Transient BK outward current enhances motoneurone firing rates during Drosophila larval locomotion

摘要

Key points class="unordered" style="list-style-type:disc" id="tjp6831-list-0001">We combine in situ electrophysiology with genetic manipulation in Drosophila larvae aiming to investigate the role of fast calcium‐activated potassium currents for motoneurone firing patterns during locomotion.We first demonstrate that slowpoke channels underlie fast calcium‐activated potassium currents in these motoneurones.By conducting recordings in semi‐intact animals that produce crawling‐like movements, we show that slowpoke channels are required specifically in motoneurones for maximum firing rates during locomotion.Such enhancement of maximum firing rates occurs because slowpoke channels prevent depolarization block by limiting the amplitude of motoneurone depolarization in response to synaptic drive. In addition, slowpoke channels mediate a fast afterhyperpolarization that ensures the efficient recovery of sodium channels from inactivation during high frequency firing.The results of the present study provide new insights into the mechanisms by which outward conductances facilitate neuronal excitability and also provide direct confirmation of the functional relevance of precisely regulated slowpoke channel properties in motor control.