小安阅读第10篇有点疑问

cdstella

各位,我在做小安阅读第十篇的时候有点不明白,希望大家帮忙看一下.谢谢
文章第二段如下:
For many years, caffeine’s effects have beenattributed to its inhibition of the production of phosphodiesterase, an enzymethat breaks down the chemical called cyclic AMP. A number of neurotransmittersexert their effects by first increasing cyclic AMP concentrations in targetneurons. Therefore, prolonged periods at the elevated concentrations, as mightbe brought about by a phosphodiesterase inhibitor, could lead to a greateramount of neuron firing and, consequently, to behavioral stimulation. But Snyder et al point out thatthe caffeine concentrations needed to inhibit the production of phosphodiesterasein the brain are much higher than those that produce stimulation. Moreover,other compounds that block phosphodiesterase’s activity are not stimulants
我不理解最后一句的意思及表达意图,我认为咖啡因的刺激作用完全取决于它对抑制剂的抑制,它本身没有刺激的作用. 所以最后一句蒙了.......
谢谢

Apolloemma

Coffeine-->Phos - -->cyclic AMP + --> begavioral stimulation +


Therefore, prolonged periods at the elevated concentrations, as mightbe brought about by a phosphodiesterase inhibitor, could lead to a greateramount of neuron firing and, consequently, to behavioral stimulation.

这是 SEA 提反对以前的逻辑链

SEA 说 Coffeine 需要 抑制Phosphate的浓度比对行为刺激的浓度高，也就是否定了咖啡因通过印制