Behavioral and Cellular Modulation of l-DOPA-Induced Dyskinesia by β-Adrenoceptor Blockade in the 6-Hydroxydopamine-Lesioned Rat

Chronic dopamine replacement therapy in Parkinson's disease (PD) leads to deleterious motor sequelae known as l-DOPA-induced dyskinesia (LID). No known therapeutic can eliminate LID, but preliminary evidence suggests that dl-1-isopropylamino-3-(1-naphthyloxy)-2-propanol [(±)propranolol], a nonselective β-adrenergic receptor (βAR) antagonist, may reduce LID. The present study used the rat unilateral 6-hydroxydopamine model of PD to characterize and localize the efficacy of (±)propranolol as an adjunct to therapy with l-DOPA. We first determined whether (±)propranolol was capable of reducing the development and expression of LID without impairing motor performance ON and OFF l-DOPA. Coincident to this investigation, we used reverse-transcription polymerase chain reaction techniques to analyze the effects of chronic (±)propranolol on markers of striatal activity known to be involved in LID. To determine whether (±)propranolol reduces LID through βAR blockade, we subsequently examined each enantiomer separately because only the (−)enantiomer has significant βAR affinity. We next investigated the effects of a localized striatal βAR blockade on LID by cannulating the region and microinfusing (±)propranolol before systemic l-DOPA injections. Results showed that a dose range of (±)propranolol reduced LID without deleteriously affecting motor activity. Pharmacologically, only (−)propranolol had anti-LID properties indicating βAR-specific effects. Aberrant striatal signaling associated with LID was normalized with (±)propranolol cotreatment, and intrastriatal (±)propranolol was acutely able to reduce LID. This research confirms previous work suggesting that (±)propranolol reduces LID through βAR antagonism and presents novel evidence indicating a potential striatal locus of pharmacological action

Decreased noradrenaline transporter density in the motor cortex of Parkinson's disease patients

Reduced noradrenaline levels have been reported to occur in the motor cortices of PD patients postmortem. Imaging techniques have recently become available to specifically study noradrenergic terminal function in vivo using PET. The objective of this study was to evaluate cortical 11 C-MeNER binding in PD patients. Thirty PD patients and 12 healthy control subjects comparable in age, sex, and cognitive performance underwent PET imaging with 11 C-MeNER, a specific ligand of the noradrenaline transporter. Cortical noradrenaline transporter binding was compared at a voxel level using Statistical Parametric Mapping, whereas cortical thickness was assessed using FreeSurfer software with MRI. PD patients showed reduced 11 C-MeNER binding in the primary motor cortex unrelated to cortical thickness; other cortical regions did not differ between groups. In a subgroup analysis, patients with higher Hoehn & Yahr stage exhibited more pronounced 11 C-MeNER binding reductions. Loss of cortical noradrenergic projections to the primary motor cortex occurs in PD associated with disease stage. © 2018 International Parkinson and Movement Disorder Society