( ( ( Previous research ) ( at Brookhaven ) ) ( ( has ( shown ( that ( ( addictive drugs ) ( ( increase ( ( the level ) ( of ( dopamine ( in ( the brain ) ) ) ) ) ) ( ( ( ( while ( ( the subject ) ( is intoxicated ) ) ) , ) and ) ( that ( addicts ( ( have ( fewer ( dopamine receptors ) ) ) ( than non-addicts ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Previous) (NN research)) (PP (IN at) (NP (NNP Brookhaven)))) (VP (VBZ has) (VP (VBN shown) (SBAR (IN that) (S (NP (JJ addictive) (NNS drugs)) (VP (VBP increase) (NP (NP (DT the) (NN level)) (PP (IN of) (NP (NP (NN dopamine)) (PP (IN in) (NP (DT the) (NN brain)))))) (SBAR (SBAR (IN while) (S (NP (DT the) (NN subject)) (VP (VBZ is) (ADJP (JJ intoxicated))))) (, ,) (CC and) (SBAR (IN that) (S (NP (NNS addicts)) (VP (VBP have) (NP (JJR fewer) (NN dopamine) (NNS receptors)) (PP (IN than) (NP (NNS non-addicts)))))))))))) (. .)))
Previous research at Brookhaven has shown that addictive drugs increase the level of dopamine in the brain while the subject is intoxicated, and that addicts have fewer dopamine receptors than non-addicts.
(ROOT (S (NP (NNP Addiction)) (VP (VBZ affects) (NP (NP (DT the) (JJ dopamine) (NNS receptors)) (PP (IN within) (NP (DT the) (NN brain))))) (. .)))