Paton J F, Ramirez J M, Richter D W
Physiologisches Institut, Universität Göttingen, Germany.
Pflugers Arch. 1994 Oct;428(3-4):250-60. doi: 10.1007/BF00724504.
The present report describes a novel rhythmically active brainstem slice preparation that generates respiratory activity spontaneously in both mice and rats of varying maturational states. The brainstems of neonatal (0-4 days) and mature (3-8 weeks) mice and rats were isolated and a 600- to 750-microns thick slice cut to include the dorsomedial and the ventrolateral regions of the complete rostro-caudal extent of the medulla. This plane of section we have termed "tilted-sagittal". Rhythmically discharging neurones were recorded extracellularly from both the dorsal and ventral regions of the slice. The recording sites of these neurones were found in the hypoglossal motonucleus (XII) and in areas of the ventrolateral medulla that includes the ventral respiratory group (VRG) region. Histological examination revealed the preservation of neuronal structures important for cardiorespiratory regulation and reflex control including the nucleus of the solitary tract as well as the nucleus ambiguus. In addition, pontine structures including the A5 region were also preserved. Rhythmic activity was found only in slices where the ambiguual column was preserved in its entirety. The mean frequency of discharge of XII neurones was 20 and 10 bursts per minute in neonates and mature rodents respectively. In preparations of mature animals we demonstrate that this frequency increased significantly (P < 0.05) by either raising temperature from 29 degrees C to 38 degrees C (54%), elevating extracellular potassium concentration from 4 to 7.5 mM (52%), blocking potassium channels (20%) or decreasing pH from 7.4 to 7.0 (18%). The burst duration to frequency ratio of XII and VRG rhythmic neurones was similar and therefore indicative of a common brainstem oscillator. Consistent with this finding was that rhythmic activity in the VRG persisted despite removal of the dorsomedial region of the slice. In contrast, rhythmic XII neurones became tonic following mechanical disconnection of the VRG.
本报告描述了一种新型的有节律活动的脑干切片标本，该标本能在不同成熟状态的小鼠和大鼠中自发产生呼吸活动。分离新生（0 - 4天）和成熟（3 - 8周）小鼠及大鼠的脑干，切成600至750微米厚的切片，以包括延髓完整前后范围的背内侧和腹外侧区域。我们将这个切片平面称为“倾斜矢状面”。从切片的背侧和腹侧区域细胞外记录有节律放电的神经元。这些神经元的记录位点位于舌下运动核（XII）以及延髓腹外侧包括腹侧呼吸组（VRG）区域的部位。组织学检查显示，对心肺调节和反射控制重要的神经元结构得以保留，包括孤束核以及疑核。此外，包括A5区域在内的脑桥结构也得以保留。仅在疑核柱完整保留的切片中发现有节律活动。新生小鼠和成熟啮齿动物中XII神经元的平均放电频率分别为每分钟20次和10次爆发。在成熟动物的标本中，我们证明通过将温度从29摄氏度升高到38摄氏度（增加54%）、将细胞外钾浓度从4毫摩尔升高到7.5毫摩尔（增加52%）、阻断钾通道（增加20%）或使pH从7.4降至7.0（增加18%），该频率会显著增加（P < 0.05）。XII和VRG节律性神经元的爆发持续时间与频率之比相似，因此表明存在一个共同的脑干振荡器。与此发现一致的是，尽管切除了切片的背内侧区域，VRG中的节律活动仍持续存在。相反，在VRG机械断开连接后，节律性的XII神经元变为紧张性。
