Price D D, Hayes R L, Ruda M, Dubner R
Fed Proc. 1978 Jul;37(9):2237-9.
Temporal summation of second pain and long-lasting tactile-evoked aftersensations are examples of sensory phenomenons that cannot be explained on the basis of responses of primary afferents. Two distinct classes of monkey spinothalamic tract neurons have responses to controlled natural stimuli that parallel and thus could account for the above phenomenons. One class, termed wide-dynamic-range, receives excitatory effects from sensitive mechanoreceptive afferents and from various nociceptive afferents including Adelta and C mechanothermal nociceptive afferents. Another class, termed nociceptive-specific, receives excitatory effects exclusively from primary nociceptive afferents. Both classes respond with an early and late response to a single noxious heat pulse (peak temperature = 51 C). The late response, unlike C nociceptive afferents but like second pain, summates in magnitude with each successive heat pulse. Gentle moving tactile stimuli evoke long-lasting (20-56 sec) after-discharges only in wide dynamic range neurons, and are similar in duration to the tactile after-sensation evoked by similar stimuli. Both the after-discharges and after-sensations can be abruptly terminated by rubbing the affected region. Temporal summation of second pain and cutaneous after-sensations are at least partly subserved by spinal cord mechanisms within the dorsal horn and are manifested in the output of spinothalamic tract neurons.
第二痛觉的时间总和以及持久的触觉诱发后感觉是无法基于初级传入神经的反应来解释的感觉现象的例子。两类不同的猴脊髓丘脑束神经元对受控自然刺激有反应，这些反应与上述现象相似，因此可以解释这些现象。一类称为广动力范围神经元，它从敏感的机械感受器传入神经以及包括Aδ和C机械热伤害性传入神经在内的各种伤害性传入神经接收兴奋性作用。另一类称为伤害性特异性神经元，仅从初级伤害性传入神经接收兴奋性作用。这两类神经元对单个有害热脉冲（峰值温度 = 51℃）都有早期和晚期反应。与C伤害性传入神经不同，但与第二痛觉相似，晚期反应的幅度会随着每个连续的热脉冲而累加。轻柔的移动触觉刺激仅在广动力范围神经元中诱发持久的（20 - 56秒）后放电，其持续时间与类似刺激诱发的触觉后感觉相似。后放电和后感觉都可以通过摩擦受影响区域而突然终止。第二痛觉和皮肤后感觉的时间总和至少部分由脊髓背角内的脊髓机制维持，并在脊髓丘脑束神经元的输出中表现出来。
