( ( These drugs ) ( ( block ( receptors ( for ( the ( brain ( chemical dopamine ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS drugs)) (VP (VBP block) (NP (NP (NNS receptors)) (PP (IN for) (NP (DT the) (NN brain) (NN chemical) (NN dopamine))))) (. .)))
These drugs block receptors for the brain chemical dopamine.
(ROOT (S (NP (NNP Addiction)) (VP (VBZ affects) (NP (NP (DT the) (JJ dopamine) (NNS receptors)) (PP (IN within) (NP (DT the) (NN brain))))) (. .)))