McGrath P A, Gracely R H, Dubner R, Heft M W
Pain. 1983 Apr;15(4):377-88. doi: 10.1016/0304-3959(83)90073-8.
This study investigated the quality and magnitude of sensations evoked by electrical tooth pulp stimulation. Detection threshold (the minimum current intensity that evoked a sensation) and pain threshold were determined for tooth pulp stimuli varying in frequency from 5 to 500 Hz. The effect of frequency and intensity of tooth pulp stimulation on the magnitude of sensations was assessed using visual analog scales and verbal descriptor scales. Detection thresholds were stable over experimental sessions and independent of the frequency of the stimulating current. Pain threshold varied as a function of frequency with a minimum value at 100 Hz. Stimuli that evoked non-pain sensations at low frequencies evoked pain sensations when frequency was increased from 5 to 100 Hz. Subjects were able to scale non-pain sensations over a range of stimulus intensities and frequencies. The lowest currents evoked sensations that were non-painful and were of constant magnitude despite changes in the frequency of stimulation. Higher stimulus currents evoked sensations that were non-painful at low stimulus frequencies and painful at high stimulus frequencies. Sensation magnitude at each stimulus intensity increased as a function of frequency. Temporal summation occurred in proportion to stimulus intensity. These findings suggest that the non-pain sensations evoked in tooth pulp are mediated by a distinct population of afferents that are not involved in the coding of pain. High frequency stimulation that increased the discharge rate of the lowest threshold pulpal afferents resulted in no summation of non-pain sensation and never produced pain. However, high frequency stimulation evoked greater magnitude sensations at higher stimulus currents, indicating that central summation mechanisms were critical for higher threshold afferents signaling more intense non-pain and pain sensations.
本研究调查了电刺激牙髓所诱发感觉的质量和强度。针对频率在5至500赫兹之间变化的牙髓刺激，测定了检测阈值（诱发感觉的最小电流强度）和疼痛阈值。使用视觉模拟量表和语言描述符量表评估了牙髓刺激的频率和强度对感觉强度的影响。检测阈值在实验过程中保持稳定，且与刺激电流的频率无关。疼痛阈值随频率变化，在100赫兹时达到最小值。在低频时诱发非疼痛感觉的刺激，当频率从5赫兹增加到100赫兹时会诱发疼痛感觉。受试者能够在一系列刺激强度和频率范围内对非疼痛感觉进行分级。最低电流诱发的感觉是非疼痛的，并且尽管刺激频率发生变化，其强度仍保持恒定。较高的刺激电流在低刺激频率时诱发非疼痛感觉，在高刺激频率时诱发疼痛感觉。每种刺激强度下的感觉强度随频率增加。时间总和与刺激强度成比例发生。这些发现表明，牙髓中诱发的非疼痛感觉是由一群不同的传入神经介导的，这些传入神经不参与疼痛的编码。增加最低阈值牙髓传入神经放电率的高频刺激不会导致非疼痛感觉的总和，也不会产生疼痛。然而，高频刺激在较高刺激电流时诱发更大强度的感觉，表明中枢总和机制对于更高阈值的传入神经传递更强烈的非疼痛和疼痛感觉至关重要。
