BETA-ADRENERGIC SENSITIVITY IN PARKINSONS-DISEASE - EFFECT OF LEVODOPA TREATMENT

The β-adrenergic sensitivity in never-treated and levodopa-treated patients with Parkinson's disease (PD) was studied through the evaluation of lymphocyte β-adrenoceptor number ([125I]cyanopindolol binding sites) and chronotropic and metabolic (plasma nonesterified fatty acids - NEFA) responses to isoproterenol. No change was found in B(max) values or affinity constant K(d) between never-treated patients, levodopa-treated patients with PD, and controls. At rest, no difference was observed in heart rate, plasma catecholamine, or NEFA levels between the three groups. Isoproterenol sensitivity (chronotropic response and plasma NEFA increase) was similar in never-treated and treated PD. The results suggest that peripheral β-adrenergic sensitivity is unaffected either by the pathophysiological process of PD or by levodopa treatment.