Wilson J R, Howard B A
Department of Psychology, University of Manitoba, Winnipeg, Canada.
Pharmacol Biochem Behav. 1996 Jun;54(2):317-25. doi: 10.1016/0091-3057(95)02124-8.
Two experiments, using centrally administered [D-Ala2-MePhe4-Gly(ol)5]enkephalin (DAMGO), a selective mu-opioid agonist, assessed the thermoregulatory consequences of cold acclimation. Experiment 1 assessed whether cold acclimation influenced DAMGO hyperthermia at room temperature. Sialo-adenectomized rats were implanted with ICV cannulae and IP Mini-Mitters. After 3 weeks of exposure to 5 degrees C (cold acclimation) or 22 degrees C (non-cold acclimation) rats were pretreated with IP naltrexone HCl (2 mg/kg b.wt.) or vehicle (0.15 M saline) and later administered a 5-microliters ICV injection of 0.15 M saline, 0.1, or 1.0 microgram DAMGO. Cold acclimation exerted little effect on core temperature but potentiated DAMGO hyperthermia in a dose-dependent, naltrexone-reversible, activity-independent manner. Experiment 2 assessed the effect these same manipulations exerted on operant escape from a convective source of mild heat (37 degrees C). Duration of heat escape increased with cold acclimation in a naltrexone-resistant manner, yet was not influenced by DAMGO in either non-cold-acclimated or cold-acclimated rats. These findings suggest that two central adaptations occur with cold acclimation: A non-mu-opioid process that increases heat sensitivity and a mu-opioid process that potentiates hyperthermia but fails to alter heat escape due to mu-opioid-mediated analgesia.
两项实验使用中枢给药的[D - 丙氨酸2 - 甲基苯丙氨酸4 - 甘氨酸（醇）5]脑啡肽（DAMGO，一种选择性μ阿片受体激动剂）评估了冷适应对体温调节的影响。实验1评估了冷适应是否会影响室温下DAMGO引起的体温过高。对唾液腺切除的大鼠植入脑室内套管和腹腔内微型温度记录器。在暴露于5摄氏度（冷适应）或22摄氏度（非冷适应）3周后，大鼠接受腹腔注射盐酸纳曲酮（2毫克/千克体重）或赋形剂（0.15 M生理盐水）预处理，随后脑室内注射5微升0.15 M生理盐水、0.1或1.0微克DAMGO。冷适应对核心体温影响不大，但以剂量依赖性、纳曲酮可逆、与活动无关的方式增强了DAMGO引起的体温过高。实验2评估了相同操作对从温和热源（37摄氏度）进行操作性逃避的影响。随着冷适应，热逃避的持续时间以纳曲酮抵抗的方式增加，但在非冷适应或冷适应的大鼠中均不受DAMGO影响。这些发现表明，冷适应会出现两种中枢适应性变化：一种是非μ阿片受体过程，可增加热敏感性；另一种是μ阿片受体过程，可增强体温过高，但由于μ阿片受体介导的镇痛作用而未能改变热逃避。
