Laboratoire de Neurobiologie des Réseaux Sensorimoteur, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7060, Université Paris 5, Paris Cédex 06, France.
J Neurosci. 2010 Mar 3;30(9):3310-25. doi: 10.1523/JNEUROSCI.5318-09.2010.
Central vestibular neurons receive substantial inputs from the contralateral labyrinth through inhibitory and excitatory brainstem commissural pathways. The functional organization of these pathways was studied by a multi-methodological approach in isolated frog whole brains. Retrogradely labeled vestibular commissural neurons were primarily located in the superior vestibular nucleus in rhombomeres 2/3 and the medial and descending vestibular nucleus in rhombomeres 5-7. Restricted projections to contralateral vestibular areas, without collaterals to other classical vestibular targets, indicate that vestibular commissural neurons form a feedforward push-pull circuitry. Electrical stimulation of the contralateral coplanar semicircular canal nerve evoked in canal-related second-order vestibular neurons (2 degrees VN) commissural IPSPs (approximately 70%) and EPSPs (approximately 30%) with mainly (approximately 70%) disynaptic onset latencies. The dynamics of commissural responses to electrical pulse trains suggests mediation predominantly by tonic vestibular neurons that activate in all tonic 2 degrees VN large-amplitude IPSPs with a reversal potential of -74 mV. In contrast, phasic 2 degrees VN exhibited either nonreversible, small-amplitude IPSPs (approximately 40%) of likely dendritic origin or large-amplitude commissural EPSPs (approximately 60%). IPSPs with disynaptic onset latencies were exclusively GABAergic (mainly GABA(A) receptor-mediated) but not glycinergic, compatible with the presence of GABA-immunopositive (approximately 20%) and the absence of glycine-immunopositive vestibular commissural neurons. In contrast, IPSPs with longer, oligosynaptic onset latencies were GABAergic and glycinergic, indicating that both pharmacological types of local inhibitory neurons were activated by excitatory commissural fibers. Conservation of major morpho-physiological and pharmacological features of the vestibular commissural pathway suggests that this phylogenetically old circuitry plays an essential role for the processing of bilateral angular head acceleration signals in vertebrates.
中枢前庭神经元通过抑制性和兴奋性脑桥连合通路从对侧迷路接收大量输入。通过分离青蛙全脑的多方法方法研究了这些通路的功能组织。逆行标记的前庭连合神经元主要位于 2/3 节段的上前庭核和 5-7 节段的内侧和下降前庭核。对侧前庭区的受限投射，没有对其他经典前庭靶标的侧支，表明前庭连合神经元形成前馈推拉电路。对侧共面半规管神经的电刺激在与管相关的二阶前庭神经元（2 度 VN）中诱发连合 IPSP（约 70%）和 EPSP（约 30%），主要（约 70%）具有双突触起始潜伏期。对电脉冲串的连合反应的动力学表明，主要由激活所有紧张性 2 度 VN 大振幅 IPSP 的紧张性前庭神经元介导，其反转电位为-74 mV。相比之下，相位性 2 度 VN 表现出非可逆的、小振幅 IPSP（约 40%），可能来源于树突，或者大振幅连合 EPSP（约 60%）。具有双突触起始潜伏期的 IPSP 仅为 GABA 能（主要为 GABA(A)受体介导），而不是甘氨酸能，与存在 GABA 免疫阳性（约 20%）和缺乏甘氨酸免疫阳性前庭连合神经元相容。相比之下，具有较长、寡突触起始潜伏期的 IPSP 为 GABA 能和甘氨酸能，表明兴奋性连合纤维激活了两种药理学类型的局部抑制性神经元。前庭连合通路的主要形态生理学和药理学特征的保守性表明，这种在进化上古老的电路在脊椎动物双侧角加速度信号的处理中发挥着重要作用。
