In vivo matching of postsynaptic excitability with spontaneous synaptic inputs during formation of the rat calyx of Held synapse

摘要

Key points class="unordered" style="list-style-type:disc" id="tjp7428-list-0001">Neurons in the medial nucleus of the trapezoid body of anaesthetized rats of postnatal day (P)2–6 showed burst firing with a preferred interval of about 100 ms, which was stable, and a second preferred interval of 5–30 ms, which shortened during development.In 3 out of 132 cases, evidence for the presence of two large inputs was found. In vivo whole‐cell recordings revealed that the excitability of the principal neuron and the size of its largest synaptic inputs were developmentally matched.At P2–4, action potentials were triggered by barrages of small synaptic events that summated to plateau potentials, while at later stages firing depended on a single, large and often prespike‐associated input, which is probably the nascent calyx of Held.Simulations with a Hodgkin–Huxley‐like model, which was based on fits of the intrinsic postsynaptic properties, suggested an essential role for the low‐threshold potassium conductance in this transition.