Developmental mechanisms from tetal to neonatal type of respiratory center as a functional neuron network

我们分析了胎鼠延髓呼吸神经元的内源性爆发产生特性。在E17-20的准备，显示胎儿C4型吸气爆发模式，约60%的吸气神经元表现出电压依赖性爆发活动。在E19的制备中，爆发神经元的输入电阻显著高于非爆发细胞。膜电容往往是较低的（但不显着）在爆裂神经元比在非爆裂细胞。由于爆发神经元在低Ca ~（2+）/高Mg ~（2+）溶液中仍保持爆发活动，因此我们认为它们具有内在爆发产生特性。在E20/21组中，呼吸神经元活动出现在延髓头端腹外侧区的有限区域（面旁呼吸组，pFRG），并主要向尾侧传播。 关于我们 y.然后，在吸气阶段，活动的峰值被检测到，尾部，在尾侧腹外侧延髓（CVLM），喙，在主要的外侧和内侧区域的面神经核。该模式与新生大鼠制剂的模式基本相同。相反，在所有的E17和大多数E18制剂中，呼吸活动首先出现在CVLM区域，与吸气爆发的开始一致，然后向嘴侧传播。随后，面神经核的整个区域出现强活动，并在C_4吸气活动终止后持续1-3秒。在一半的E19制备物中，呼吸活动从pFRG（新生儿型）开始，而从CVLM（胎儿型）开始。然而，即使在显示新生儿型网络活动模式的制剂中，C4吸气活动也是显示短爆发持续时间的胎儿型。我们认为，初级节律产生网络和时空模式发展到新生儿型之前，神经元网络产生吸气活动。少

We analyzed intrinsic burst generating property of respiratory neurons in the medulla of the rat fetus. In the E17-20 preparations that showed the fetal type-C4 inspiratory burst pattern, about 60% of inspiratory neurons exhibited voltage-dependent burst activity. In E19 preparations, the input resistance of the bursting neurons was significantly higher than that of non-bursting cells. Membrane capacitance tended to be lower (but not significant) in the bursting neurons than in the non-bursting cells. Since the bursting neurons still kept the bursting activity in the low Ca2+/high Mg2+ solution, we concluded that they possess intrinsic burst generating properties.Using optical recordings, we analyzed respiratory neuron network activity in the ventral medulla of fetus stained with voltage-sensitive dye. In E20/21 preparations, respiratory neuron activity appeared in the limited area of the rostral ventrolateral medulla (para-facial respiratory group, pFRG), and propagated mainly caudall … More y. Then, during the inspiratory phase, the peak of activity was detected, caudally, in the caudal ventrolateral medulla (CVLM) and, rostrally, in the mainly lateral and medial region of the facial nucleus. Such pattern was basically identical to that of neonatal rat preparations. In contrast, in all of El7 and most of El8 preparations, respiratory activity first appeared in the CVLM region, coincidently with the start of inspiratory burst, and then propagated rostrally. Successively, strong activity appeared in the whole region of the facial nucleus and continued 1-3 sec after termination of C4 inspiratory activity. In half of E19 preparations, respiratory activity started from the pFRG (neonatal type), whereas it started from the CVLM inothers (fetal type). However, even in the preparations that showed the neonatal type-network activity pattern, C4 inspiratory activity was the fetal type showing short burst duration. We suggest that the primary rhythm generating network and the spatio-temporal pattern develops to the neonatal type before the neuron network generating inspiratory activity does. Less