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- Title
Tonotopic Variation of the T-Type Ca<sup>2+</sup> Current in Avian Auditory Coincidence Detector Neurons.
- Authors
Ryota Fukaya; Rei Yamada; Hiroshi Kuba
- Abstract
Neurons in avian nucleus laminaris (NL) are binaural coincidence detectors for sound localization and are characterized by striking structural variations in dendrites and axon initial segment (AIS) according to their acoustic tuning [characteristic frequency (CP)]. T-type Ca2 + (CaT) channels regulate synaptic integration and firing behavior at these neuronal structures. However, whether or how CaT channels contribute to the signal processing in NL neurons is not known. In this study, we addressed this issue with whole-cell recording and two-photon Ca2+ imaging in brain slices of posthatch chicks of both sexes. We found that the CaT current was prominent in low-CF neurons, whereas it was almost absent in higher-CF neurons. In addition, a large Ca21 transient occurred at the dendrites and the AIS of low-CF neurons, indicating a localization of CaT channels at these structures in the neurons. Because low-CF neurons have long dendrites, dendritic CaT channels may compensate for the attenuation of EPSPs at dendrites. Furthermore, the short distance of AIS from the soma may accelerate activation of axonal CaT current in the neurons and help EPSPs reach spike threshold. Indeed, the CaT current was activated by EPSPs and augmented the synaptic response and spike generation of the neurons. Notably, the CaT current was inactivated during repetitive inputs, and these augmenting effects predominated at the initial phase of synaptic activity. These results suggested that dendritic and axonal CaT channels increase the sensitivity to sound at its onset, which may expand the dynamic range for binaural computation in low-CF NL neurons.
- Subjects
NEURONS; BINAURAL hearing aids; ACOUSTIC localization; DENDRIMERS; DIAGNOSTIC imaging
- Publication
Journal of Neuroscience, 2018, Vol 38, Issue 2, p335
- ISSN
0270-6474
- Publication type
Article
- DOI
10.1523/JNEUROSCI.2237-17.2017