Adopting the Rumsfeld approach to understanding the action of levodopa and apomorphine in Parkinson's disease.

"Author contributions: PJ: received honoraria for consultancies, advisory boards and sponsored lectures from Abbvie, Britannia Pharmaceuticals, Eisai, FP Pharmaceuticals, Kyowa Kirin, Hoffman La Roche, Profile Pharma, Tabuk Pharmaceuticals, UCB, Worldwide Clinical Trials and Zambon, outside of the submitted work. CFP: received royalties from Elsevier, Springer Verlag, honoraria from Abbvie, International Parkinson Disease and Movement Disorders Society, outside of the submitted work. VL: received grants from Parkinson’s UK and honoraria for sponsored symposium from UCB, Bial, Invisio, Profile, AbbVie, and Britannia Pharmaceuticals, outside of the submitted work. MV: received honoraria for scientific advisory boards and received research support and travel grants from Medtronic, Abbvie, Biogen, Sanofi, Britannia, Aguettant, Adelia, Elivie, LVL, Orkyn, outside of the submitted work. MA: received travel grants, speakers and consultancy honoraria and/or research grants from France Parkinson, Plateforme Nationale pour la Recherche sur la Fin de Vie, Institut des Neurosciences Cliniques de Rennes, Aguettant, Britannia Pharmaceutical Ltd, Adelia Medical, Linde Homecare, Homeperf, Asdia, France Développement Electronique and Society for Dental Science, outside of the submitted work. RB: has received consultancy and/or honoraria/lecture fees from Abbott, Britannia, Ipsen, Eisai, Novartis, Teva-Lundbeck, Takeda, and Otsuka pharmaceuticals, outside of the submitted work. DW: has received travel grants, speakers and consultancy honoraria and research grants from Abbvie, Abbott, Bial, Boston Scientific, Medtronic, Kyowa Kirin, Stadapharm outside of the submitted work. FB: has received travel grants, speakers and consultancy honoraria and research grants from Abbvie, Britannia, NovoNordisk, Pfizer, Stadapharm outside of the submitted work. WHJ: received honoraria for consultancies, advisory boards or sponsored lectures from Abbvie, Bial, Britannia Pharmaceuticals, Merz-Pharma, Stada, UCB, and Zambon, outside of the submitted work."

"This paper is based on a presentation given at a meeting supported by Britannia Pharmaceuticals at which all of the authors were present."