The invention relates to nematodes as model organisms for the investigation of neurodegenerative diseases in particular. Parkinsons disease, uses and methods for the discovery of substances and genes which can be used in the treatment of the above disease states and identification of a nematode gene, from C. elegans, which is homologous to the human parkin gene associated with Parkinsons disease. The invention further relates to those nematodes which contain an aberrant or missing expression of at least one gene, preferably a parkin gene and/or a .alpha.-synuclein gene, which is connected with Parkinsons disease. According to the invention, the above organisms can be used for the identification and characterisation of medicaments for the treatment of said disease states.