Coover G D, Murison R, Sundberg H, Jellestad F, Ursin H
Physiol Behav. 1984 Aug;33(2):179-84. doi: 10.1016/0031-9384(84)90097-0.
The plasma corticosterone levels of rats were examined prior to their morning meal on Days 1, 7 and 20 of a regimen of 1 hr access daily to food mash and water. The relationship between external cues and meal provision was varied by feeding some groups immediately upon room entry each morning, and others with a variable interval 90-min delay. On Day 1, corticosterone levels of the hungry rats were elevated around the time of light onset, and until 90 min following room entry. On Day 7, corticosterone levels increased in response to room entry in the delay-fed rats, but did not increase further in immediately fed rats. These results were interpreted as indicating that low, but nonzero, expectancy of meal availability elevates corticosterone levels. On Day 20, the immediately fed rats showed a dip in corticosterone levels after room entry, responding to cues highly predictive of imminent meal availability. Delay-fed rats no longer showed an elevation to room entry. The relationship between corticosterone level and meal expectancy is essentially curvilinear in the hungry rat. The corticosterone levels are high when there is uncertainty about whether food is coming or not, and low when there is a very high or very low probability that food is coming.
在一项每天有1小时获取食物糊和水的实验方案中，于第1天、第7天和第20天对大鼠早餐前的血浆皮质酮水平进行了检测。通过每天早晨一些组大鼠一进入房间就立即喂食，而其他组延迟90分钟（间隔时间可变）喂食，来改变外部线索与进食供应之间的关系。在第1天，饥饿大鼠的皮质酮水平在光照开始时及之后直至进入房间后90分钟都有所升高。在第7天，延迟喂食的大鼠的皮质酮水平在进入房间时升高，但立即喂食的大鼠则没有进一步升高。这些结果被解释为表明对进食可得性的低但非零预期会提高皮质酮水平。在第20天，立即喂食的大鼠在进入房间后皮质酮水平出现下降，这是对高度预示即将有食物可得的线索的反应。延迟喂食的大鼠对进入房间不再有皮质酮水平升高的反应。在饥饿大鼠中，皮质酮水平与进食预期之间的关系本质上是曲线的。当不确定食物是否会来时皮质酮水平较高，而当食物到来的可能性非常高或非常低时皮质酮水平较低。
