Blass E M, Jackson A M, Smotherman W P
Department of Psychology, Cornell University, Ithaca, New York 14853.
Behav Neurosci. 1991 Oct;105(5):677-86. doi: 10.1037/0735-7044.105.5.667.
Four experiments were conducted in rats within 2 hr of cesarean delivery to assess antinociception at birth and its possible opioid bases. Morphine antinociception was established in a dose-dependent fashion (0.0625-5.0 mg/kg bw). Analgesia was naloxone (1.0 mg/kg) reversible. In succeeding experiments, antinociception equivalent to that produced by 0.0625-0.125 mg/kg morphine injections was induced by a single 20-microliters bolus of milk (commercial half-and-half) that was delivered over 1-2 s to the middle of the tongue. This, too, was naloxone reversible. Milk-induced antinociception was maintained for at least 4 min. Finally, baseline latencies were progressively reduced during the first 2 hr after delivery to levels (8-10 s) that are typically obtained in older (10-day-old) rats. This decline was not opioid mediated because it was not affected by naloxone. Thus, at birth, delivering milk to the mouth in physiological volumes can exert opioid-mediated antinociceptive effects in rats born by cesarean delivery that had never suckled or experienced any other form of maternal contact.
剖宫产术后2小时内在大鼠身上进行了四项实验，以评估出生时的抗伤害感受及其可能的阿片类物质基础。吗啡的抗伤害感受呈剂量依赖性（0.0625 - 5.0毫克/千克体重）。镇痛作用可被纳洛酮（1.0毫克/千克）逆转。在后续实验中，单次20微升的乳剂（市售半脱脂奶）以1 - 2秒的时间推注到舌头中部，可诱导出与0.0625 - 0.125毫克/千克吗啡注射产生的抗伤害感受相当的效果。这一效果同样可被纳洛酮逆转。乳汁诱导的抗伤害感受至少持续4分钟。最后，出生后最初2小时内基线潜伏期逐渐缩短至（8 - 10秒），这一水平通常在较大（10日龄）大鼠中获得。这种下降并非由阿片类物质介导，因为它不受纳洛酮影响。因此，在出生时，以生理体积将乳汁输送到口中可在剖宫产出生且从未哺乳或经历过任何其他形式母体接触的大鼠中产生阿片类物质介导的抗伤害感受作用。
