Adrenergic supersensitivity in parkinsonians with orthostatic hypotension.
The adrenergic status was studied through evaluation of platelet alpha 2-adrenoceptor number [( 3H]yohimbine binding sites), plasma catecholamine levels and blood pressure response to noradrenaline infusion in three groups of subjects (1) Parkinsonians with orthostatic hypotension; (2) Parkinsonians without orthostatic hypotension; and (3) control subjects. In Parkinsonians with orthostatic hypotension, systolic and diastolic blood pressures significantly (P less than 0.05) decreased from 144 +/- 9 and 76 +/- 6 mmHg in the lying position to 95 +/- 12 and 60 +/- 7 mmHg after 5 min standing. In these patients, noradrenaline plasma levels were significantly low (62 +/- 11 pg ml-1, (P less than 0.05) when compared with controls (219 +/- 13 pg ml-1) whereas no difference was noticed in Parkinsonians without orthostatic hypotension (195 +/- 14 pg ml-1). The noradrenaline dose required for a 25 mmHg increase in systolic blood pressure was significantly (P less than 0.01) lower in Parkinsonians with orthostatic hypotension (0.19 +/- 0.03 microgram kg-1) when compared with Parkinsonians without orthostatic hypotension (0.86 +/- 0.11 microgram kg-1) or with controls (0.68 +/- 0.1 microgram kg-1). Platelet alpha 2-adrenoceptor number was higher in Parkinsonians with orthostatic hypotension (313 +/- 52 fmol mg-1 protein) than in Parkinsonians without orthostatic hypotension (168 +/- 9 fmol mg-1 protein) or in controls (175 +/- 4 fmol mg-1 protein) with no change in Kd. This study demonstrates that in patients with Parkinson's disease, orthostatic hypotension is associated with an increase in both vascular sensitivity to noradrenaline and platelet alpha 2-adrenoceptor number.(ABSTRACT TRUNCATED AT 250 WORDS)
Senard
J M
JM
Laboratoire de Pharmacologie Medicale et Clinique, Faculte de Medicine, Centre Hospitalier Universitaire, Toulouse, France.
Valet
P
P
Durrieu
G
G
Berlan
M
M
Tran
M A
MA
Montastruc
J L
JL
Rascol
A
A
Montastruc
P
P
D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology; D001792:Blood Platelets / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D004837:Epinephrine / Q000097:blood; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000008:administration & dosage / Q000097:blood; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D015016:Yohimbine / Q000378:metabolism
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D009638:Norepinephrine; D004837:Epinephrine