( ( When ( ( ( alpha 2 ) agonists ) ( ( bind ( to ( ( alpha 2 ) ( adrenoceptor sites ) ) ) ) ( on ( a ( peripheral ( or ( CNS neuron ) ) ) ) ) ) ) ) ( , ( they ( ( ( ( interrupt ( release ( of ( the ( neurotransmitter noradrenaline ) ) ) ) ) , ) ( thus ( interrupting ( nerve impulses ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (ADJP (NN alpha) (CD 2)) (NNS agonists)) (VP (VBD bind) (PP (TO to) (NP (ADJP (NN alpha) (CD 2)) (NN adrenoceptor) (NNS sites))) (PP (IN on) (NP (DT a) (JJ peripheral) (CC or) (NN CNS) (NN neuron)))))) (, ,) (NP (PRP they)) (VP (VBD interrupt) (NP (NP (NN release)) (PP (IN of) (NP (DT the) (NN neurotransmitter) (NN noradrenaline)))) (, ,) (S (ADVP (RB thus)) (VP (VBG interrupting) (NP (NN nerve) (NNS impulses))))) (. .)))
When alpha 2 agonists bind to alpha 2 adrenoceptor sites on a peripheral or CNS neuron, they interrupt release of the neurotransmitter noradrenaline, thus interrupting nerve impulses.
(ROOT (S (PP (IN Like) (S (NP (DT a) (NN runner)) (VP (VBG passing) (NP (DT a) (NN baton))))) (, ,) (NP (NP (DT the) (NN transmission)) (PP (IN of) (NP (NP (NN nerve) (NNS impulses)) (PP (IN between) (NP (NNS neurons)))))) (VP (VBZ depends) (PP (IN on) (NP (NNS neurotransmitters)))) (. .)))