Muscarinic cholinergic mediation of the GH response to gamma-hydroxybutyric acid: neuroendocrine evidence in normal and parkinsonian subjects

We have recently reported that parkinsonian patients show a significant GH response to gamma-hydroxybutyric acid (GHB), but not to gamma-aminobutyric acid (GABA)-ergic drug administration. In order to establish whether muscar inic cholinergic receptors mediate the GH secretion induced by GHB? normal men and parkinsonian patients were tested with GHB both in the absence and in the presence of the anticholinergic agent, pirenzepine. Both normal cont rols and parkinsonian patients showed a significant serum GB rise in respon se to GHB (25 mg/kg body weight p.o.) even though a slightly, but significa ntly lower response was observed in parkinsonian patients. Pretreatment wit h pirenzepine (100 mg p.o. 2 h before GHB) completely suppressed the GHB-in duced GH release in both normal controls and parkinsonian patients. These d ata indicate that a cholinergic mechanism mediates the GH response to GHB i n normal men. In addition the data indicate that this pathway is preserved in the parkinsonian brain. (C) 2000 Elsevier Science Ltd. All rights reserv ed.