Raclopride
Raclopride is a typical antipsychotic. It acts as a selective antagonist on D dopamine receptors. It has been used in trials studying Parkinson Disease. Its selectivity to the cerebral D receptors is characterized by its respective K-values, which are as follows: 1.8, 3.5, 2400 and 18000 nM for D, D, D and D receptors respectively. It can be radiolabelled with radioisotopes, e.g. H or C and used as a tracer for "in vitro" imaging (autoradiography) as well as "in vivo" imaging positron emission tomography (PET). Images obtained by cerebral PET scanning (e.g. PET/CT or PET/MRI) allow  the non-invasive assessment of the binding capacity of the cerebral D dopamine receptor, which can be useful for the diagnosis of movement disorders. In particular, cerebral D receptor binding as measured by carbon-11-raclopride (C-raclopride) has shown to reflect disease severity of Huntington's disease, a genetic disease characterized by selective degeneration of cerebral D receptors. Other studies have investigated the relationship of D receptor binding capacity and personality disorders. One study found decreased binding in the "detachment" personality trait. Radiolabelled raclopride is also commonly used to determine the efficacy and neurotoxicity of dopaminergic drugs.