Reviewed:

<bibtex>
    @MISC{ R-HSA-111885.4,
           author          = {Castagnoli, L},
           title           = {Opioid Signalling},
           crossref        = {Reactome:R-HSA-111885.4, DOI:10.3180/REACT_15295.1},
           howpublished    = {\url{http://www.reactome.org/PathwayBrowser/#R-HSA-111885.4}},
           note            = {Reactome Pathway Knowledgebase, http://www.reactome.org/},
           month           = {November},
           year            = {2008},
           }
</bibtex>