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调频声调制方向选择性与其前掩蔽的关系：小鼠下丘细胞内记录研究

付子英, 曾红, 唐佳^*, 李洁, 李娟, 陈其才

华中师范大学生命科学学院和遗传调控与整合生物学湖北省重点实验室，武汉 430079

摘要

细胞外记录研究报道听中枢神经元的调制方向选择性和前掩蔽均与神经抑制有关，但由于未能获得抑制性突触输入作用的直接证据，尚存有争议。本研究在20只昆明小鼠(Mus musculus Km)上进行在体细胞内记录，研究了下丘神经元调频声的调制方向选择性或偏好与其前掩蔽之间的关系。共获得93个下丘神经元，对其中37个产生动作电位(action potential, AP)发放且数据完整的神经元做了分析和讨论。在上扫选择性神经元(n = 12)频率调谐的高频边存在抑制性突触后电位构成的抑制区，而在下扫选择性神经元(n = 8)的低频边存在抑制区，在不具有调制方向选择性的神经元(n = 17)频率调谐的高、低频边均未观察到有明显的抑制区，表明这些抑制区是调频声调制方向选择性形成的重要原因。比较上扫和下扫调频声对上、下扫选择性和非选择性神经元的前掩蔽效应，结果显示具有调制方向选择性的神经元，其所偏好方向的调频声对最佳频率(best frequency, BF)声产生的前掩蔽强于非偏好的调频声；而无调制方向选择性神经元，上、下扫调频声的掩蔽效应无差异。以上结果提示，AP后跟随的强抑制性突触后电位可能是调制方向选择性神经元前掩蔽产生的机制。

关键词： 下丘神经元; 调频声方向选择性; 前掩蔽; 在体细胞内记录

分类号：Q959.837；Q437

[Relation between frequency modulation direction selectivity and forward masking of inferior collicular neurons: a study on in vivo intracellular recording in mice.] [Article in Chinese]

FU Zi-Ying, ZENG Hong, Tang Jia^*, LI Jie, LI Juan, CHEN Qi-Cai

School of Life Sciences and Hubei Key Laboratory of Genetic Regulation and Integrative Biology, Central China Normal University, Wuhan 430079, China

Abstract

It has been reported that the frequency modulation (FM) or FM direction sensitivity and forward masking of central auditory neurons are related with the neural inhibition, but there are some arguments, because no direct evidence of inhibitory synaptic input was obtained in previous studies using extracellular recording. In the present study, we studied the relation between FM direction sensitivity and forward masking of the inferior collicular (IC) neurons using in vivo intracellular recordings in 20 Mus musculus Km mice. Thirty seven with complete data among 93 neurons were analyzed and discussed. There was an inhibitory area which consisted of inhibitory postsynaptic potentials (IPSP) at high frequency side of frequency tuning of up-sweep FM (FM_U) sensitive neurons (n = 12) and at low frequency side of frequency tuning of down-sweep FM (FM_D) selective neurons (n = 8), while there was no any inhibitory area at both sides of frequency tuning of non-FM sweep direction (FM_N) sensitive neurons (n = 17). Therefore, these results show that the inhibitory area at low or high frequency side of frequency tuning is one of the mechanisms for forming FM sweep direction sensitivity of IC neurons. By comparison of forward masking produced by FM_U and FM_D sound stimuli in FM_U, FM_D and FM_N neurons, the selective FM sounds could produce stronger forward masking than the non-selective in FM_U and FM_D neurons, while there was no forward masking difference between FM_U and FM_D stimuli in the FM_N neurons. We suggest that the post-action potential IPSP is a potential mechanism for producing stronger forward masking in FM_U and FM_D neurons.

Key words: Inferior collicular neuron; FM direction sensitivity; forward masking; in vivo intracellular recording

收稿日期：2012-09-07　　录用日期：2012-11-18

通讯作者：唐佳　　E-mail: bobaytang@yahoo.com.cn

引用本文：

付子英, 曾红, 唐佳, 李洁, 李娟, 陈其才. 调频声调制方向选择性与其前掩蔽的关系：小鼠下丘细胞内记录研究[J]. 生理学报 2013; 65 (3): 329-337.

FU Zi-Ying, ZENG Hong, Tang Jia, LI Jie, LI Juan, CHEN Qi-Cai. [Relation between frequency modulation direction selectivity and forward masking of inferior collicular neurons: a study on in vivo intracellular recording in mice.] [Article in Chinese]. Acta Physiol Sin 2013; 65 (3): 329-337 (in Chinese with English abstract).