A study of dopaminergic sensitivity in Parkinson's disease: comparison in "de novo" and levodopa-treated patients.
The present study investigates dopaminergic sensitivity in Parkinson's disease (PD) through the measurement of neuroendocrine (growth hormone: GH, prolactin: PRL) and cardiovascular (blood pressure: BP, heart rate: HR) responses to low doses of apomorphine (5 micrograms/kg s.c.) in three groups of subjects: 13 normal volunteers (controls), 19 "de novo" never-treated PD patients, and 14 levodopa-treated PD patients. Apomorphine did not change BP and HR but significantly decreased PRL plasma levels in controls as well as in the two groups of PD patients. GH plasma levels significantly increased after apomorphine. There was no significant difference in the changes in neuroendocrine (GH, PRL) parameters in the two groups of PD patients in comparison with controls. However, "de novo" patients exhibited a significantly higher number of apomorphine-induced orthostatic symptoms (7 of 19) than did controls (0 of 13) or treated PD patients (2 of 14). These results show that hypothalamic dopaminergic sensitivity (studied through GH and PRL responses to apomorphine) is normal in PD. In contrast, because apomorphine-induced orthostatic hypotension is mainly due to the stimulation of peripheral dopaminergic receptors, our study suggests a peripheral dopaminergic hypersensitivity in some "de novo" never treated (but not in treated) PD patients.
Laboratorie de Pharmacologie Médicale et Clinique, INSERM U317, Faculté de Médecine, Toulouse, France.
M E
ME
Llau
G
G
Durrieu
M A
MA
Tran
J M
JM
Senard
O
O
Rascol
J L
JL
Montastruc
D000328:Adult; D000368:Aged; D000978:Antiparkinson Agents / Q000627:therapeutic use*; D001058:Apomorphine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004298:Dopamine / Q000502:physiology*; D004837:Epinephrine / Q000097:blood; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects / Q000503:physiopathology; D007980:Levodopa / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010300:Parkinson Disease / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology*; D017933:Peripheral Nervous System / Q000187:drug effects / Q000503:physiopathology; D011388:Prolactin / Q000097:blood; D012680:Sensitivity and Specificity
D000978:Antiparkinson Agents; D019382:Human Growth Hormone; D007980:Levodopa; D011388:Prolactin; D001058:Apomorphine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine