Cognitive Effects of Three ß-Adrenoceptor Acting Drugs in Healthy Volunteers and Patients with Parkinson’s Disease

Background: Noradrenergic signaling declines in Parkinson’s disease (PD) following locus coeruleus neurodegeneration. Epidemiologic studies demonstrate that ß-acting drugs slow PD progression.Objective: The primary objective was to compare the safety and effects of 3 ß-adrenoceptor (ß-AR) acting drugs on central nervous system (CNS) function after a single dose in healthy volunteers (HVs) and evaluate the effects of multiple doses of ß-AR acting drugs in HVs and PD-patients.Methods: In Part A, HVs received single doses of 32?mg salbutamol, 160µg clenbuterol, 60?mg pindolol and placebo administered in a randomized, 4-way cross-over study. In Part B (randomized cross-over) and Part C (parallel, 2:1 randomized), placebo and/or clenbuterol (20µg on Day 1, 40µg on Day 2, 80µg on Days 3–7) were administered. CNS functions were assessed using the NeuroCart test battery, including pupillometry, adaptive tracking and recall tests.Results: Twenty-seven HVs and 12 PD-patients completed the study. Clenbuterol improved and pindolol reduced the adaptive tracking and immediate verbal recall performance. Clenbuterol and salbutamol increased and pindolol decreased pupil-to-iris ratios. Clenbuterol was selected for Parts B and C. In Part B, clenbuterol significantly increased performance in adaptive tracking with a tendency toward improved performance in immediate and delayed verbal recall. In Part C trends toward improved performance in immediate and delayed verbal recall were observed in PD-patients. Typical cardiovascular peripheral ß2-AR effects were observed with clenbuterol.Conclusions: This study demonstrates the pro-cognitive effects of clenbuterol in HVs with similar trends in PD-patients. The mechanism of action is likely activation of ß2-ARs in the CNS.