ABSTRACT
L-dopa (l-3,4-dihydroxyphenylalanine)-induced dyskinesia (LID) is a debilitating complication of dopamine replacement therapy for Parkinson's disease. The potential contribution of striatal D2 receptor (D2R)-positive neurons and downstream circuits in the pathophysiology of LID remains unclear. In this study, we investigated the role of striatal D2R+ neurons and downstream globus pallidus externa (GPe) neurons in a rat model of LID. Intrastriatal administration of raclopride, a D2R antagonist, significantly inhibited dyskinetic behavior, while intrastriatal administration of pramipexole, a D2-like receptor agonist, yielded aggravation of dyskinesia in LID rats. Fiber photometry revealed the overinhibition of striatal D2R+ neurons and hyperactivity of downstream GPe neurons during the dyskinetic phase of LID rats. In contrast, the striatal D2R+ neurons showed intermittent synchronized overactivity in the decay phase of dyskinesia. Consistent with the above findings, optogenetic activation of striatal D2R+ neurons or their projections in the GPe was adequate to suppress most of the dyskinetic behaviors of LID rats. Our data demonstrate that the aberrant activity of striatal D2R+ neurons and downstream GPe neurons is a decisive mechanism mediating dyskinetic symptoms in LID rats.
Subject(s)
Rats , Animals , Levodopa/toxicity , Dopamine , Parkinsonian Disorders/drug therapy , Oxidopamine , Dyskinesia, Drug-Induced , Corpus Striatum/metabolism , Neurons/metabolism , Receptors, Dopamine D2/metabolism , Antiparkinson Agents/toxicityABSTRACT
Desde la introducción de la levodopa para el manejo de la enfermedad de Parkinson ésta ha sido el tratamiento estándar de esta enfermedad. La aparición de fármacos alternativos como los agonistas dopaminérgicos abrieron un debate acerca de los potenciales beneficios de estas terapias por sobre levodopa y los eventuales efectos deletéreos de esta última. En este artículo se actualiza la información acerca de las complicaciones motoras y de neurotoxicidad inducidas por levodopa.