ior,andthenpresentsevidencethatisnotconsistentwiththathypothesis.Thethirdandfourthparagraphsreturntothenewerhypothesisintroducedinthefirstparagraphandprovide“evidenceandarguments”thatsupportthisalternativehypothesis.2.Disthebestanswer.Lines11-23statethatadenosine“depressesneuronfiring”bybindingtospecificreceptorsonneuronalmembranes,whichinturninhibitsthereleaseofneurotransmitters.Lines27-35describeSnyderetal’shypothesisaboutcaffeine.Theyproposethatcaffeinebindstospecificreceptorsonneuronalmembranes,whichpreventsadenosinefrombindingtothosereceptorsand“allowstheneuronstofiremorereadilythattheyotherwisewould”.Therefore,accordingtoSnyderetal,caffeinediffersfromadenosineinthatcaffeinepermitsneurotransmitterreleasewhenitisboundtoadenosinereceptors,whereasadenosineinhibitsneruotransmitterrelease.
全文预览
