title: Ghrelin enhances olfactory sensitivity and exploratory sniffing in rodents and humans.
abstract: Olfaction is an integral part of feeding providing predictive cues that anticipate ingestion. Although olfactory function is modulated by factors such as prolonged fasting, the underlying neural mechanisms remain poorly understood. We recently identified ghrelin receptors in olfactory circuits in the brain. We therefore investigated the role of the appetite-stimulating hormone ghrelin in olfactory processing in rodents and humans, testing the hypothesis that ghrelin lowers olfactory detection thresholds and enhances exploratory sniffing, both being related to food seeking. In rats, intracerebroventricular ghrelin decreased odor detection thresholds and increased sniffing frequency. In humans, systemic ghrelin infusions significantly enhanced sniff magnitudes in response to both food and nonfood odorants and air in comparison to control saline infusions but did not affect the pleasantness ratings of odors. This is consistent with a specific effect on odor detection and not the hedonic value of odors. Collectively, our findings indicate that ghrelin stimulates exploratory sniffing and increases olfactory sensitivity, presumably enhancing the ability to locate, identify, and select foods. This novel role is consistent with ghrelin's overall function as a signal amplifier at the molecular interface between environmental and nutritional cues and neuroendocrine circuits controlling energy homeostasis.
authors.affiliation: Division of Endocrinology, Diabetes, and Metabolism, Department of Internal Medicine, University of Cincinnati, Cincinnati, Ohio 45267, USA. jenny.tong@uc.edu
authors.forename: Jenny
authors.initials: J
authors.lastname: Tong
authors.forename: Erica
authors.initials: E
authors.lastname: Mannea
authors.forename: Pascaline
authors.initials: P
authors.lastname: Aimé
authors.forename: Paul T
authors.initials: PT
authors.lastname: Pfluger
authors.forename: Chun-Xia
authors.initials: CX
authors.lastname: Yi
authors.forename: Tamara R
authors.initials: TR
authors.lastname: Castaneda
authors.forename: Harold W
authors.initials: HW
authors.lastname: Davis
authors.forename: Xueying
authors.initials: X
authors.lastname: Ren
authors.forename: Sarah
authors.initials: S
authors.lastname: Pixley
authors.forename: Stephen
authors.initials: S
authors.lastname: Benoit
authors.forename: Karyne
authors.initials: K
authors.lastname: Julliard
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Woods
authors.forename: Tamas L
authors.initials: TL
authors.lastname: Horvath
authors.forename: Mark M
authors.initials: MM
authors.lastname: Sleeman
authors.forename: David
authors.initials: D
authors.lastname: D'Alessio
authors.forename: Silvana
authors.initials: S
authors.lastname: Obici
authors.forename: Robert
authors.initials: R
authors.lastname: Frank
authors.forename: Matthias H
authors.initials: MH
authors.lastname: Tschöp
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology; D019921:Biotinylation; D005106:Exploratory Behavior / Q000187:drug effects*; D005260:Female; D005502:Food; D054439:Ghrelin / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007763:Lac Operon / Q000235:genetics; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D051381:Rats; D020318:Rats, Long-Evans; D054440:Receptors, Ghrelin / Q000378:metabolism; D012903:Smell / Q000187:drug effects*; D055815:Young Adult
chemical_list: D054439:Ghrelin; D054440:Receptors, Ghrelin