아세틸콜린이 외유모세포 칼륨 전류 및 길이 변화에 미치는 영향

Abstract

Background and Objectives：Iner hair cells (IHCs) of the organ of Corti change the external sound stimulus into the elect-rical signal and transmit this signal to the auditory cortex through afferent nerve fibers. Outer hair cels (OHCs) control the sound transmission function of IHC. OHCs respond with a somatic shape change to alterations in their membrane potential and this electromotile response is believed to provide mechanical fedback to the basilar membrane. Eferent nerve fibers which arise from the superior olivary nucleus in the midbrain and transmit to OHCs through medial olivocochlear bundle use acetylcholine (ACh) as a neurotransmiter. The cholinergic response of OHCs α-9 nicotinic ACh receptor increase the Ca2+ influx, which control OHCs electromotility by changing a membrane potential. In this research, the effect of ACh on the K+ current in OHC of guinea pig was studied, and the change of OHC length by ACh was studied. Materials and Methods：Using the extracted change of OHC length when ACh was applied was observed. Results：1) ACh increases voltage-dependent K+ current in OHC. 2) In the condition, which Ca2+-dependent K+ current is blocked by removing Ca2+ from intra-cellular fluid, ACh has no effect on K+ current in OHC. 3) ACh increases OHC length. Conclusion：These experimental results show that ACh from the medial olivocochlear eferent system regulates mobility of OHC, increases the Ca2+-dependent K+ currents in OHC.