Defective 5-HT 1-receptor-mediated neurotransmission in the control of growth hormone secretion in Parkinson's disease.
In order to gain a better insight in the serotonergic disorder affecting the parkinsonian brain, the growth hormone (GH) response to the 5-HT 1 serotonergic receptor agonist sumatriptan was tested. Sumatriptan was injected subcutaneously in 10 de novo parkinsonian patients (aged 58-69 years) and in 9 age-matched normal controls. On different occasions, subjects were also tested with GH-releasing hormone (GH-RH; 1 micrograms/kg body weight in an intravenous bolus) and L-arginine (30 g in 50 ml normal saline over 30 min), which releases GH from somatostatin inhibition, to determine whether GH secretion in response to alternate secretagogues is preserved in Parkinson's disease. In addition, a control test with the administration of normal saline instead of drug treatments was performed. Plasma GH levels were recorded over 2 h in all tests. Placebo administration did not change plasma GH levels in any subject. Similar GH responses were observed in normal controls and parkinsonian patients when GH-RH or arginine were administered. A significant GH increase was observed in normal controls after sumatriptan injection; in contrast, GH secretion was not modified by sumatriptan administration in parkinsonian patients. These data show that Parkinson's disease is associated with an impairment in the 5-HT1-receptor-mediated serotonergic transmission in the control of GH secretion, suggesting that this specific defect might alter other serotonergic-mediated mechanisms in the parkinsonian brain.
Volpi
R
R
Department of Internal Medicine, University of Parma, Italy.
Caffarra
P
P
Scaglioni
A
A
Boni
S
S
Saginario
A
A
Chiodera
P
P
Coiro
V
V
D000368:Aged; D000704:Analysis of Variance; D001120:Arginine; D016022:Case-Control Studies; D013007:Growth Hormone-Releasing Hormone; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D010902:Pituitary Gland / Q000503:physiopathology*; D017366:Serotonin Receptor Agonists; D018170:Sumatriptan
D017366:Serotonin Receptor Agonists; D019382:Human Growth Hormone; D018170:Sumatriptan; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine