GRE Reading Comprehension: JiJing 352-GRE阅读机经352篇 - 2S2H_QEJ6UKNIEQ5K

When rats are placed under conditions of stress, their adrenal glands immediately increase production of the hormone corticosterone, and soon thereafter the rats' white blood cell count drops substantially. Yet rats without functioning adrenal glands experience little decrease in white blood cell count when placed under conditions of stress. It is likely, therefore, that an increase in corticosterone produced by a rat's adrenal glands causes the rat's white blood cell count to decrease.