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Titolo:
Efferent axons in the avian auditory nerve
Autore:
Koppl, C;
Indirizzi:
Tech Univ Munich, D-85747 Garching, Germany Tech Univ Munich Garching Germany D-85747 ich, D-85747 Garching, Germany
Titolo Testata:
EUROPEAN JOURNAL OF NEUROSCIENCE
fascicolo: 10, volume: 13, anno: 2001,
pagine: 1889 - 1901
SICI:
0953-816X(200105)13:10<1889:EAITAA>2.0.ZU;2-J
Fonte:
ISI
Lingua:
ENG
Soggetto:
BASILAR PAPILLA; BARN OWL; ACETYLCHOLINESTERASE ACTIVITY; GALLUS-DOMESTICUS; BRAIN-STEM; INNER-EAR; COCHLEAR; CHICKEN; INNERVATION; MORPHOLOGY;
Keywords:
barn owl; basilar papilla; bird; chicken; cochlea; emu; hearing; starling;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
47
Recensione:
Indirizzi per estratti:
Indirizzo: Koppl, C Tech Univ Munich, Lichtenbergstr 4, D-85747 Garching, Germany Tech Univ Munich Lichtenbergstr 4 Garching Germany D-85747 rmany
Citazione:
C. Koppl, "Efferent axons in the avian auditory nerve", EUR J NEURO, 13(10), 2001, pp. 1889-1901

Abstract

The sensory hair cells of the inner ear receive both afferent and efferentinnervation. The efferent supply to the auditory organ has evolved in birds and mammals into a separate complex system, with several types of neuronsof largely unknown function. In this study, the efferent axons in four different species of birds (chicken, starling, barn owl and emu) were examinedanatomically. Total numbers of efferents supplying the cochlear duct (auditory basilar papilla and the vestibular lagenar macula) were determined; separate estimates of the efferents to the lagenar macula only were also derived and subtracted. The numbers for auditory efferents thus varied between 120 (chicken) and 1068 (barn owl). Considering the much larger numbers of hair cells in the basilar papilla, each efferent is predicted to branch extensively. However, pronounced species-specific differences as well as regional differences along the tonotopic gradient of the basilar papilla were documented. Myelinated and unmyelinated axons were found, with mean diameters of about 1 mum and about 0.5 mum, respectively. This suggests two basic populations of efferents, however, they did not appear to be distinguished sharply. Evidence is presented that some efferents lose their myelination at the transition from central oligodendrocyte to peripheral Schwann cell myelin. Finally, a comparison of the four bird species evaluated suggests that the efferent population with smaller, unmyelinated axons is the phylogenetically more primitive one. A new population probably arose in parallel with the evolution and differentiation of the specialized hair-cell type it innervates, the short hair cell.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 30/11/20 alle ore 12:41:33