Levodopa up-regulates platelet alpha 2-adrenoceptors.
Treatment of dogs for 21 days with oral levodopa (100 mg b.i.d.) plus benserazide (25 mg b.i.d.) induced a significant increase in the number of platelet alpha 2-adrenoceptors labelled by [3H] yohimbine with no change in Kd. The rise was maximal at the end of the treatment and remained significant during the month following the cessation of treatment. Plasma catecholamine levels did not vary. Competition experiments showed a low affinity of both dopamine and levodopa for platelet alpha 2-adrenoceptors. These results suggest that levodopa treatment regulates alpha 2-adrenoceptor number in dog platelets.
Durrieu
G
G
Laboratoire de Pharmacologie Médicale et Clinique, INSERM U 317, Faculté de Médecine, Toulouse, France.
Valet
P
P
Berlan
M
M
Villeneuve
A
A
Montastruc
J L
JL
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002395:Catecholamines / Q000097:blood; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004285:Dogs; D004298:Dopamine / Q000494:pharmacology; D005260:Female; D007980:Levodopa / Q000494:pharmacology*; D008297:Male; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D015854:Up-Regulation / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D002395:Catecholamines; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D007980:Levodopa; D004298:Dopamine