[Properties of cholinergic receptor-mediated ion channels on type I vestibular hair cells of guinea pigs].
To confirm the existence of cholinergic receptors on type I vestibular hair cells (VHCs I) of guinea pigs and to study the properties of the cholinergic receptor-mediated ion channels on VHCs I, electrophysiological responses of isolated VHCs I to external ACh were examined by means of whole-cell patch-clamp recordings. The results showed that 7.5% (21/279) VHCs I were found to be sensitive to ACh (10-1000 μmol/L). ACh generated an outward current in a steady, slow, dose-dependent [EC(50) was (63.78±2.31) μmol/L] and voltage-independent manner. In standard extracellular solution, ACh at the concentration of 100 μmol/L triggered a calcium-dependent current of (170±15) pA at holding potential of -50 mV, and the current amplitude could be depressed by extracellularly added calcium-dependent potassium channel antagonist TEA. The time interval for the next complete activation of ACh-sensitive current was no less than 1 min. The ion channels did not shut off even when they were exposed to ACh for an extended period of time (8 min). The results suggest that dose-dependent, calcium-dependent and voltage-independent cholinergic receptors were located on a few of the VHCs I investibular epithelium of guinea pigs. The cholinergic receptors did not show desensitization to ACh. This work reveals the existence of efferent neurotransmitter receptors on VHCs I and helps in understanding the function of vestibular efferent nervous system, and may provide some useful information on guiding the clinical rehabilitative treatment of vertigo.
Zhu
Yun
Y
Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
Kong
Wei-Jia
WJ
Xia
Jiao
J
Zhang
Yu
Y
Cheng
Hua-Mao
HM
Guo
Chang-Kai
CK
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D006168:Guinea Pigs; D018069:Hair Cells, Vestibular / Q000502:physiology*; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology; D011950:Receptors, Cholinergic / Q000502:physiology*
D026902:Potassium Channel Blockers; D024681:Potassium Channels, Calcium-Activated; D011950:Receptors, Cholinergic; D000109:Acetylcholine