Role of D1 and D2 receptors in the regulation of voluntary movements.
The effect of dopamine receptor agonist cabergoline on muscle tone and contractility was studied in healthy volunteers. Variations in muscle tone were evaluated by means of transcranial magnetic stimulation under resting conditions. Muscle contractility was estimated from kinematic parameters of voluntary movements. Oral administration of cabergoline in a dose of 2 mg was followed by a decrease in muscle tone and increase in muscle contractility. Our findings indicate that the brain dopaminergic system regulates voluntary movements by decreasing the tone and increasing contractility of skeletal muscles. Under resting conditions, prolonged exposure of D1 receptors to dopamine in a low concentration decreases excitability threshold of the motor cortex and reduces muscle tone. During voluntary movements, short-term stimulation of D2 receptors with dopamine in a high concentration increases excitability of the motor cortex and induces muscle contraction. The movement occurs when D2 receptor-mediated excitation of the cortex and induced muscle contraction exceed the decrease in muscle tone and excitability threshold caused by stimulation of D1 receptors.
Korchounov
A M
AM
Center for Locomotor Disorders, Bad Nauheim/Frankfurt am Main, Germany. korchounov@yahoo.de
D000328:Adult; D001921:Brain / Q000378:metabolism; D000077465:Cabergoline; D018491:Dopamine Agonists / Q000494:pharmacology; D004873:Ergolines / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009129:Muscle Tonus / Q000187:drug effects / Q000502:physiology*; D017447:Receptors, Dopamine D1 / Q000378:metabolism*; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D055815:Young Adult
D018491:Dopamine Agonists; D004873:Ergolines; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D000077465:Cabergoline