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Adrenergic supersensitivity in Parkinsonians with orthostatic hypotension
Author(s) -
SENARD J. M.,
VALET P.,
DURRIEU G.,
BERLAN M.,
TRAN M. A.,
MONTASTRUC J. L.,
RASCOL A.,
MONTASTRUC P.
Publication year - 1990
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1990.tb01909.x
Subject(s) - orthostatic vital signs , blood pressure , medicine , anesthesia , endocrinology
. The adrenergic status was studied through evaluation of platelet α 2 ‐adrenoceptor number ([ 3 H]‐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 < 0.05) decreased from 144 pM 9 and 76 pM 6 mmHg in the lying position to 95 pM 12 and 60 pM 7 mmHg after 5 min standing. In these patients, noradrenaline plasma levels were significantly low (62 pM 11 pg ml ‐1 , ( P < 0.05) when compared with controls (219 pM 13 pg ml ‐1 ) whereas no difference was noticed in Parkinsonians without orthostatic hypotension (195 pM 14 pg ml ‐1 ). The noradrenaline dose required for a 25 mmHg increase in systolic blood pressure was significantly ( P < 0.01) lower in Parkinsonians with orthostatic hypotension (019 pM 0.03 μg kg ‐1 ) when compared with Parkinsonians without orthostatic hypotension (0.86 pM 0.11 μg kg ‐1 ) or with controls (0.68 pM 0.l μg kg ‐1 ). Platelet x 2 ‐adrenoceptor number was higher in Parkinsonians with orthostatic hypotension (313 pM 52 fmol mg ‐1 protein) than in Parkinsonians without orthostatic hypotension (168 pM 9 fmol mg ‐1 protein) or in controls (175 pM 4 fmol mg ‐1 protein) with no change in K d . 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 α 2 ‐adrenoceptor number. These observations suggest the existence of an α‐adrenergic supersensitivity in response to the low levels of plasma noradrenaline.