Reinke H, Wild J M
Department of Anatomy, School of Medicine, University of Auckland, New Zealand.
J Comp Neurol. 1997 Mar 17;379(3):347-62.
We have recorded extracellular, inspiratory-related (IR) unit activity in the medulla at locations corresponding to those of neurons retrogradely labeled by injections of retrograde tracers in the lower brachial and upper thoracic spinal cord, injections that covered cell bodies and dendrites of motoneurons innervating inspiratory muscles. Bulbospinal neurons were distributed throughout the dorsomedial and ventrolateral medulla, from the spinomedullary junction through about 0.8 mm rostral to the obex. Almost all of the 104 IR units recorded were located in corresponding parts of the ventrolateral medulla, rostral to nucleus retroambigualis, where expiratory related units are found. Injections of biotinylated dextran amine at the recording sites labeled projections both to the spinal cord and to the brainstem. In the lower brachial and upper thoracic spinal cord, bulbospinal axons traveled predominantly in the contralateral dorsolateral funiculus and terminated in close relation to the dendrites of inspiratory motoneurons retrogradely labeled with cholera toxin B-chain. In the brainstem, there were predominantly ipsilateral projections to the nucleus retroambigualis, tracheosyringeal motor nucleus (XIIts), ventrolateral nucleus of the rostral medulla, infraolivary superior nucleus, ventrolateral parabrachial nucleus, and dorsomedial nucleus of the intercollicular complex. In all these nuclei, except XIIts, retrogradely labeled neurons were also found, indicating reciprocity of the connections. These results suggest the possibility of monosynaptic connections between inspiratory premotor neurons and inspiratory motoneurons, which, together with connections of IR neurons with other brainstem respiratory-vocal nuclei, seem likely to mediate the close coordination that exists in birds between the vocal and respiratory systems. The distribution of IR neurons in birds is similar to that of the rostral ventral respiratory group (rVRG) in mammals.
我们在延髓中记录了与吸气相关（IR）的细胞外单位活动，记录位置对应于通过向臂下和胸上脊髓注射逆行示踪剂而被逆行标记的神经元位置，这些注射覆盖了支配吸气肌肉的运动神经元的细胞体和树突。延髓脊髓神经元分布于整个背内侧和腹外侧延髓，从脊髓延髓交界处到闩前方约0.8毫米处。记录的104个IR单位几乎都位于腹外侧延髓的相应部位，在疑后核的前方，呼气相关单位也位于此处。在记录部位注射生物素化葡聚糖胺标记了投射到脊髓和脑干的纤维。在臂下和胸上脊髓，延髓脊髓轴突主要走行于对侧背外侧索，并终止于与用霍乱毒素B链逆行标记的吸气运动神经元的树突密切相关的部位。在脑干，主要有同侧投射到疑后核、气管注射器运动核（XIIts）、延髓头端腹外侧核、橄榄下上核、臂旁腹外侧核和间丘复合体背内侧核。在所有这些核中，除了XIIts，还发现了逆行标记的神经元，表明连接具有相互性。这些结果提示吸气前运动神经元和吸气运动神经元之间可能存在单突触连接，这与IR神经元与其他脑干呼吸-发声核的连接一起，似乎可能介导了鸟类发声和呼吸系统之间存在的紧密协调。鸟类中IR神经元的分布与哺乳动物的头端腹侧呼吸组（rVRG）相似。
