Nondopaminergic mechanisms in levodopa-induced dyskinesia

• Published in: Movement disorders 2005-08, Vol.20 (8), p.919-931
• Main Author: Brotchie, Jonathan M.
• Format: Article
• Language: English
• Subjects: Animals; Antiparkinson Agents - adverse effects; basal ganglia circuitry; Biogenic Monoamines - classification; Biogenic Monoamines - metabolism; Biological and medical sciences; Brain - cytology; Brain - drug effects; Brain - metabolism; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Disease Models, Animal; Dopamine - metabolism; Drug toxicity and drugs side effects treatment; Dyskinesia, Drug-Induced - metabolism; Dyskinesia, Drug-Induced - physiopathology; globus pallidus; Humans; Levodopa - adverse effects; levodopa-induced dyskinesia; Medical sciences; Neurology; Parkinson Disease - drug therapy; Parkinson Disease - metabolism; Parkinson Disease - physiopathology; Pharmacology. Drug treatments; postsynaptic signaling; subthalamic nucleus; Synaptic Transmission - physiology; Toxicity: nervous system and muscle
• ISSN: 0885-3185; 1531-8257
• DOI: 10.1002/mds.20612

It has become increasingly apparent that Parkinson's disease involves many transmitter systems other than dopamine. This nondopaminergic involvement impacts on the generation of symptoms, on the neurodegenerative process, but, most tellingly, in the generation of side effects of current treatments, in particular, levodopa‐induced dyskinesia (LID). Such mechanisms contribute not only to the expression of LID once it has been established but also to the mechanisms responsible for the development, or priming, of the dyskinetic state and the subsequent maintenance of the brain in that primed state. Within the basal ganglia, abnormalities in different nondopaminergic components of the circuitry have been defined in LID. In particular, a role for enhanced inhibition of basal ganglia outputs by the GABAergic direct pathway has been suggested as a basic mechanism generating LID. We speculate that the external globus pallidus and subthalamic nucleus may play distinct roles in different forms of dyskinesia, e.g., chorea/dystonia; peak/diphasic/off. At the cellular level, an appreciation of abnormal signaling by, among others, glutamatergic (NMDA and AMPA receptors in particular), α2 adrenergic, serotonergic (5HT), cannabinoid and opioid mechanisms in both priming and expression of LID has begun to emerge over the last decade. This is being consolidated, though in many cases questions remain regarding the specific sites of such abnormality within the circuitry. Very recently, at the molecular level, mechanisms controlling neurotransmitter release and impacting on the ability of neurons to maintain particular forms of firing patterning and synchronization, e.g., SV2A, have been identified. This increased understanding has already delivered and will continue to define novel approaches to treatment that target both pre‐ and postsynaptic signaling molecules throughout the basal ganglia circuitry. © 2005 Movement Disorder Society