ENCODING OF ELECTRICAL, THERMAL, AND MECHANICAL NOXIOUS STIMULI BY SUBNUCLEUS RETICULARIS DORSALIS NEURONS IN THE RAT MEDULLA
ENCODING OF ELECTRICAL, THERMAL, AND MECHANICAL NOXIOUS STIMULI BY SUBNUCLEUS RETICULARIS DORSALIS NEURONS IN THE RAT MEDULLA
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DOI：
10.1152/jn.1989.61.2.391
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发表时间：
1989-02-01
影响因子：
2.5
通讯作者：
LEBARS, D
中科院分区：
文献类型：
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作者：
VILLANUEVA, L;BING, Z;LEBARS, D
在麻醉大鼠，记录内的延髓网状背侧亚核（SRD）的神经元，表现出从整个身体的伤害性输入的收敛。具有总伤害性会聚（TNC）的神经元对阈上经皮电刺激（2-ms持续时间）作出反应，由于A δ-1的激活而具有早峰和晚峰。和C-纤维，分别，无论身体的哪个部位受到刺激。具有局部非伤害性会聚（PNC）的神经元对相同刺激的反应为A δ-无论身体的哪个部位受到刺激，都有一个C峰，主要是对侧的身体部位。这些神经元的反应的特点进行了分析的应用程序的梯度强度的电，热和机械刺激。所有的TNC神经元和85%的PNC神经元对A δ-和对侧后爪的经皮电刺激后的C-纤维激活。关于A δ-纤维诱发的反应，在0.25-和6.0-mA和0.5- 24-mA的范围内，TNC和PNC神经元，分别被发现的应用电流的对数和响应的幅度之间的线性关系，然而，这些曲线基本上是相似的。关于C-纤维诱发的反应，这种线性关系被发现在1.5- 6.0 mA的范围内的两种类型的SRD神经元，虽然TNC神经元提出了更大的C-纤维诱发的反应比PNC神经元。在44 - 52 ℃的范围内，在对侧后爪施加伤害性热刺激期间，TNC和PNC神经元线性增加它们的放电;由伤害性热从TNC神经元诱发的平均反应比从PNC神经元诱发的反应具有更高的幅度。大多数SRD神经元在放电后表现出持久性，特别是在所采用的最高温度（52 ℃）下。TNC神经元在分级机械或热刺激的尾巴单调增加其放电。当施加机械刺激时，在5.3- 7.4-N/cm 2范围内，发现机械刺激强度的对数与神经元放电之间存在线性关系。通过热刺激，TNC神经元在44 - 52 ℃范围内线性增加其放电。当将越来越多的尾浸入50 ℃水浴中时，TNC神经元在尾表面积的有限范围内（0.9- 5.7cm 2）增加了它们的放电;刺激表面尺寸的进一步增加并不伴随着放电速率的增加。它的结论是，SRD神经元编码的强度的电或自然刺激的身体范围内，可以被视为有害的。由于SRD神经元的响应的特性，建议对该结构的至少一些输入源自A δ-以及对有害的机械或机械和热刺激有反应的C-伤害感受器和背角（会聚和伤害特异性）神经元。尽管有这些编码特性，SRD神经元不太可能发挥作用的感觉歧视方面的疼痛，已提出的脊髓丘脑系统;由于大量的异节段收敛到SRD神经元，它建议，他们可能有助于自主反应和/或情感情绪反应相关的疼痛。
In anesthetized rats, recordings were made within the medullary subnucleus reticularis dorsalis (SRD) from neurons that exhibited convergence of nociceptive inputs from the entire body. Neurons with total nociceptive convergence (TNC) responded to suprathreshold percutaneous electrical stimuli (2-ms duration) with an early and a late peak due to activation of A.delta.- and C-fibers, respectively, no matter which part of the body was stimulated. Neurons with parial nonciceptive convergence (PNC) responded to the same stimuli with an A.delta.-peak regardless of which part of the body was stimulated and with a C-peak of activation from some, mainly contralateral, parts of the body. The characteristics of the responses of these neurons to the application of graded intensities of electrical, thermal, and mechanical stimuli were analyzed. All TNC neurons and 85% of PNC neurons responded to A.delta.- and C-fiber activation following percutaneous electrical stimulation of the contralateral hindpaw. With regard to A.delta.-fiber-evoked responses, a linear relationship between the logarithm of the applied current and the magnitude of the responses was found within the 0.25- and 6.0-mA and 0.5- to 24-mA ranges for TNC and PNC neurons, respectively; however, these curves were essentially similar. With regard to C-fiber-evoked responses, such a linear relationship was found within the 1.5- to 6.0-mA range for both types of SRD neurons, although the TNC neurons presented larger C-fiber-evoked responses than did PNC neurons. TNC and PNC neurons linearly increased their discharges during the application of noxious thermal stimuli to the contralateral hindpaw within the range 44-52.degree.C; the mean responses evoked by noxious heat from TNC neurons were of higher magnitude than those from PNC neurons. The majority of SRD neurons presented long-lasting after discharges, especially with the highest temperature employed (52.degree.C). TNC neurons monotonically increased their discharges during graded mechanical or thermal stimulation of the tail. When mechanical stimuli were applied, a linear relationship was found between the logarithm of the strength of the mechanical stimulus and the neuronal discharges, in the 5.3- to 7.4-N/cm2 range. With thermal stimulation, TNC neurons linearly increased their discharges in the 44-52.degree.C range. When increasing amounts of the tail were immersed in a 50.degree.C waterbath, TNC neurons increased their discharges within a restricted range of tail surface areas (0.9-5.7 cm2); further increases in the stimulated surface size were not followed by increases in firing rate. It is concluded that SRD neurons encode the strength of electrical or natural stimulation of the body within ranges that can be regarded as noxious. Owing to the characteristics of the response of SRD neurons, it is suggested that at least some of the inputs to this structure originate from A.delta.- and C-nociceptors responsive to noxious mechanical or mechanical and heat stimuli and dorsal horn (convergent and noxious-specific) neurons. Despite these encoding properties, SRD neurons are not likely to play a role in the sensory-discriminative aspects of pain as has been proposed for the spinothalamic system; owing to the massive heterosegmental convergence onto SRD neurons, it is suggested that they might contribute to autonomic reactions and/or to affective-emotional responses related to pain.