Temperature enhances exocytosis efficiency at the mouse inner hair cell ribbon synapse.
Hearing relies on fast and sustained neurotransmitter release from inner hair cells (IHCs) onto the afferent auditory nerve fibres. The temperature dependence of Ca(2+) current and transmitter release at the IHCs ribbon synapse has not been investigated thus far. To assess the influence of temperature on calcium-triggered exocytosis, patch-clamp recordings of voltage-gated L-type Ca(2+) influx and exocytic membrane capacitance changes were performed at room (25 degrees C) and physiological (35-37 degrees C) temperatures. An increase in temperature within this range increased the L-type Ca(2+) current amplitude of IHCs (Q(10) = 1.3) and accelerates the activation kinetics. Fast exocytosis, probed by 20 ms depolarization, was enhanced at physiological temperature with a Q(10) of 2.1. The amplitude of fast release was elevated disproportionately to the increase in Ca(2+) influx. In contrast, the rate of sustained exocytosis (exocytic rate between 20 and 100 ms of depolarization) did not show a significant increase at physiological temperature. Altogether, these data indicate that the efficiency of fast exocytosis is higher at physiological temperature than at room temperature and suggest that the number of readily releasable vesicles available at the active zone is higher at physiological temperature.
Nouvian
Régis
R
InnerEarLab, Department of Otolaryngology, Center for Molecular Physiology of the Brain, Bernstein Center fot Computational Neuroscience, Göttingen University Medical School, Robert-Koch-Strasse 40, 37075 Göttingen, Germany. nouvian@med.uni-goettingen.de
D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling; D003056:Cochlear Nerve / Q000378:metabolism*; D025802:Electric Capacitance; D005089:Exocytosis; D006199:Hair Cells, Auditory, Inner / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D018377:Neurotransmitter Agents / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D013569:Synapses / Q000378:metabolism*; D009435:Synaptic Transmission; D013572:Synaptic Vesicles / Q000378:metabolism*; D013696:Temperature
D020746:Calcium Channels, L-Type; D018377:Neurotransmitter Agents
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