[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.
Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China.
Yun
Y
Zhu
Wei-Jia
WJ
Kong
Jiao
J
Xia
Yu
Y
Zhang
Hua-Mao
HM
Cheng
Chang-Kai
CK
Guo
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