Calyx of Held

Calyx of Held microstructure

The calyx of Held is a particularly large excitatory synapse in the mammalian auditory nervous system, so named after Hans Held who first described it in his 1893 article Die centrale Gehörleitung[1][2] because of its resemblance to the calyx of a flower.[3] Globular bushy cells in the anteroventral cochlear nucleus (AVCN)[4] send axons to the contralateral medial nucleus of the trapezoid body (MNTB), where they synapse via these calyces on MNTB principal cells.[5][6][7] These principal cells then project to the ipsilateral lateral superior olive (LSO),[8] where they inhibit postsynaptic neurons and provide a basis for interaural level detection (ILD), required for high frequency sound localization.[9] This synapse has been described as the largest in the brain.[10]

The related endbulb of Held is also a large axon terminal synapse (15–30 μm in diameter) found in another auditory brainstem structure, namely the anteroventral cochlear nucleus (AVCN).[11] As with the calyces, these synapses promote fast, efficient information transfer.

The calyx of Held and endbulb of Held hold vesicles containing glutamate on the presynaptic terminal; the vesicles are released upon stimulation (originating in the cochlea and AVCN). The glutamate then binds to two known glutamate receptors, AMPA- and NMDA receptors, rapidly initiating action potentials in the post-synaptic cell.[12]

Commonly used in research due to its large size, the calyx of Held has been used to understand a variety of mechanisms related to development of, and vesicle release of the synapse.

  1. ^ Held, H. "Die centrale Gehörleitung" Arch. Anat. Physiol. Anat. Abt, 1893
  2. ^ Ryugo, David K.; Spirou, George A. (2017-01-01), "Giant Synaptic Terminals: Endbulbs and Calyces of the Auditory System☆", Reference Module in Neuroscience and Biobehavioral Psychology, Elsevier, ISBN 978-0-12-809324-5, retrieved 2021-03-05
  3. ^ 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. 22 (24): 10567–10579. doi:10.1523/JNEUROSCI.22-24-10567.2002. PMC 6758464. PMID 12486149. S2CID 18520148.
  4. ^ 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. PMC 3761050. PMID 24005293.
  5. ^ 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. S2CID 18844385.
  6. ^ 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. doi:10.1152/jn.1998.79.6.3127. PMID 9636113.
  7. ^ 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.
  8. ^ 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. S2CID 35642962.
  9. ^ 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. S2CID 4780393.
  10. ^ 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. doi:10.1016/0006-8993(68)90235-7. PMID 5679830.
  11. ^ Ryugo DK, Montey KL, Wright 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. S2CID 4676902.
  12. ^ Cite error: The named reference Borst2012B was invoked but never defined (see the help page).