Saksida L M, Galea L A, Kavaliers M
Department of Psychology, University of British Columbia, Vancouver, Canada.
Brain Res. 1993 Jul 23;617(2):214-9. doi: 10.1016/0006-8993(93)91088-a.
The present study examined developmental changes in the nociceptive responses of male and female meadow voles, Microtus pennsylvanicus, exposed to a garter snake, a natural predator of young voles. After 15 min of exposure to the presence of a garter snake, neonatal-juvenile voles (5-20 days of age) displayed naloxone (1.0 mg/kg)-sensitive opioid mediated analgesic responses, while after a brief 30-s exposure to the snake, voles displayed a higher amplitude, non-opioid analgesia that was insensitive to naloxone and blocked by the serotonin-1A (5-HT1A) agonist, 8-hydroxy-2-(di-n-propylamino)tetralin. The levels of opioid and non-opioid mediated analgesia declined during development as the threat presented by the snake decreased. Young female voles also displayed a significantly greater non-opioid, 5-HT1A sensitive analgesia than males, with no significant sex differences in the lower amplitude opioid analgesia. These results indicate that young (neonatal) meadow voles that are exposed to a naturally threatening stimulus display sexually dimorphic analgesic responses. These findings also illustrate the need to consider the ecological context when examining environmentally-induced analgesia.
本研究考察了雄性和雌性草原田鼠（Microtus pennsylvanicus）在接触袜带蛇（一种幼年田鼠的天然捕食者）时伤害性反应的发育变化。在接触袜带蛇15分钟后，新生至幼年田鼠（5 - 20日龄）表现出对纳洛酮（1.0毫克/千克）敏感的阿片类介导的镇痛反应，而在短暂接触蛇30秒后，田鼠表现出更高幅度的、对纳洛酮不敏感的非阿片类镇痛，且该镇痛被5-羟色胺-1A（5-HT1A）激动剂8-羟基-2-（二正丙基氨基）四氢萘阻断。随着蛇所带来的威胁降低，阿片类和非阿片类介导的镇痛水平在发育过程中下降。幼年雌性田鼠也比雄性表现出显著更强的非阿片类、5-HT1A敏感的镇痛，而在幅度较小的阿片类镇痛方面没有显著的性别差异。这些结果表明，接触自然威胁刺激的幼年（新生）草原田鼠表现出性别二态性镇痛反应。这些发现还表明，在研究环境诱导的镇痛时需要考虑生态背景。
