Cox B, Ary M, Lomax P
Pharmacol Biochem Behav. 1976 Mar;4(3):259-62. doi: 10.1016/0091-3057(76)90238-0.
Thermoregulatory behavior was assessed in the rat by measuring the time taken to escape from a radiant heat source. The time to excape and the rise in core temperature accompanying exposure to heat were greater in morphine dependent (1 X 75 mg SC pellet implant for 72 hr) than in control rats. Injection of naloxone (1 mg/kg) into dependent rats produced a withdrawal hypothermia and decreased the time taken to escape from the heat source. Since rats undergoing withdrawal avoided heat at the same time that their core temperature was falling, the hypothermia is most likely due to a downward setting of the central thermostats rather than a direct activation of heat loss pathways. Both the withdrawal hypothermia and the behavioral changes were blocked by pimozide pretreatment (0.5 mg/kg) implicating a dopaminergic mechanism in the downward setting of the thermostats. Administration of naloxone 144 hr after pellet implantation produced similar effects to those in the 72 hr implanted group. Injection of morphine sulfate (4 mg/kg) 144 hr after implantation increased both the core temperature and the time taken to escape from heat suggesting that the effect of morphine in the dependent rat is to produce an upward setting of the thermostats.
通过测量大鼠从辐射热源逃脱所需的时间来评估体温调节行为。吗啡依赖大鼠（皮下植入1×75mg丸剂，持续72小时）从热源逃脱的时间以及受热时核心体温的升高幅度均大于对照大鼠。向依赖大鼠注射纳洛酮（1mg/kg）会导致戒断性体温过低，并缩短从热源逃脱所需的时间。由于经历戒断的大鼠在核心体温下降的同时会躲避热源，因此体温过低很可能是由于中枢恒温器的设定值下调，而非热散失途径的直接激活。哌迷清预处理（0.5mg/kg）可阻断戒断性体温过低和行为变化，这表明恒温器设定值下调涉及多巴胺能机制。在植入丸剂144小时后注射纳洛酮产生的效果与72小时植入组相似。植入144小时后注射硫酸吗啡（4mg/kg）会使核心体温和从热源逃脱所需的时间均增加，这表明吗啡对依赖大鼠的作用是使恒温器设定值上调。
