric acid; presynaptic dendrite; teleost; weakly electric fish;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
57
Recensione:
Indirizzi per estratti:
Indirizzo: Meek, J Catholic Univ Nijmegen, Dept Anat & Embryol, POB 9101, NL-6500 HB Nijmegen, Netherlands Catholic Univ Nijmegen POB 9101 Nijmegen NetherlandsNL-6500 HB s
Citazione:
J. Meek et al., "Myelinated dendrites in the mormyrid electrosensory lobe", J COMP NEUR, 431(3), 2001, pp. 255-275

Abstract

This is the third paper in a series on the morphology, immunohistochemistry, and synaptology of the mormyrid electrosensory lateral line lobe (ELL). The ELL is a highly laminated, cerebellum-like structure in the rhombencephalon that subserves an active electric sense: Objects in the nearby environment are detected on the basis of changes in the reafferent electrosensory signals that are generated by the animal's own electric organ discharge. This paper concentrates on the intermediate (cell and fiber) layer of the medial zone of the ELL and pays particular attention to the large multipolar neurons of this layer (LMI cells). LMI cells are gamma -aminobutyric acid (GABA)ergic and have one axon and three to seven proximal dendrites that all become myelinated after their last proximal branching point. The axon projects to the contralateral homotopic region and has ipsilateral collaterals. Both ipsilaterally and contralaterally, it terminates in the deep and superficial granular layers. The myelinated dendrites end in the deep granular layer, where they most likely do not make postsynaptic specializations, but do make presynaptic specializations, similar to those of the LMI axons. Because it is not possible to distinguish between axonal and dendritic LMI terminals in the granular layer, the authors refer to both as LMI terminals. These are densely filled with small, flattened vesicles and form large appositions with ELL granular cell somata and dendrites with symmetric synaptic membrane specializations. LMI cells do not receive direct electrosensory input on their somata, but electrophysiological recordings suggest that they nevertheless respond strongly to electrosensory signals (Bell [1990] J. Neurophysiol. 63:303-318). Consequently, the authors speculate that the myelinated dendrites of LMI cells are excited ephaptically (i.e., by electric field effects) by granular cells, which, in turn, are excited via mixed synapses by mormyromast primary afferents. The authors suggest that this ephapticactivation of the GABAergic presynaptic terminals of the myelinated dendrites may trigger immediate synaptic release of GABA and, thus, may provide avery fast local feedback inhibition of the excited granular cells in the center of the electrosensory receptive field. Subsequent propagation of the dendritic excitation down the myelinated dendrites to the somata and axon hillocks of LMI cells probably generates somatic action potentials, resulting in the spread of inhibition through axonal terminals to a wide region around the receptive held center and in the contralateral ELL. Similar presynaptic myelinated dendrites that subserve feedback inhibition, until now, have not been described elsewhere in the brain of vertebrates. (C) 2001 Wiley-Liss, Inc.

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Documento generato il 27/09/20 alle ore 05:39:28