Coover G D, Sutton B R, Heybach J P
J Comp Physiol Psychol. 1977 Aug;91(4):716-26. doi: 10.1037/h0077363.
This study examined the nature of a stimulus-induced decrease in the plasma corticosterone levels of rats. Rats maintained on a 23-hr food and water deprivation regimen were fed each morning immediately upon entrance of the experimenter into the otherwise isolated animal quarters. After only 14 feeding trials, the rats showed a marked decrease in corticosterone levels within 10 min of the experimenter's entrance whether fed and watered or not. The acquisition of this decrease was then examined over training trials and by comparing the conditioned animals (Group CD) with a group designed to control for pseudoconditioning, sensitization, and habituation (Group PC) during the use of the more distinctive conditioning stimulus of placing the rat's cage in a sound-attenuating chamber. During training. Group CD was fed .5-6 min after placement in the chamber, and Group PC was fed 1.5-2.5 hr before or after placement. After one training trial, the CD and PC groups showed an increase in corticosterone levels in response to chamber placement when not fed or watered. However, after 14 training trials the CD group exhibited a significant decline, whereas the PC group exhibited a rise in corticosterone levels. The results indicate that external stimuli can cause a decrease in corticosterone level by virtue of prior association with feeding and drinking. This strongly suggests an acquired inhibition of the pituitary-adrenal system.
本研究考察了刺激诱导的大鼠血浆皮质酮水平降低的性质。对大鼠采用23小时食物和水剥夺方案，每天早晨实验者一进入原本隔离的动物饲养区，就立即给大鼠喂食。仅经过14次喂食试验后，无论是否给大鼠喂食和供水，在实验者进入后的10分钟内，大鼠的皮质酮水平都显著下降。然后通过训练试验，并将条件反射组（CD组）与另一组（PC组）进行比较，来研究这种下降现象的习得情况。PC组是在使用将大鼠笼子置于隔音室这种更具特异性的条件刺激时，用于控制伪条件反射、敏感化和习惯化的对照组。在训练过程中，CD组在放入隔音室后0.5 - 6分钟喂食，PC组在放入隔音室前或后1.5 - 2.5小时喂食。经过一次训练试验，当不给CD组和PC组喂食和供水时，它们对放入隔音室的反应是皮质酮水平升高。然而，经过14次训练试验后，CD组的皮质酮水平显著下降，而PC组的皮质酮水平则升高。结果表明，外部刺激可凭借与进食和饮水的先前关联导致皮质酮水平降低。这强烈提示垂体 - 肾上腺系统存在习得性抑制。
