( ( ( Receptor sites ) ( -LRB- ( ( dopamine doorways ) -RRB- ) ) ) ( ( ( open up ) ( to ( ( ( receive ( the chemical ) ) and ) ( ( cause ( ( that ( pleasure part ) ) ( of ( your brain ) ) ) ) ( to fire ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Receptor) (NNS sites)) (PRN (-LRB- -LRB-) (NP (JJ dopamine) (NNS doorways)) (-RRB- -RRB-))) (VP (VBP open) (PRT (RP up)) (S (VP (TO to) (VP (VP (VB receive) (NP (DT the) (NN chemical))) (CC and) (VP (VB cause) (NP (NP (DT that) (NN pleasure) (NN part)) (PP (IN of) (NP (PRP$ your) (NN brain)))) (PP (TO to) (NP (NN fire)))))))) (. .)))
Receptor sites (dopamine doorways) open up to receive the chemical and cause that pleasure part of your brain to fire.
(ROOT (S (NP (NNP Addiction)) (VP (VBZ affects) (NP (NP (DT the) (JJ dopamine) (NNS receptors)) (PP (IN within) (NP (DT the) (NN brain))))) (. .)))