Philpot B D, Foster T C, Brunjes P C
Department of Psychology, University of Virginia, Charlottesville 22903, USA.
J Neurobiol. 1997 Oct;33(4):374-86. doi: 10.1002/(sici)1097-4695(199710)33:4<374::aid-neu3>3.0.co;2-7.
Patterned neural activity helps to establish neuronal connectivity, produce coding of sensory information, and shape synaptic strengths. Here we demonstrate that normal olfactory bulb development might rely on spatial and temporal patterns of afferent neural activity. Neonatal naris occlusion profoundly impacts the development of the ipsilateral olfactory bulb, including reduced bulb volume, decreased protein synthesis, and increased cell death. Relatively few morphologic changes occur if closure is performed postweaning. We examined the immediate electrophysiological consequences of occlusion across this developmentally sensitive period by recording spontaneous and odor-driven mitral/tufted cell responses while the naris was open, closed, and then reopened. In 1-week-old animals, occlusion severely attenuated spontaneous activity, and presentation of the broad-spectrum odorant amyl acetate failed to evoke responses. In 2- and 4-week old rats, spontaneous activity was also reduced by naris closure. However, some cells remained responsive to concentrated odors, even in animals with transected anterior commissures, suggesting passage of odors across the septal window or retronasal pathways. In all age groups, cellular activity became uncoupled from the respiratory cycle. Approximately 47% (18 of 38) of the mitral/tufted cells exhibited activity that was correlated with respiration in the open-naris state, while only 5% (2 of 38) were coupled during naris closure. These data (a) indicate that naris closure reduces both spontaneous and odor-evoked responses, and (b) provide an electrophysiological correlate to a sensitive period in bulb development. The loss of respiration-related synchrony and the reduced activity of mitral/tufted cells may synergistically contribute to the diverse consequences of naris closure on bulb development.
有规律的神经活动有助于建立神经元连接、产生感觉信息编码并塑造突触强度。在此，我们证明正常的嗅球发育可能依赖于传入神经活动的空间和时间模式。新生动物鼻孔闭塞会严重影响同侧嗅球的发育，包括嗅球体积减小、蛋白质合成减少以及细胞死亡增加。如果在断奶后进行闭塞，则形态学变化相对较少。我们通过记录鼻孔开放、闭合及随后重新开放时自发的和气味驱动的二尖瓣/簇状细胞反应，研究了在这个发育敏感期闭塞所带来的即时电生理后果。在1周龄的动物中，闭塞严重减弱了自发活动，并且广谱气味剂乙酸戊酯的呈现未能引发反应。在2周龄和4周龄的大鼠中，鼻孔闭合也降低了自发活动。然而，一些细胞仍然对浓缩气味有反应，即使在前连合横断的动物中也是如此，这表明气味通过鼻中隔窗或鼻后通路传递。在所有年龄组中，细胞活动与呼吸周期解耦。在鼻孔开放状态下，约47%（38个中的18个）的二尖瓣/簇状细胞表现出与呼吸相关的活动，而在鼻孔闭合期间只有5%（38个中的2个）是耦合的。这些数据（a）表明鼻孔闭合会降低自发反应和气味诱发反应，（b）为嗅球发育中的敏感期提供了电生理关联。呼吸相关同步性的丧失以及二尖瓣/簇状细胞活动的减少可能协同导致鼻孔闭合对嗅球发育产生的多种后果。
