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Auditory and Vestibular Systems

開催日 2014/9/12
時間 14:00 - 15:00
会場 Poster / Exhibition(Event Hall B)

Auditory-evoked responses of large GABAergic neurons in the inferior colliculus

  • P2-152
  • 伊藤 哲史 / Tetsufumi Ito:1 
  • 1:福井大学・医・人体解剖学・神経科学 / Dept of Anat, Faculty of Med Sci, Univ of Fukui 

The inferior colliculus (IC) receives ascending inputs from virtually all auditory nuclei, and is considered to be the first integration center in the auditory system. However, the local circuitry which underlie the integration of auditory information has remained unclear. Large GABAergic (LG) neurons in the IC receive converged excitatory inputs from lower brainstem nuclei and local sources. In the central nucleus of the IC, LG neurons are suggested to be stellate cells, that extend their dendrites to neighboring isofrequency laminae. If so, LG neurons may integrate spectral information. In this study, we employed juxtacellular staining method to relate neuronal cell types and their auditory-evoked responses in rat IC. After recording of auditory-evoked single units, tertramethylrhodamine-cadaverine was iontophoretically injected into recorded neurons. After a survival period, animals were perfused with fixative, and fixed brains were dissected out, cryoprotected, and sectioned. Cell types of labeled neurons were identified by immunohistochemistry for GAD67 and VGLUT1/2. Serial brain sections were further immunostained for tetramethylrhodamine to reconstruct dendritic and axonal morphology of labeled neurons. As a result, LG neurons in the ICC were found to be stellate cells, and broadly tuned for tone frequency. They showed strong response to broadband noise and FM sweep as well as tone burst of characteristic frequency. In some cases, we successfully labeled both local and projecting axons of LG cells. Projecting axons were found in the brachium of the IC, commissure of the IC, and lateral lemniscus. These results suggest that LG neurons integrate spectral information and transmit the information to variety of auditory nuclei.

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