Parkinson’s disease is a neurodegenerative disease with motor and non-motor symptoms. In Parkinson’s disease, a neurotransmitter imbalance occurs in the extrapyramidal system with a dopamine and GABA deficiency and an acetylcholine and glutamate surplus. Other classical neurotransmitters such as serotonin, the neuroactive substance adenosine and neuropeptides such as dynorphin and substance P are also involved in the pathophysiology of the disease. Here, we describe the alterations of the involved neuroactive substances and the relationships between them in the extrapyramidal system. From the findings previously reported in the literature, here a neural network is developed in the extrapyramidal system.