RHYTHMIC SPONTANEOUS ACTIVITY IN THE DEVELOPING AVIAN AUDITORY-SYSTEM
RHYTHMIC SPONTANEOUS ACTIVITY IN THE DEVELOPING AVIAN AUDITORY-SYSTEM
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DOI：
10.1523/jneurosci.14-03-01486.1994
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发表时间：
1994-03-01
影响因子：
5.3
通讯作者：
LIPPE, WR
中科院分区：
文献类型：
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作者：
LIPPE, WR
在孵化 14 至 19 d 期间 (E14-E19)，用小鸡听觉系统中的大细胞核 (NM) 和板层核 (NL)、二级和三级核进行自发多单位活动的微电极记录。 E14-E18 胚胎中的自发放电以周期性间隔以同步爆发的形式发生。在听觉神经中也观察到自发放电的节律模式，但在脑干的非听觉区域中没有观察到。 NM 和 NL 的平均爆发间隔从 E14-E15 的 4.9 秒减少到 E18 的 2.1 秒。到 E19，孵化前 2 天，同步爆发被无模式、稳定的放电水平所取代，与孵化鸟的 NM 和 NL 中存在的背景放电相当。爆裂与心跳或呼吸无关，并且不受中耳小骨移除的影响。节奏爆发可以通过声音刺激来重置、阻止或诱导。耳蜗切除或用 TTX 对听觉神经活动进行药物阻断可消除爆裂。这些结果表明脉冲发射的同步性和节律性反映了正常的生理活动，最有可能是耳蜗起源。目前的研究结果表明，胚胎鸟类听觉系统中的自发活动，就像未成熟的哺乳动物视觉通路中的自发活动一样（Maffei和Galli-Resta，1990；Meister等人，1991），以同步节律模式发生。这种相似性提出了这种活动可能是早期感觉系统发育的普遍特征的可能性。雏鸡的模式化自发放电发生在胚胎发生期间，此时听觉阈值较高，并且卵内的生理功能不太可能受到空气中正常发生的声音水平的显着影响。在同一时期，脑干听觉神经元的结构和神经支配发生了巨大的变化。据推测，自发放电的时间模式可能提供有助于这些发育事件的线索。
Microelectrode recordings of spontaneous multiple unit activity were made from nucleus magnocellularis (NM) and nucleus laminaris (NL), second- and third-order nuclei in the chick auditory system, between 14 and 19 d of incubation (E14-E19). Spontaneous firing in E14-E18 embryos occurred in synchronous bursts at periodic intervals. A rhythmic pattern of spontaneous firing was also observed in the auditory nerve but not in nonauditory regions of the brainstem. The mean interburst interval in NM and NL decreased from 4.9 sec at E14-E15 to 2.1 sec at E18. By E19, 2 d prior to hatching, synchronous bursting was replaced by an unpatterned, steady level of firing comparable to the background discharge that is present in NM and NL of hatchling birds. Bursting was not correlated with heart beat or respiration and was not affected by removal of the middle-ear ossicle. Rhythmic bursting could be reset, blocked, or induced by sound stimulation. Cochlea removal or pharmacological blockade of auditory nerve activity with TTX eliminated bursting. These results indicate that the synchrony and rhythmicity of impulse firing reflect normal physiological activity, most likely of cochlear origin.The present findings show that spontaneous activity in the embryonic avian auditory system, like that in the immature mammalian visual pathway (Maffei and Galli-Resta, 1990; Meister et al., 1991), occurs in a synchronously rhythmic pattern. This similarity raises the possibility that such activity may be a general feature of early sensory system development. Patterned spontaneous firing in the chick takes place during a period of embryogenesis when auditory thresholds are high and when it is unlikely that physiological function in ovo is influenced significantly by normally occurring levels of airborne sound. Brainstem auditory neurons undergo substantial changes in structure and innervation during this same period. It is speculated that the temporal pattern of spontaneous discharge may provide cues that contribute to these developmental events.