title: The selective kappa-opioid receptor agonist U50,488 reduces L-dopa-induced dyskinesias but worsens parkinsonism in MPTP-treated primates.
abstract: Several lines of evidence demonstrate that the striatal enkephalinergic system may be involved in the development of LIDs. Preproenkephalin-B (PPE-B) transcript levels are elevated with LIDs and there are also declines in kappa-opioid and other opioid receptors in different regions of the basal ganglia. If reduced kappa-opioid receptors are linked to LIDs, it is possible that drugs that stimulate this subtype may decrease dyskinesias. We therefore initiated experiments to investigate the effect of kappa-opioid receptor activation on LIDs. We first tested the selective kappa-agonist U50,488 in rats with unilateral lesions of the nigrostriatal pathway. Chronic L-dopa treatment induced abnormal involuntary movements, including axial, orolingual and forelimb dyskinesias contralateral to the lesion. U50,488 administration prior to L-dopa treatment reduced these movements by 70%, suggesting that U50,488 has potential as an anti-dyskinetic treatment. We next tested its effect in a parkinsonian nonhuman primate model, which offers the advantage that parkinsonism and LIDs can clearly be differentiated and that the dyskinesias are similar to those in parkinsonian patients. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys were treated with L-dopa (5 mg/kg p.o.) twice daily for 3 weeks to induce dyskinesias. As in the rodent model, U50,488 (0.1-1.0 mg/kg i.m.) decreased LIDs in a dose-dependent fashion. However, the anti-parkinsonian effect of L-dopa was similarly reduced, and side effects developed, including sedation and vomiting. These data suggest that kappa-opioid agonists such as U50,488 may not be clinically useful antidyskinetic agents because they also reverse the anti-parkinsonian effect of l-dopa.
authors.affiliation: The Parkinson's Institute, 1170 Morse Avenue, Sunnyvale, CA 94089, USA.
authors.forename: Heather
authors.initials: H
authors.lastname: Cox
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Togasaki
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: J William
authors.initials: JW
authors.lastname: Langston
authors.forename: Donato A
authors.initials: DA
authors.lastname: Di Monte
authors.forename: Maryka
authors.initials: M
authors.lastname: Quik
mesh_terms: D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000978:Antiparkinson Agents / Q000037:antagonists & inhibitors; D015259:Dopamine Agents; D004305:Dose-Response Relationship, Drug; D004409:Dyskinesia, Drug-Induced / Q000503:physiopathology*; D005260:Female; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D007980:Levodopa / Q000037:antagonists & inhibitors; D008297:Male; D020734:Parkinsonian Disorders / Q000139:chemically induced* / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000819:agonists*; D012453:Saimiri; D014839:Vomiting / Q000139:chemically induced
chemical_list: D000978:Antiparkinson Agents; D015259:Dopamine Agents; D006993:Hypnotics and Sedatives; D017473:Receptors, Opioid, kappa; D007980:Levodopa; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine