title: Endogenous glucagon-like peptide-1 reduces drinking behavior and is differentially engaged by water and food intakes in rats.
abstract: Glucagon-like peptide-1 (GLP-1) is produced in the ileum and the nucleus of the solitary tract. It is well known that GLP-1 controls food intake, but there is a growing literature indicating that GLP-1 also is involved in fluid intake. It is not known, however, if the observed effects are pharmacological or if endogenous GLP-1 and its receptor contribute to physiological fluid intake control. Accordingly, we blocked endogenous GLP-1 by application of a receptor antagonist and measured subsequent drinking. Furthermore, we measured changes in GLP-1-associated gene expression after water intake, and compared the effects of fluid intake to those caused by food intake. Rats injected with the antagonist exendin-9 (Ex-9) drank more fluid in response to either subcutaneous hypertonic saline or water deprivation with partial rehydration than did vehicle-treated rats. Analysis of licking behavior showed that Ex-9 increased fluid intake by increasing the number of licking bursts, without having an effect on the number of licks per burst, suggesting that endogenous GLP-1 suppresses fluid intake by influencing satiety. Subsequent experiments showed that water intake had a selective effect on central GLP-1-related gene expression, unlike food intake, which affected both central and peripheral GLP-1. Although water and food intakes both affected central GLP-1-relevant gene expression, there were notable differences in the timing of the effect. These results show a novel role of the endogenous GLP-1 system in fluid intake, and indicate that elements of the GLP-1 system can be engaged separately by different forms of ingestive behavior.
authors.affiliation: Behavioral Neuroscience Program, Department of Psychology, The State University of New York at Buffalo, Buffalo, New York.
authors.forename: Naomi J
authors.initials: NJ
authors.lastname: McKay
authors.affiliation: Behavioral Neuroscience Program, Department of Psychology, The State University of New York at Buffalo, Buffalo, New York.
authors.forename: Daniela L
authors.initials: DL
authors.lastname: Galante
authors.affiliation: Behavioral Neuroscience Program, Department of Psychology, The State University of New York at Buffalo, Buffalo, New York danielsd@buffalo.edu.
authors.forename: Derek
authors.identifier: http://orcid.org/0000-0003-3216-5128
authors.initials: D
authors.lastname: Daniels
mesh_terms: D000818:Animals; D004326:Drinking / Q000187:drug effects / Q000502:physiology*; D004327:Drinking Behavior / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D052216:Glucagon-Like Peptide 1 / Q000037:antagonists & inhibitors / Q000097:blood / Q000502:physiology*; D007082:Ileum / Q000378:metabolism; D007276:Injections, Intraventricular; D008297:Male; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology; D052336:Proglucagon / Q000097:blood / Q000378:metabolism / Q000502:physiology; D051381:Rats; D012462:Saline Solution, Hypertonic / Q000494:pharmacology; D017552:Solitary Nucleus / Q000187:drug effects / Q000378:metabolism; D014868:Water Deprivation / Q000502:physiology
chemical_list: D010446:Peptide Fragments; D012462:Saline Solution, Hypertonic; C083773:exendin (9-39); D052336:Proglucagon; D052216:Glucagon-Like Peptide 1
keywords: fluid homeostasis; food intake; glucagon-like peptide-1; thirst; water intake