Monosynaptic connection between cochlear root neurons of the vestibulocochlear nerve and auricular motoneurons of the facial motor nucleus

THESES

Monosynaptic connection between cochlear root neurons of the vestibulocochlear nerve and auricular motoneurons of the facial motor nucleus (Abstract)^*. Thesis. São Paulo, 2004

José de Anchieta de Castro; Horta Jr

^{Correspondence}

Cochlear root neurons of the vestibulocochlear nerve (CRN) are involved in the acoustic startle reflex, which possesses a short-latency auricular component and is of great importance in the escape and survival of rodents. However, the pathway of the auricular component is not well understood.

To demonstrate a direct connection between CRN and auricular motoneurons in the rat, double-labeling experiment was performed using as neuronal tracers biotinylated dextran (anterograde) injected into the cochlear root and Fluoro-Gold® (retrograde) injected into the muscle levator auris longus. In addition, Fluoro-Gold® was injected into the medial subnucleus of the facial motor nucleus. At the structural level, overlappings between auricular motoneurons and axon terminals of the CRN were observed, which were confirmed at the ultrastructural level as asymmetric synapses containing round, small and electrolucent vesicles.

The direct connection between CRN and auricular motoneurons might represent the anatomical substrate of the fast auricular reflex after intense acoustic stimulation.

Key words: facial motor nucleus, cochlear root neurons, acoustic startle reflex; neuronal tracers, PINNA reflex, motoneurons

*

Conexão monossináptica entre os neurônios da raiz coclear do nervo vestíbulo-coclear e os motoneurônios auriculares do núcleo motor do nervo facial (Resumo). Tese de Doutorado, Universidade de São Paulo (Área: Anatomia). Orientador: Jackson Cioni Bittencourt; co-orientador: María Dolores Estilita López García. Financial Support: Ministerio de Ciencia y Tecnología - España (BFI2000-1358); F.S.E. (SA084/01) – España; FAPESP 00/06966-4 and FAPESP 01/13068-5

Publication Dates

• Publication in this collection
  25 Apr 2006
• Date of issue
  Dec 2004