Central vestibular networks in the guinea-pig: Functional characterization in the isolated whole brain in vitro
Central vestibular networks in the guinea-pig: Functional characterization in the isolated whole brain in vitro
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DOI：
10.1016/s0306-4522(97)00069-9
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发表时间：
1997-11-01
期刊：
影响因子：
3.3
通讯作者：
Vidal, PP
中科院分区：
文献类型：
--
作者：
Babalian, A;Vibert, N;Vidal, PP
离体豚鼠全脑用于评估该物种前庭-眼通路的一些主要生理学和药理学特性。细胞外和细胞内的记录，从前庭，外展神经和眼神经核，以及从外展神经和眼神经，而从前庭传入，视觉通路和脊髓的输入被激活。在离体脑中还发现了先前在切片上描述的三种主要类型的前庭内侧核神经元（A、B和B+LTS）。它们在两种制剂中具有相似的膜性质。前庭神经核中85%的细胞对同侧前庭神经的刺激产生单突触兴奋性突触后电位（潜伏期1.05-1.9ms），因此被鉴定为二级前庭神经元。此外，刺激对侧前庭传入神经，在大多数情况下，揭示了双突触或三突触，连合抑制。二级前庭神经元显示在孤立的大脑中的自发活动的高度可变性，在警觉的豚鼠。PI型神经元总是表现出规则的放电，而B型和B+LTS细胞可以有非常不规则的自发放电模式。因此，A型和B型神经元可能分别对应于体内描述的强直性和相位性前庭神经元。自发放电的规律性与超极化后峰电位的幅值呈正相关，不规则神经元有从同侧前庭传入兴奋的趋势，其潜伏期较规则神经元短。突触激活可以触发一些二级前庭神经元的阈下平台电位和低阈值尖峰。作为第二步，初级前庭传入神经和二级神经元之间的突触传递的药理学进行了评估，使用特定的拮抗剂的martamatergic受体。通过单次电击刺激同侧前庭神经在前庭内侧核中引起的突触场电位和兴奋性突触后电位都被6-氰基-7-硝基喹喔啉-2，3-二酮大部分或有时完全阻断，表明α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体介导的突触能传递的主导作用。在35%的病例中，反应的其余组分被DL-2-氨基-5-膦酰基戊酸完全或部分抑制，表明N-甲基-D-戊酸受体的伴随、中度参与。此外，经常观察到对两种拮抗剂都有抗性的突触反应，但对含零Ca 2 +/高Mg 2+的溶液敏感。最后，从外展神经和眼神经复合体的录音证实了存在的豚鼠强双边，双突触兴奋性和抑制性输入前庭传入运动神经元的眼外肌，这有助于产生前庭眼反射。前庭相关通路在离体脑的功能完整性，另外检查脊髓和视神经tract.Stimulation的刺激脊髓诱发，除了在前庭神经核的逆向反应，短潜伏期的突触反应在前庭神经核和外展神经元，这表明可能的招聘脊髓传入。视交叉水平的视觉通路的激活往往会引起长潜伏期的各种结构下study.These结果表明，在体外分离的大脑可以很容易地用于详细的，功能性研究的神经网络的注视和姿势控制。(C)1997年IBRO。出版社：Elsevier Science Ltd
The isolated, in vitro whole brain of guinea-pig was used to assess some of the main physiological and pharmacological properties of the vestibule-ocular pathways in this species. Extracellular and intracellular recordings were obtained from the vestibular, abducens and oculomotor nuclei, as well as from the abducens and oculomotor nerves, while inputs from the vestibular afferents, the visual pathways and the spinal cord were activated. The three main types of medial Vestibular nucleus neurons (A, B and B+LTS), previously described on slices, were also identified in the isolated brain. They had similar membrane properties in both preparations. Eighty-five per cent of cells recorded in the vestibular nucleus responded with monosynaptic, excitatory postsynaptic potentials (latency 1.05-1.9ms) to stimulation of the ipsilateral vestibular nerve, and were thus identified as second-order vestibular neurons. In addition, stimulation of the contralateral vestibular afferents revealed in most cases a disynaptic or trisynaptic, commissural inhibition. Second-order vestibular neurons displayed in the isolated brain a high degree of variability of their spontaneous activity, as in alert guinea-pigs. Type PI neurons always exhibited a regular firing, while type B and B+LTS cells could have very irregular patterns of spontaneous discharge. Thus, type A and type B neurons might correspond, respectively, to the tonic and phasic vestibular neurons described in vivo. The regularity of spontaneous discharge was positively correlated with the amplitude of spike after hyperpolarization, and there was a trend for irregular neurons to be excited from ipsilateral vestibular afferents at shorter latencies than regular units. Synaptic activation could trigger subthreshold plateau potentials and low-threshold spikes in some of the second-order vestibular neurons. As a second step, the pharmacology of the synaptic transmission between primary vestibular afferents and second-order neurons was assessed using specific antagonists of the glutamatergic receptors. Both the synaptic field potentials and excitatory postsynaptic potentials elicited in the medial vestibular nucleus by single shock stimulation of the ipsilateral vestibular nerve were largely or, sometimes, totally blocked by 6-cyano-7-nitroquinoxaline-2,3-dione, indicating a dominating role of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated glutamatergic transmission. The remaining component of the responses was completely or partially suppressed by DL-2-amino-5-phosphonovaleric acid in 35% of the cases, suggesting a concomitant, moderate involvement of N-methyl-D-asparate receptors. In addition, a synaptic response resistant to both antagonists; but sensitive to a zero Ca2+/high Mg2+ containing solution, was often observed. Finally,recordings from abducens and oculomotor complexes confirmed the existence in the guinea-pig of strong bilateral, disynaptic excitatory and inhibitory inputs from vestibular afferents to motoneurons of extraocular muscles, which contribute to generation of the vestibule-ocular reflex. The functional integrity of vestibular-related pathways in the isolated brain was additionally checked by stimulation of the spinal cord and optic tract.Stimulation of the spinal cord evoked, in addition to antidromic responses in the vestibular nucleus, short-latency synaptic responses in both the vestibular nucleus and abducens motoneurons, suggesting possible recruitment of spinal afferents. Activation of visual pathways at the level of the optic chiasm often induced long latency responses in the various structures under study.These results demonstrate that the in vitro isolated brain can be readily used for detailed, functional studies of the neuronal networks underlying gaze and posture control. (C) 1997 IBRO. Published by Elsevier Science Ltd.