Dyskinesias occur in response to saline and naltrexone alone after priming with combination of dopaminergic agents and naltrexone in the MPTP parkinsonian monkeys.
Storage of motor memory involves the basal ganglia and more precisely the striatum, which receives afferents from all regions of the cerebral cortex. In Parkinsonian (MPTP) monkeys, we observed an increase in the dyskinetic response to dopaminergic agents when combined with opioid antagonists (naloxone or naltrexone) while morphine, attenuated the dyskinetic response. An interesting phenomenon observed after several acute co-administrations of naltrexone with dopaminergic agents was the manifestation of dyskinesias even after the injection of saline or naltrexone alone. However, this phenomenon was not observed when morphine was used in the same conditions. These unexpected observations concerning the acquisition of dyskinesias with saline or naltrexone alone, reported for the first time, might suggest the implication of a learning phenomenon in the induction of levodopa-induced dyskinesias.
Samadi
Pershia
P
Centre de recherche en Neurosciences, Le Centre Hospitalier Universitaire de Québec, CHUL RC-9800, 2705 Boulevard Laurier, Quebec, Canada G1V4G2.
Grégoire
Laurent
L
Rouillard
Claude
C
Bédard
Paul J
PJ
D000818:Animals; D015259:Dopamine Agents / Q000008:administration & dosage / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004409:Dyskinesia, Drug-Induced / Q000503:physiopathology; D005260:Female; D008252:Macaca fascicularis; D009271:Naltrexone / Q000008:administration & dosage / Q000633:toxicity*; D020734:Parkinsonian Disorders / Q000139:chemically induced* / Q000503:physiopathology; D012965:Sodium Chloride / Q000008:administration & dosage / Q000633:toxicity*
D015259:Dopamine Agents; D004338:Drug Combinations; D012965:Sodium Chloride; D009271:Naltrexone