Newby-Schmidt M B, Norton S
Pharmacol Biochem Behav. 1981 Nov;15(5):773-8. doi: 10.1016/0091-3057(81)90021-6.
Tolerance to morphine was produced in the chick embryo. Eggs were injected with morphine sulfate (MS) (20 mg/kg egg) or H2O daily starting on incubation day 12. On day 16, embryo activities were recorded and eggs were injected with either MS or naloxone. Activity of H2O-pretreated controls decreased after both MS and naloxone. Embryos treated with MS from incubation days 12-15 showed no activity change after morphine and responded to naloxone with increases in activity. Baseline rates of distress vocalizations (DV) of 1-2 day old chicks were not affected by MS pretreatment during incubation days 12-19. However, 1 mg/kg MS decreased the rate of DV of control chicks by 90% whereas MS-pretreated chicks were unaffected. At age 4-5 days, the baseline rate of DV and rate after MS were higher in MS-pretreated chicks. However, all chicks showed significant decreases in rate of DV after MS injection. Naloxone increased the rate of DV of paired 1-2 day old chicks, but response of MS-pretreated chicks was significantly greater than controls.
在鸡胚中产生了对吗啡的耐受性。从孵化第12天开始，每天给鸡蛋注射硫酸吗啡（MS）（20毫克/千克鸡蛋）或水。在第16天，记录胚胎活动，并给鸡蛋注射MS或纳洛酮。水预处理对照组在注射MS和纳洛酮后活动均减少。在孵化第12 - 15天用MS处理的胚胎，在注射吗啡后活动无变化，而对纳洛酮有反应，活动增加。孵化第12 - 19天期间，MS预处理对1 - 2日龄雏鸡的痛苦叫声（DV）基线率没有影响。然而，1毫克/千克的MS使对照雏鸡的DV率降低了90%，而MS预处理的雏鸡则不受影响。在4 - 5日龄时，MS预处理雏鸡的DV基线率和注射MS后的比率更高。然而，所有雏鸡在注射MS后DV率均显著下降。纳洛酮增加了配对的1 - 2日龄雏鸡的DV率，但MS预处理雏鸡的反应明显大于对照组。
