Schenk S, Robinson B
Texas A & M University, Department of Psychology, College Station 77843.
Behav Brain Res. 1988 Dec 1;31(2):105-10. doi: 10.1016/0166-4328(88)90012-5.
Stimulation of periaqueductal gray sites resulted in both increased latencies to escape heated water with a tail-flick and audible vocalizations. To determine whether these two responses were the result of stimulation of the same substrates, refractory periods were estimated by delivering paired-pulse trains of stimulation. Stimulation consisted of 10 or 20 s trains of single pulses or pulse pairs. The pulse pair frequency threshold for both behaviors was determined for intra-pulse (C-T) intervals of 0.4-10 ms. The ratio of single to double pulse frequency thresholds provided an indication of relative effectiveness of the paired-pulse stimulation. For analgesia, the paired-pulse effectiveness gradually increased between C-T intervals of 2.0 and 5.0 ms, after which asymptotic effectiveness values were obtained. Thus, the estimated refractory period for analgesia was 2.0-5.0 ms. The refractory period estimate for vocalizations was shorter. Effectiveness values increased with a C-T interval of 1.2 ms and reached asymptote with a C-T interval of 2.0 ms. These results suggest that different fibers with overlapping spatial distributions contribute to analgesia and vocalizations produced by midbrain stimulation.
对导水管周围灰质部位的刺激导致尾巴轻弹以逃离热水的潜伏期增加以及可听见的发声。为了确定这两种反应是否是由相同底物的刺激引起的，通过传递成对脉冲刺激序列来估计不应期。刺激由10或20秒的单脉冲或脉冲对序列组成。对于0.4 - 10毫秒的脉冲内（C - T）间隔，确定了两种行为的脉冲对频率阈值。单脉冲与双脉冲频率阈值的比率提供了成对脉冲刺激相对有效性的指示。对于镇痛，在2.0至5.0毫秒的C - T间隔之间，成对脉冲有效性逐渐增加，之后获得渐近有效性值。因此，镇痛的估计不应期为2.0 - 5.0毫秒。发声的不应期估计较短。有效性值在C - T间隔为1.2毫秒时增加，并在C - T间隔为2.0毫秒时达到渐近值。这些结果表明，具有重叠空间分布的不同纤维对中脑刺激产生的镇痛和发声有贡献。
