抄録
Voltage-dependent K+ currents regulate transmitter release by repolarizing the nerve terminal. Among many types of K+ channels, high voltage-activated Kv3 channels and low voltage-activated Kv1 channels are abundantly expressed at the calyx of Held nerve terminal in the auditory brainstem of rodents. During early postnatal development, calyceal synapses undergo a variety of morphological and functional changes. Here we asked whether voltage-dependent K+ channels in calyceal terminals undergo developmental changes and whether they contribute to functional maturation of this auditory synapse. From postnatal day (P) 7 to P14, the density of Kv1 and Kv3 K+ currents increased in parallel and their activation kinetics also accelerated. Simulation of calyx action potential indicated that both changes in the kinetics and density of K+ channels contribute to shortening of action potential duration. Selective block of Kv3 or Kv1 channels at both P7 and P15 indicated that developmental changes in Kv3 channels contributes to high-fidelity firing at high frequency, whereas the developmental increase in Kv1 currents stabilizes the nerve terminal thereby preventing aberrant firing of action potentials. We conclude that developmental changes in both Kv3 and Kv1 channels in the nerve terminal contribute to maturation of high-fidelity fast synaptic transmission at this auditory relay synapse. [J Physiol Sci. 2007;57 Suppl:S153]
