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Although the hormone adrenaline is known to regulate memory storage, it does not pass from the blood into brain cells. We are faced with an apparent paradox: how can a hormone that does not act directly on the brain have such a large effect on brain function? Recently, we tested the possibility that one of the hormone's actions outside the brain might be responsible. Since one consequence of adrenaline release in an animal is an increase in blood glucose levels, we examined the effects of glucose on memory in rats. We found that glu-cose injected immediately after training enhances memory tested the next day. Additional evidence was provided by negative findings: drugs called adrenergic antagonists, which block peripheral adrenaline receptors, disrupted adrenaline's ability to regulate memory but did not affect memory enhancements produced by glucose that was not stimulated by adrenaline. These results are as they should be if adrenaline affects memory modulation by increasing blood glucose levels.
The primary purpose of the passage is to
A.reconcile two opposing theories
B.compare two different explanations for a phe-nomenon
C.describe experimental research that appears to support an unpopular theory
D.present evidence that may help to resolve an apparent contradiction
E.describe a hypothesis that has cause a controversy
It can be inferred from the passage that the author would most likely describe the "additional evidence" (line 12) provided by experiments with adrenergic antagonists as
A.revolutionary
B.disappointing
C.incomplete
D.unexpected
E.corroborative
The passage provides information about which of the following topics?
A.The mechanism by which glucose affects memory storage
B.The evidence that prompted scientist to test the effects of adrenaline on memory regulation
C.The reason that the effects of glucose on memory were tested
D.The ways that memory storage modifies the structure of the brain
E.The kinds of training used to test memory enhancement in rats
The author refers to the results of the experiment using adrenergic antagonists as "negative findings" (line 13) most likely because the adrenergic antagonists
A.failed to disrupt adrenaline's effect on memory
B.did not affect glucose's ability to enhance memory
C.did not block adrenaline's ability to increase blood glucose levels
D.only partially affected adrenaline's ability to enhance memory
E.disrupted both adrenaline's and glucose's effect on memory
