TY - JOUR
T1 - Dendritic HCN channels shape excitatory postsynaptic potentials at the inner hair cell afferent synapse in the mammalian cochlea
AU - Yi, Eunyoung
AU - Roux, Isabelle
AU - Glowatzki, Elisabeth
PY - 2010/5
Y1 - 2010/5
N2 - Synaptic transmission at the inner hair cell (IHC) afferent synapse, the first synapse in the auditory pathway, is specialized for rapid and reliable signaling. Here we investigated the properties of a hyperpolarization-activated current (Ih), expressed in the afferent dendrite of auditory nerve fibers, and its role in shaping postsynaptic activity. We used whole cell patch-clamp recordings from afferent dendrites directly where they contact the IHC in excised postnatal rat cochlear turns. Excitatory postsynaptic potentials (EPSPs) of variable amplitude (1-35 mV) were found with 10-90% rise times of about 1 ms and time constants of decay of about 5 ms at room temperature. Current-voltage relations recorded in afferent dendrites revealed Ih. The pharmacological profile and reversal potential (-45 mV) indicated that Ih is mediated by hyperpolarization-activated cyclic nucleotidegated cation (HCN) channels. The HCN channel subunits HCN1, HCN2, and HCN4 were found to be expressed in afferent dendrites using immunolabeling. Raising intracellular cAMP levels sped up the activation kinetics, increased the magnitude of Ih and shifted the half activation voltage (Vhalf) to more positive values (-104 ± 3 to -91 ± 2 mV). Blocking I h with 50 μM ZD7288 resulted in hyperpolarization of the resting membrane potential (∼4 mV) and slowing the decay of the EPSP by 47%, suggesting that Ih is active at rest and shortens EPSPs, thereby potentially improving rapid and reliable signaling at this first synapse in the auditory pathway.
AB - Synaptic transmission at the inner hair cell (IHC) afferent synapse, the first synapse in the auditory pathway, is specialized for rapid and reliable signaling. Here we investigated the properties of a hyperpolarization-activated current (Ih), expressed in the afferent dendrite of auditory nerve fibers, and its role in shaping postsynaptic activity. We used whole cell patch-clamp recordings from afferent dendrites directly where they contact the IHC in excised postnatal rat cochlear turns. Excitatory postsynaptic potentials (EPSPs) of variable amplitude (1-35 mV) were found with 10-90% rise times of about 1 ms and time constants of decay of about 5 ms at room temperature. Current-voltage relations recorded in afferent dendrites revealed Ih. The pharmacological profile and reversal potential (-45 mV) indicated that Ih is mediated by hyperpolarization-activated cyclic nucleotidegated cation (HCN) channels. The HCN channel subunits HCN1, HCN2, and HCN4 were found to be expressed in afferent dendrites using immunolabeling. Raising intracellular cAMP levels sped up the activation kinetics, increased the magnitude of Ih and shifted the half activation voltage (Vhalf) to more positive values (-104 ± 3 to -91 ± 2 mV). Blocking I h with 50 μM ZD7288 resulted in hyperpolarization of the resting membrane potential (∼4 mV) and slowing the decay of the EPSP by 47%, suggesting that Ih is active at rest and shortens EPSPs, thereby potentially improving rapid and reliable signaling at this first synapse in the auditory pathway.
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U2 - 10.1152/jn.00506.2009
DO - 10.1152/jn.00506.2009
M3 - Article
C2 - 20220080
AN - SCOPUS:77952996307
SN - 0022-3077
VL - 103
SP - 2532
EP - 2543
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 5
ER -