Calyx of Held

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The Calyx of Held is a particularly large synapse in the mammalian auditory central nervous system, so named by Hans Held in his 1893 article Die centrale Gehörleitung[1] because of its resemblance to the calyx of a flower.[2] Globular bushy cells in the anteroventral cochlear nucleus (AVCN)[3] send axons to the contralateral medial nucleus of the trapezoid body (MNTB), where they synapse via these calyces on MNTB principal cells.[4][5][6] These principal cells then project to the ipsilateral lateral superior olive (LSO),[7] where they inhibit postsynaptic neurons and provide a basis for interaural level detection (ILD), required for high frequency sound localization.[8] This synapse has been described as the largest in the brain.[9]

The related endbulb of Held is also a large axon terminal smaller synapse (15-30 µm in diameter) found in other auditory brainstem structures, namely the cochlear nucleus.[10] As with the calyces, these synapses promote fast, efficient information transfer.


  1. ^ Held, H. "Die centrale Gehörleitung" Arch. Anat. Physiol. Anat. Abt, 1893
  2. ^ Sätzler, K.; Söhl, L. F.; Bollmann, J. H.; Borst, J. G.; Frotscher, M.; Sakmann, B.; Lübke, J. H. (2002). "Three-dimensional reconstruction of a calyx of Held and its postsynaptic principal neuron in the medial nucleus of the trapezoid body". The Journal of neuroscience : the official journal of the Society for Neuroscience 22 (24): 10567–10579. PMID 12486149.  edit
  3. ^ Yang, H.; Xu-Friedman, M. A. (2013). "Stochastic Properties of Neurotransmitter Release Expand the Dynamic Range of Synapses". Journal of Neuroscience 33 (36): 14406–14416. doi:10.1523/JNEUROSCI.2487-13.2013. PMID 24005293.  edit
  4. ^ Smith, P. H.; Joris, P. X.; Carney, L. H.; Yin, T. C. T. (1991). "Projections of physiologically characterized globular bushy cell axons from the cochlear nucleus of the cat". The Journal of Comparative Neurology 304 (3): 387–407. doi:10.1002/cne.903040305. PMID 2022755.  edit
  5. ^ Smith, P. H.; Joris, P. X.; Yin, T. C. (1998). "Anatomy and physiology of principal cells of the medial nucleus of the trapezoid body (MNTB) of the cat". Journal of neurophysiology 79 (6): 3127–3142. PMID 9636113.  edit
  6. ^ Borst, J. G. G.; Soria Van Hoeve, J. (2012). "The Calyx of Held Synapse: From Model Synapse to Auditory Relay". Annual Review of Physiology 74: 199–224. doi:10.1146/annurev-physiol-020911-153236. PMID 22035348.  edit
  7. ^ Spangler, K. M.; Warr, W. B.; Henkel, C. K. (1985). "The projections of principal cells of the medial nucleus of the trapezoid body in the cat". The Journal of Comparative Neurology 238 (3): 249–262. doi:10.1002/cne.902380302. PMID 4044914.  edit
  8. ^ Tsuchitani, C. (1997). "Input from the medial nucleus of trapezoid body to an interaural level detector". Hearing research 105 (1–2): 211–224. doi:10.1016/S0378-5955(96)00212-2. PMID 9083818.  edit
  9. ^ Morest, D. K. (1968). "The collateral system of the medial nucleus of the trapezoid body of the cat, its neuronal architecture and relation to the olivocochlear bundle." Brain Res 9(2): 288-311.
  10. ^ Ryugo DK, Montey KL, Wrigth AL, Bennett ML, Pongstaporn T (2006). "Postnatal development of a large auditory nerve terminal: The endbulb of Held in cats". Hearing Research. 216-217: 100–115. doi:10.1016/j.heares.2006.01.007. PMID 16497457.