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Gonadotropin-releasing hormone 2 suppresses food intake in the zebrafish, Danio rerio.

Nishiguchi R, Azuma M, Yokobori E, Uchiyama M, Matsuda K - Front Endocrinol (Lausanne) (2012)

Bottom Line: ICV injection of GnRH2 at 0.1 and 1 pmol/g body weight (BW) induced a marked decrease of food consumption in a dose-dependent manner during 30 min after feeding.Levels of GnRH2 mRNA obtained from fish that had been provided excess food for 7 days were higher than those in fish that had been fed normally.These results suggest that, in zebrafish, GnRH2 acts as an anorexigenic factor, as is the case in goldfish.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama Toyama, Japan.

ABSTRACT
Gonadotropin-releasing hormone (GnRH) is an evolutionarily conserved neuropeptide with 10 amino acid residues, of which several structural variants exist. A molecular form known as GnRH2 ([His(5) Trp(7) Tyr(8)]GnRH, also known as chicken GnRH II) is widely distributed in vertebrates except for rodents, and has recently been implicated in the regulation of feeding behavior in goldfish. However, the influence of GnRH2 on feeding behavior in other fish has not yet been studied. In the present study, therefore, we investigated the role of GnRH2 in the regulation of feeding behavior in a zebrafish model, and examined its involvement in food intake after intracerebroventricular (ICV) administration. ICV injection of GnRH2 at 0.1 and 1 pmol/g body weight (BW) induced a marked decrease of food consumption in a dose-dependent manner during 30 min after feeding. Cumulative food intake was significantly decreased by ICV injection of GnRH2 at 1 pmol/g BW during the 30-min post-treatment observation period. The anorexigenic action of GnRH2 was completely blocked by treatment with the GnRH type I receptor antagonist Antide at 25 pmol/g BW. We also examined the effect of feeding condition on the expression level of the GnRH2 transcript in the hypothalamus. Levels of GnRH2 mRNA obtained from fish that had been provided excess food for 7 days were higher than those in fish that had been fed normally. These results suggest that, in zebrafish, GnRH2 acts as an anorexigenic factor, as is the case in goldfish.

No MeSH data available.


Related in: MedlinePlus

(A) A photograph showing ICV administered-solution containing 0.05% Evans Blue into the brain. Scale bar is 1 mm. (B) Effect of ICV administration of GnRH2 on food intake in the zebrafish. Each column and bar represents the mean and SEM, respectively, and the numbers in parentheses in the panels indicate the number of fish in each group. Significances of differences at each time point were evaluated by one-way ANOVA with the Bonferroni’s method in comparison with the vehicle-injected group (**P < 0.01).
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Figure 1: (A) A photograph showing ICV administered-solution containing 0.05% Evans Blue into the brain. Scale bar is 1 mm. (B) Effect of ICV administration of GnRH2 on food intake in the zebrafish. Each column and bar represents the mean and SEM, respectively, and the numbers in parentheses in the panels indicate the number of fish in each group. Significances of differences at each time point were evaluated by one-way ANOVA with the Bonferroni’s method in comparison with the vehicle-injected group (**P < 0.01).

Mentions: Details of the methods used for evaluating feeding behavior in zebrafish have been reported elsewhere (Yokobori et al., 2011, 2012). Each fish was normally fed before the experiments began at noon, and placed in a wet sponge under anesthesia with MS-222 (3-aminobenzoic acid ethyl ester; Sigma-Aldrich). A small part of the parietal bone was carefully removed using a surgical blade (No. 19, Futaba, Tokyo, Japan), and then 0.5 μl/g BW of GnRH2 at doses of 0.1 and 1 pmol/g BW was injected into the third ventricle of the brain using a small Hamilton syringe. The gap in the bone was then filled with a surgical agent (Aron Alpha, Sankyo, Japan). The accuracy of the injection site was confirmed after the experiment by examining whether Evans blue dye, injected at the same time, was present in the ventricle (Figure 1A). Control fish in each experiment were injected with the same volume of vehicle (less than 0.01% acetic acid diluted with saline) in the same way as for the experimental group. Each fish that had received an injection was individually placed in a small experimental tank (24 cm in diameter) containing 3.5 l of tap water, and supplied with food equivalent to 3% of its BW. Food intake was measured by directly observing and recording the number of diet pellets eaten by individual fish over 15 and 30 min of commencement of feeding.


