Misra B R, Klein B G
Department of Biomedical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, 24061, USA.
Somatosens Mot Res. 1995;12(1):11-28. doi: 10.3109/08990229509063139.
We have previously demonstrated increases in serotonin (5-HT) content and immunoreactivity within spinal trigeminal subnucleus interpolaris (SpVi) that are correlated with the functional changes observed in this subnucleus following adult infraorbital nerve (ION) transection. To assess the possible functional significance of this change, we have examined the influence of 5-HT afference upon the normal response properties of cells in SpVi. We employed local depletion of the transmitter, using 5,7-dihydroxtryptamine (5,7-DHT), in combination with extracellular single-cell recording. Chromatographic methods revealed a 97.6% depletion of 5-HT 24 hr after neurotoxin injection. Immunocytochemical procedures revealed depletion of 5-HT throughout SpVi. Physiological recordings were made from 403 SpVi cells in 5,7-DHT-injected rats and 387 cells in vehicle-injected rats. All recordings were made 19-27 hr after injection. Horseradish peroxidase (HRP) deposits from the recording electrode were used to mark recording tracks. 5-HT depletion did not influence receptive field (RF) location, size, or continuity, or the dynamic response characteristics of SpVi cells. It did, however, (1) alter the probability that certain types of somatosensory receptor surfaces would activate local-circuit neurons, and (2) influence the rate of firing of spontaneously active SpVi cells. There was a significant increase in the proportion of vibrissa-sensitive cells with infraorbital RF components, and a concurrent decrease in the proportion of guard-hair-sensitive cells. It therefore appears that 5-HT input to SpVi is necessary for some mechanoreceptive features of the normal functional organization of this area. These functional changes were interesting in that they were opposite to those found following adult ION transection, which increases 5-HT within SpVi. Thus, changes in 5-HT central afference to SpVi that follow ION damage may be responsible for at least one type of functional change observed following this peripheral lesion.
我们之前已经证明，成年眶下神经（ION）横断后，脊髓三叉神经中极亚核（SpVi）内5-羟色胺（5-HT）含量及免疫反应性增加，且与该亚核中观察到的功能变化相关。为评估这种变化可能的功能意义，我们研究了5-HT传入对SpVi中细胞正常反应特性的影响。我们采用5,7-二羟色胺（5,7-DHT）进行递质局部耗竭，并结合细胞外单细胞记录。色谱法显示，神经毒素注射24小时后5-HT耗竭了97.6%。免疫细胞化学方法显示SpVi内5-HT耗竭。对注射5,7-DHT的大鼠的403个SpVi细胞和注射溶剂的大鼠的387个细胞进行了生理记录。所有记录均在注射后19 - 27小时进行。记录电极的辣根过氧化物酶（HRP）沉积用于标记记录轨迹。5-HT耗竭不影响感受野（RF）位置、大小或连续性，也不影响SpVi细胞的动态反应特性。然而，它确实（1）改变了某些类型的躯体感觉受体表面激活局部回路神经元的概率，以及（2）影响了自发活动的SpVi细胞的放电率。具有眶下RF成分的触须敏感细胞比例显著增加，同时触毛敏感细胞比例相应减少。因此，SpVi的5-HT输入对于该区域正常功能组织的某些机械感受特征是必要的。这些功能变化很有趣，因为它们与成年ION横断后发现的变化相反，后者会增加SpVi内的5-HT。因此，ION损伤后SpVi的5-HT中枢传入变化可能是该外周损伤后观察到的至少一种功能变化的原因。
