α-synuclein have been linked to familial PD. Further research is needed to clarify the extent to which these proteins modulate the trafficking of VMATs, and whether they may be exploited in order to gather more information about the exact mechanism of how disorders such as PD occurs, and how they may potentially be treated. Studies have shown that at the synaptic membrane, enzymes responsible for the synthesis of dopamine, tyrosine hydroxylase and amino acid aromatic decarboxylase are physically and functionally coupled with VMAT2. It was initially thought that the synthesis of these substances and the subsequent packaging of them into vesicles were two entirely separate processes. Animal research Current research related to VMAT uses VMAT2 knockout mice to explore the behavioral genetics of this transporter in an animal model. VMAT2 knockouts are known to be lethal as homozygotes, but heterozygote knockouts are not lethal and are used in many studies as a durable animal model. From knockout and knockdown mice, researchers have discovered that it is good to have over-expression or under-expression of the VMAT genes in some circumstances. Mice are also used in drug studies, particularity studies involving the effect cocaine and methamphetamine have on VMATs. Studies involving animals have prompted scientists to work on developing drugs that inhibit or enhance the function of VMATs. Drugs that inhibit VMATs may have use in addiction but further studies are needed. Enhancing the function of VMATs may also have therapeutic value. References External links Further reading Neurochemistry Signal transduction Receptors Neurotransmitter transporters Biogenic amines Integral membrane proteins VMAT inhibitors Amphetamine