Gonadotropin-releasing hormone 2 suppresses food intake in the zebrafish, Danio rerio.

Nishiguchi R, Azuma M, Yokobori E, Uchiyama M, Matsuda K - Front Endocrinol (Lausanne) (2012)

(A) A photograph showing ICV administered-solution containing 0.05% Evans Blue into the brain. Scale bar is 1 mm. (B) Effect of ICV administration of GnRH2 on food intake in the zebrafish. Each column and bar represents the mean and SEM, respectively, and the numbers in parentheses in the panels indicate the number of fish in each group. Significances of differences at each time point were evaluated by one-way ANOVA with the Bonferroni’s method in comparison with the vehicle-injected group (**P < 0.01).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3473230&req=5

Figure 1: (A) A photograph showing ICV administered-solution containing 0.05% Evans Blue into the brain. Scale bar is 1 mm. (B) Effect of ICV administration of GnRH2 on food intake in the zebrafish. Each column and bar represents the mean and SEM, respectively, and the numbers in parentheses in the panels indicate the number of fish in each group. Significances of differences at each time point were evaluated by one-way ANOVA with the Bonferroni’s method in comparison with the vehicle-injected group (**P < 0.01).
Mentions: Details of the methods used for evaluating feeding behavior in zebrafish have been reported elsewhere (Yokobori et al., 2011, 2012). Each fish was normally fed before the experiments began at noon, and placed in a wet sponge under anesthesia with MS-222 (3-aminobenzoic acid ethyl ester; Sigma-Aldrich). A small part of the parietal bone was carefully removed using a surgical blade (No. 19, Futaba, Tokyo, Japan), and then 0.5 μl/g BW of GnRH2 at doses of 0.1 and 1 pmol/g BW was injected into the third ventricle of the brain using a small Hamilton syringe. The gap in the bone was then filled with a surgical agent (Aron Alpha, Sankyo, Japan). The accuracy of the injection site was confirmed after the experiment by examining whether Evans blue dye, injected at the same time, was present in the ventricle (Figure 1A). Control fish in each experiment were injected with the same volume of vehicle (less than 0.01% acetic acid diluted with saline) in the same way as for the experimental group. Each fish that had received an injection was individually placed in a small experimental tank (24 cm in diameter) containing 3.5 l of tap water, and supplied with food equivalent to 3% of its BW. Food intake was measured by directly observing and recording the number of diet pellets eaten by individual fish over 15 and 30 min of commencement of feeding.

Bottom Line: ICV injection of GnRH2 at 0.1 and 1 pmol/g body weight (BW) induced a marked decrease of food consumption in a dose-dependent manner during 30 min after feeding.Levels of GnRH2 mRNA obtained from fish that had been provided excess food for 7 days were higher than those in fish that had been fed normally.These results suggest that, in zebrafish, GnRH2 acts as an anorexigenic factor, as is the case in goldfish.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Regulatory Biology, Graduate School of Science and Engineering, University of Toyama Toyama, Japan.

ABSTRACT
Gonadotropin-releasing hormone (GnRH) is an evolutionarily conserved neuropeptide with 10 amino acid residues, of which several structural variants exist. A molecular form known as GnRH2 ([His(5) Trp(7) Tyr(8)]GnRH, also known as chicken GnRH II) is widely distributed in vertebrates except for rodents, and has recently been implicated in the regulation of feeding behavior in goldfish. However, the influence of GnRH2 on feeding behavior in other fish has not yet been studied. In the present study, therefore, we investigated the role of GnRH2 in the regulation of feeding behavior in a zebrafish model, and examined its involvement in food intake after intracerebroventricular (ICV) administration. ICV injection of GnRH2 at 0.1 and 1 pmol/g body weight (BW) induced a marked decrease of food consumption in a dose-dependent manner during 30 min after feeding. Cumulative food intake was significantly decreased by ICV injection of GnRH2 at 1 pmol/g BW during the 30-min post-treatment observation period. The anorexigenic action of GnRH2 was completely blocked by treatment with the GnRH type I receptor antagonist Antide at 25 pmol/g BW. We also examined the effect of feeding condition on the expression level of the GnRH2 transcript in the hypothalamus. Levels of GnRH2 mRNA obtained from fish that had been provided excess food for 7 days were higher than those in fish that had been fed normally. These results suggest that, in zebrafish, GnRH2 acts as an anorexigenic factor, as is the case in goldfish.

No MeSH data available.


Related in: MedlinePlus