On the role of subtypes of muscarinic receptors in the inner ear

今年，我们在过去两年的基础上继续进行研究。然而，我们在年初遇到了两个麻烦。首先，由于流行病问题，被淘汰动物的供应中断了大约半年。11月恢复了稳定的供应，我们恢复了实验。其次，与此同时，美国的一个竞争实验室报告说，他们的小鼠缺乏毒菌素受体（与我们的基因敲除无关的产物），听力几乎正常，对耳毒性药物也有类似的易感性（Maison SF, et al. 2005）。然而，我们在两点上取得了进展。首先，我们修改了从去年开始一直悬而未决的记录oae的计算机软件，使动物和人类都可以记录dpoae。其次，考虑到上述情况，我们尝试将内耳的研究轴从听觉系统转移到前庭系统，最终在全细胞膜片钳模式下，我们能够记录啮齿类动物前庭神经节细胞的动作电位。我们还通过DNA阵列揭示了毒蕈碱受体mrna在前庭神经节细胞中的表达。近期计划的研究：1)我们仍在继续用敲除小鼠和野生型小鼠对异常噪声和耳毒性药物易感性的比较研究实验。这是因为研究结果可能与美国研究小组的结果不同，因为基因敲除小鼠是独立产生的。2)由于啮齿类动物前庭神经节细胞上存在毒蕈碱受体，我们计划首先研究毒蕈碱受体对神经元兴奋性的调节，然后揭示敲除小鼠和野生型小鼠神经元放电模式的差异。此外，通过研究离子通道对动作电位形成的贡献差异，推断毒蕈碱受体对前庭神经节细胞发育过程的贡献。少

This year, we continued our research on the basis of what we have established during the past two years. However, we encountered two troubles at the beginning of the year. First, because of epidemic problems, supply of the knock-out animals was disconnected for about half a year. The stable supply was re-established in November and we resumed the experiments. Secondly, in the meantime, a competing laboratory in the States reported that their mice lacking muscarinic receptors (product independent of our knock-outs) had almost normal hearing and similar susceptibility to ototoxic agents (Maison SF, et al. 2005).However, we made progress in two points. First, we revised the computer software to record OAEs, which was a pending problem from the last year, and enabled recording DPOAEs in animals as well as in humans. Secondly, considering the situation described above, we tried to shift the axis of our research in the inner ear from the auditory system to the vestibular system and finally w … More ere able to record action potentials of vestibular ganglion cells in rodents on the whole-cell patch clamp mode. We also revealed the expression of mRNAs for muscarinic receptors in vestibular ganglion cells by means of DNA arrays.Planned studies in the near future :1) We still continue the experiments on comparative studies on susceptibility to extraordinary noise and to ototoxic drugs using knock-out and wild-type mice. This is because the results may differ from those from the USA group, since the knock-out mice were independently produced.2) Since the existence of muscarinic receptors on the vestibular ganglion cells in rodents was indicated, we plan first to investigate modulation of excitability of neurons by muscarinic receptors and then to reveal the difference of neuronal firing patterns between knock-out and wild-type mice. Moreover, by investigating the difference in contribution of ionic channels on action potential formation, the contribution of muscarinic receptors to developmental processes of vestibular ganglion cells will be deduced. Less