Time-dependent inhibition of hindlimb somatic afferent transmission within nucleus tractus solitarius: an in vivo intracellular recording study.
Time-dependent inhibition of hindlimb somatic afferent transmission within nucleus tractus solitarius: an in vivo intracellular recording study.
复制标题
孤束核内后肢体细胞传入传输的时间依赖性抑制：体内细胞内记录研究。
DOI：
10.1016/0306-4522(95)00156-d
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发表时间：
1995
期刊：
影响因子：
3.3
通讯作者：
Mifflin,SW
中科院分区：
文献类型：
--
作者：
Toney,GM;Mifflin,SW
在以前的研究中，我们证明了后肢躯体传入刺激引起的兴奋性反应，从孤束核神经元。当成对的电刺激传递到后肢躯体传入，单位反应的第二个刺激显着减少相比，第一个反应。这种时间响应模式被称为时间依赖性抑制，因为对第二刺激的响应随着第一刺激和第二刺激之间的间隔增加而恢复。为了研究躯体传入诱发的时间依赖性抑制的可能的突触机制，在麻醉、麻痹的大鼠孤束核神经元中进行细胞内记录。电刺激后肢右侧胫神经激活骨骼肌传入纤维，并在对侧孤束核中记录神经元反应。胫神经诱发单位放电的时间依赖性抑制进行了研究，使用条件测试刺激程序，与第一（条件）和第二（测试）刺激分开的间隔为50，150和250毫秒。在49个单位，响应胫神经刺激，46兴奋和三个被抑制。在兴奋的单位中，25个单位表现出单峰反应，其起始潜伏期为21.3 ± 5.9 ms。其余21个单位表现出双峰放电模式，其特征在于短潜伏期和长潜伏期反应。早期反应的起始潜伏期为23.7 ± 5.3ms，与单峰反应的起始潜伏期无统计学差异。迟发反应的起始潜伏期为143 ± 23.9 ms。条件测试刺激方案显示，当提前50 ms提供相同的条件刺激时，短潜伏期胫神经诱发单位对测试刺激的反应显著减少。与此相反，长潜伏期组件的双峰反应是不受条件刺激。条件试验间期≥150 ms无抑制作用。在本研究中观察到的抑制发生时没有显著的膜超极化。此外，在50 ms条件试验间期，诱发兴奋性突触后电位的去极化幅度（面积）和速率均显著降低，分别为对照组的50.7 ± 14.2和65.5 ± 15.5%。在本研究中，时间依赖性抑制的神经元反应引起的躯体传入神经元的孤束核中的神经元发生膜超极化。类似的结果也有报道，但仅限于内脏传入输入。膜对躯体和内脏输入反应的一致性表明，类似的突触机制可能介导了对这两类传入输入的时间依赖性抑制。因此，时间依赖性抑制，这似乎是一个相当刻板的反应在孤束核的神经元，可以提供一个机制，整合功能异质性输入。
In a previous study we demonstrated that hindlimb somatic afferent stimulation evokes excitatory responses from neurons in nucleus tractus solitarius. When paired electrical stimuli were delivered to hindlimb somatic afferents, the unit response to the second stimulus was significantly reduced compared with responses to the first. This temporal response pattern has been termed time-dependent inhibition since responses to the second stimulus recover as the interval separating the first and second stimuli is increased. To examine possible synaptic mechanisms for somatic afferent-evoked time-dependent inhibition, intracellular recordings were made from nucleus tractus solitarius neurons in anesthetized, paralysed rats. Skeletal muscle afferent fibers were activated by electrically stimulating the right tibial nerve in the hindlimb and neuronal responses recorded in the contralateral nucleus of the solitary tract. Time-dependent inhibition of tibial nerve-evoked unit discharge was studied using a conditioning-test stimulation procedure, with the first (conditioning) and second (test) stimuli separated by intervals of 50, 150 and 250 ms. In 49 units that responded to tibial nerve stimulation, 46 were excited and three were inhibited. Among units excited, 25 displayed a unimodal response that had an onset latency of 21.3 ± 5.9 ms. The remaining 21 units responded with a bimodal discharge pattern characterized by both a short-latency and a long-latency response. The onset latency of the early response was 23.7 ± 5.3 ms and was not statistically different from the unimodal response onset latency. The onset latency of the late response was 143 ± 23.9 ms. Conditioning-test stimulation protocols revealed that short-latency tibial nerve-evoked unit responses to test stimuli were significantly reduced when identical conditioning stimuli were delivered 50 ms earlier. In contrast, the long-latency component of the bimodal response was unaffected by conditioning stimuli. Conditioning-test intervals ≥150 ms were without inhibitory effect. Inhibitions observed in this study occurred without significant membrane hyperpolarization. Furthermore, the magnitude (area) and rate of depolarization of evoked excitatory postsynaptic potentials were both significantly reduced, to 50.7 ± 14.2 and 65.5 ± 15.5% of the control, respectively, at the 50 ms conditioning-test interval. In the present study, time-dependent inhibition of neuronal responses elicited by somatic afferent inputs to neurons in the nucleus of the solitary tract occurred without membrane hyperpolarization. Similar results have been reported, but only for visceral afferent inputs. The consistency of membrane responses to somatic and visceral inputs suggests that a similar synaptic mechanism(s) likely mediates time-dependent inhibition of both classes of afferent inputs. Thus, time-dependent inhibition, which appears to be a rather stereotype response among neurons in the nucleus of the solitary tract, could provide a mechanism for integrating functionally heterogenous inputs.