Edwards Ian J, Dallas Mark L, Poole Sarah L, Milligan Carol J, Yanagawa Yuchio, Szabó Gábor, Erdélyi Ferenc, Deuchars Susan A, Deuchars Jim
Institute of Membrane and Systems Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
J Neurosci. 2007 Aug 1;27(31):8324-33. doi: 10.1523/JNEUROSCI.0638-07.2007.
Sensory afferent signals from neck muscles have been postulated to influence central cardiorespiratory control as components of postural reflexes, but neuronal pathways for this action have not been identified. The intermedius nucleus of the medulla (InM) is a target of neck muscle spindle afferents and is ideally located to influence such reflexes but is poorly investigated. To aid identification of the nucleus, we initially produced three-dimensional reconstructions of the InM in both mouse and rat. Neurochemical analysis including transgenic reporter mice expressing green fluorescent protein in GABA-synthesizing neurons, immunohistochemistry, and in situ hybridization revealed that the InM is neurochemically diverse, containing GABAegric and glutamatergic neurons with some degree of colocalization with parvalbumin, neuronal nitric oxide synthase, and calretinin. Projections from the InM to the nucleus tractus solitarius (NTS) were studied electrophysiologically in rat brainstem slices. Electrical stimulation of the NTS resulted in antidromically activated action potentials within InM neurons. In addition, electrical stimulation of the InM resulted in EPSPs that were mediated by excitatory amino acids and IPSPs mediated solely by GABA(A) receptors or by GABA(A) and glycine receptors. Chemical stimulation of the InM resulted in (1) a depolarization of NTS neurons that were blocked by NBQX (2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonoamide) or kynurenic acid and (2) a hyperpolarization of NTS neurons that were blocked by bicuculline. Thus, the InM contains neurochemically diverse neurons and sends both excitatory and inhibitory projections to the NTS. These data provide a novel pathway that may underlie possible reflex changes in autonomic variables after neck muscle spindle afferent activation.
来自颈部肌肉的感觉传入信号被假定为作为姿势反射的组成部分影响中枢心肺控制，但这种作用的神经通路尚未确定。延髓中间核（InM）是颈部肌肉梭形传入神经的靶点，其位置理想，可影响此类反射，但研究较少。为了有助于识别该核，我们最初制作了小鼠和大鼠InM的三维重建模型。神经化学分析包括在GABA合成神经元中表达绿色荧光蛋白的转基因报告小鼠、免疫组织化学和原位杂交，结果显示InM在神经化学上具有多样性，包含GABA能和谷氨酸能神经元，与小白蛋白、神经元型一氧化氮合酶和钙视网膜蛋白有一定程度的共定位。在大鼠脑干切片中用电生理学方法研究了从InM到孤束核（NTS）的投射。电刺激NTS导致InM神经元内出现逆向激活的动作电位。此外，电刺激InM导致由兴奋性氨基酸介导的兴奋性突触后电位（EPSP）以及仅由GABA(A)受体或由GABA(A)和甘氨酸受体介导的抑制性突触后电位（IPSP）。化学刺激InM导致：（1）被NBQX（2,3 - 二氧代 - 6 - 硝基 - 1,2,3,4 - 四氢苯并[f]喹喔啉 - 7 - 磺酰胺）或犬尿氨酸阻断的NTS神经元去极化，以及（2）被荷包牡丹碱阻断的NTS神经元超极化。因此，InM包含神经化学性质多样的神经元，并向NTS发送兴奋性和抑制性投射。这些数据提供了一条新的通路，可能是颈部肌肉梭形传入神经激活后自主变量反射性变化的基础。
