Bodnar R J, Kelly D D, Steiner S S, Glusman M
Pharmacol Biochem Behav. 1978 Jun;8(6):661-6. doi: 10.1016/0091-3057(78)90263-0.
Animals exposed to cold-water swims, rotation, inescapable shocks, abrupt food deprivation and other stressors display temporary analgesia. Since repeated exposures result in adaptation of this analgesia in much the same way that repeated administration of opiates results in tolerance, the possibility of cross-tolerance between cold-water stress-induced and morphine-induced analgesia was investigated. Flinch-jump thresholds were determined in ten experimental groups of six rats each. Three groups showed dose-dependent analgesia following single injections of morphine at 5, 10 and 15 mg/kg, respectively. A fourth group, subjected to a single cold-water swim at 2 degrees C for 3.5 min, displayed analgesia comparable to that produced by 10 mg/kg of morphine. Groups subjected either to 14 daily cold-water swims or to 14 daily morphine injections at 10 mg/kg showed normal thresholds on the 14th day indicating that adaptation and tolerance had developed, respectively. The cross-over groups were exposed to either 13 days of could-water swims followed by morphine or the reverse arrangement. Both groups showed profound analgesia instead of cross-tolerance, suggesting that a non-opiate neural mechanism may mediate stress-induced analgesia.
暴露于冷水游泳、旋转、不可逃避的电击、突然的食物剥夺及其他应激源的动物会表现出暂时的镇痛作用。由于重复暴露会导致这种镇痛作用产生适应性，其方式与重复给予阿片类药物导致耐受性的方式非常相似，因此研究了冷水应激诱导的镇痛作用与吗啡诱导的镇痛作用之间交叉耐受性的可能性。在十个实验组中测定了退缩跳跃阈值，每组有六只大鼠。三组分别单次注射5、10和15mg/kg吗啡后呈现剂量依赖性镇痛作用。第四组在2摄氏度下单次冷水游泳3.5分钟，表现出与10mg/kg吗啡产生的镇痛作用相当的效果。每天进行14次冷水游泳或每天注射10mg/kg吗啡共14天的组在第14天显示出正常阈值，分别表明已经产生了适应性和耐受性。交叉组要么先进行13天的冷水游泳，然后注射吗啡，要么采用相反的安排。两组均表现出深度镇痛而非交叉耐受性，这表明一种非阿片类神经机制可能介导应激诱导的镇痛作用。
