title: Stimulatory effect of ghrelin on food intake in bullfrog larvae.
abstract: Ghrelin is a potent orexigenic peptide implicated in appetite regulation in rodents. However, except for teleost fish, the involvement of ghrelin in the regulation of feeding in non-mammalian vertebrates has not been well studied. Anuran amphibian larvae feed and grow during the pre- and prometamorphic stages, but, thereafter they stop feeding as the metamorphic climax approaches. Therefore, orexigenic factors seem to play important roles in growing larvae. In the present study, we examined the effect of intraperitoneal (IP) or intracerebroventricular (ICV) administration of synthetic bullfrog ghrelin (n-octanoylated 28-amino acid form) on food intake in larvae at the prometamorphic stages. Cumulative food intake was significantly increased by IP (8 and 16pmol/g body weight (BW)) or ICV (0.5 and 1pmol/g BW) administration of ghrelin during a 15-min observation period. The orexigenic action of ghrelin at 8pmol/g BW (IP) or at 0.5pmol/g BW (ICV) was blocked by treatment with a growth hormone secretagogue-receptor antagonist, [D-Lys(3)]GHRP-6 at 80pmol/g BW (IP) or at 5pmol/g BW (ICV). We then investigated the effect of feeding status on expression levels of the ghrelin transcript in the hypothalamus and gastrointestinal tract. Ghrelin mRNA levels in both were decreased 15 and 60min after feeding. These results indicate that ghrelin acts as an orexigenic factor in bullfrog larvae.
authors.affiliation: Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Department of Biochemistry, National Cerebral and Cardiovascular Center (NCVC) Research Institute, Suita, Osaka 565-8565, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kaiya
authors.affiliation: Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan; Laboratory of Regulatory Biology, Graduate School of Innovative Life Science, University of Toyama, 3190-Gofuku, Toyama, Toyama 930-8555, Japan. Electronic address: kmatsuda@sci.u-toyama.ac.jp.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Matsuda
mesh_terms: D029845:Amphibian Proteins / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D019167:Appetite Stimulants / Q000008:administration & dosage*; D002149:Energy Intake / Q000187:drug effects*; D041981:Gastrointestinal Tract / Q000378:metabolism; D015870:Gene Expression; D054439:Ghrelin / Q000008:administration & dosage* / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D011892:Rana catesbeiana
chemical_list: D029845:Amphibian Proteins; D019167:Appetite Stimulants; D054439:Ghrelin
keywords: Bullfrog; Food intake; GHS receptor; GHS receptor antagonist; Ghrelin; Ghrelin mRNA; Orexigenic action; Prometamorphic larvae