Temporal processing of aortic nerve evoked activity in the nucleus of the solitary tract.
Temporal processing of aortic nerve evoked activity in the nucleus of the solitary tract.
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主动脉神经的时间处理引起孤束核的活动。
DOI：
10.1152/jn.1996.76.6.3750
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Mifflin,SW
中科院分区：
文献类型：
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作者：
Scheuer,DA;Zhang,J;Toney,GM;Mifflin,SW
1. 孤立束（NTS）神经元核对异质性传入信号的时间处理已经被描述过。研究人员对26只戊巴比妥钠麻醉的雄性sd大鼠进行了实验，以表征主动脉神经（仅包含动脉压力感受器传入纤维）对NTS神经元诱发活动的时间处理。2. 在电刺激主动脉神经时，在NTS中检测细胞外单细胞活动，使用条件测试范式。3. 从49个神经元中获得结果，其中22个神经元接受来自主动脉神经传入的单突触输入。单突触神经元的平均诱发电位数为1.1 +/- 0.1，多突触神经元的平均诱发电位数为1.2 +/- 0.2。自发活动平均为3.7±0.7 Hz。没有神经元表现出明显的脉冲节律性放电。单突触细胞的平均峰值潜伏期为17 +/- 2 ms（范围3 ~ 31 ms），显著短于多突触细胞的平均峰值潜伏期26 +/- 1 ms（范围13 ~ 38 ms） （P < 0.05）。与多突触细胞相比，单突触细胞的平均起病潜伏期变异也更小（4 +/- 1 ms vs. 8 +/- 1 ms; P < 0.05）。4. 以接受来自主动脉传入的单突触输入为特征的神经元通常不表现出时间依赖性抑制。仅在调节测试间隔50 ms时观察到显著的抑制作用，平均测试反应为对照的79 +/- 8%。相比之下，接受主动脉神经多突触输入的神经元在50毫秒的调节测试间隔后的平均反应仅为对照组的32 +/- 8%。调节测试间隔达200 ms时，观察到显著的抑制作用。在条件反射间隔为50 ms时，22个单突触神经元中只有5个被>抑制50%。在调节测试过程中，这些神经元的平均动脉压明显低于被抑制< 50%的17个细胞。这表明收敛传入输入的活动水平可能会影响时间依赖性抑制的大小。6. 在所有条件反射测试间隔中，多突触神经元从时间依赖性抑制中明显呈现线性恢复，这表明存在可变持续时间的单一机制。本文报道的结果与目前的理论一致，即时间依赖性抑制是由失易化介导的。7. 结果表明，NTS神经元接受来自主动脉降压神经的单突触输入时很少表现出时间依赖性抑制。这可以让原始的、未经修改的传入信息分散到后续的神经元。相比之下，接受多突触输入的神经元经历了与其他传入输入相似的时间依赖性抑制。这可以允许不同程度的保真度在传入信息转移到特定的传出途径。因此，单个压力感受器传入的放电时间模式可能在动脉压力反射的功能中发挥关键作用，从而在血压调节中发挥关键作用。
1. Temporal processing of heterogenous afferent signals by nucleus of the solitary tract (NTS) neurons has been previously characterized. Experiments were performed in 26 pentobarbital-sodium-anesthetized male Sprague-Dawley rats to characterize the temporal processing of evoked activity in NTS neurons with the use of the aortic nerve, which contains exclusively arterial baroreceptor afferent fibers. 2. Extracellular single-cell activity was examined in the NTS during electrical stimulation of the aortic nerve with the use of a conditioning-test paradigm. 3. Results were obtained from 49 neurons, 22 of which were characterized as receiving monosynaptic input from aortic nerve afferents. The average number of evoked potentials per aortic nerve stimulation was 1.1 +/- 0.1 (SE) for the monosynaptic neurons and 1.2 +/- 0.2 for the polysynaptic neurons. Spontaneous activity averaged 3.7 +/- 0.7 Hz. No neuron exhibited an obvious pulse-rhythmic discharge. The average peak onset latency for monosynaptic cells of 17 +/- 2 ms (range 3-31 ms) was significantly (P < 0.05) shorter than the average of 26 +/- 1 ms (range 13-38 ms) for the polysynaptic cells. The average onset latency variability was also less in monosynaptic compared with polysynaptic cells (4 +/- 1 ms vs. 8 +/- 1 ms; P < 0.05). 4. Neurons characterized as receiving a monosynaptic input from the aortic afferents generally did not exhibit time-dependent inhibition. Significant inhibition was observed only at a conditioning-test interval of 50 ms, when the average test response was 79 +/- 8% of control. In contrast, the average response following a 50-ms conditioning-test interval for neurons receiving polysynaptic input from the aortic nerve was only 32 +/- 8% of control. Significant inhibition was observed at conditioning-test intervals of up to 200 ms. 5. At a conditioning-test interval of 50 ms, only 5 of 22 monosynaptic neurons were inhibited by > 50%. Mean arterial pressure during the conditioning-test procedure was significantly lower for these neurons than for the 17 cells that were inhibited by < 50%. This suggests that the level of activity in convergent afferent input might influence the magnitude of time-dependent inhibition. 6. There was an essentially linear recovery from time-dependent inhibition evident in polysynaptic neurons that were tested at all conditioning-test intervals, suggesting a single mechanism of variable duration. Results reported here are consistent with current theory that time-dependent inhibition is mediated by disfacilitation. 7. The results demonstrate that NTS neurons receiving monosynaptic input from the aortic depressor nerve infrequently exhibit time-dependent inhibition. This could allow for the original, unmodified afferent information to be dispersed to subsequent neurons. In contrast, neurons receiving polysynaptic input undergo time-dependent inhibition similar to that which has been reported for other afferent inputs. This could allow for differential degrees of fidelity in the transfer of the afferent information to specific efferent pathways. Therefore the temporal pattern of firing in individual baroreceptor afferents could play a critical role in the function of the arterial baroreflex and therefore in the regulation of blood pressure.