title: Effect of enhancement of cholinergic tone on the growth hormone response to acute hyperglycaemia or thyrotropin-releasing hormone in dogs.
abstract: The effect of enhancement of cholinergic tone by pyridostigmine on the growth hormone (GH) response to thyrotropin-releasing hormone (TRH) or glucose-induced acute hyperglycaemia was tested in six adult unanaesthetized beagle dogs. Both TRH (5μg/ kg iv) and glucose (2 g/kg orally) did not significantly alter baseline GH levels but reduced the GH response to GH-releasing hormone (GHRH) (2 μg/kg iv), although this effect was more clear-cut with TRH than with glucose. Pretreatment with pyridostigmine (2 mg/kg orally) counteracted the inhibitory effect of hyperglycaemia on the GHRH-induced GH release, but had no effect on the inhibition induced by TRH. In summary, these results indicate that: 1) acute hyperglycaemia and TRH play an inhibitory role on GHRH-stimulated GH secretion in dogs; 2) the inhibitory effect of acute hyperglycaemia is mediated via hypothalamic cholinergic neurotransmission, whereas other neurotransmitter pathways would be. involved in the effect of TRH.
authors.affiliation: Department of Pharmacology, Chemotherapy and Toxicology, University of Milan, 20129 Milan, Italy.
authors.forename: V M
authors.initials: VM
authors.lastname: Arce
authors.forename: S G
authors.initials: SG
authors.lastname: Cella
authors.forename: V
authors.initials: V
authors.lastname: Locatelli
authors.forename: E E
authors.initials: EE
authors.lastname: Müller