- Email: [email protected]
Influence of fasting and neuropeptide Y on the suppressive food intake induced by intracerebroventricular injection of glucagon-like peptide-1 in the neonatal chick
Brain Research 764 Ž1997. 289–292
Short communication
Influence of fasting and neuropeptide Y on the suppressive food intake induced by intracerebroventricular injection of glucagon-like peptide-1 in the neonatal chick Mitsuhiro Furuse
a, )
, Megumi Matsumoto a , Ryoichi Mori a , Kunio Sugahara b , Koichiro Kano c , Shin Hasegawa c
a
c
Laboratory of Animal Nutrition, School of Agricultural Sciences, Nagoya UniÕersity, Nagoya 464-01, Japan b Department of Animal Science, Faculty of Agriculture, Utsunomiya UniÕersity, Utsunomiya 321, Japan Laboratory of Biological Function and Metabolism, DiÕision of Bioscience, Graduate School of Science and Technology, Kobe UniÕersity, Kobe-shi 657, Japan Accepted 6 May 1997
Abstract Recently, we have reported that central administration of glucagon-like peptide-1 ŽGLP-1. strongly decreased food intake of chicks. The aim of the present study was to elucidate whether suppressed food intake by central injection of GLP-1 would be modified by an appetite stimulant such as fasting and neuropeptide Y ŽNPY.. Birds Ž2 days old. were starved for 3 or 6 h and then GLP-1 Ž0.03 m gr10 m l. or saline was injected by the intracerebroventricular Ži.c.v.. route. Birds starved for 6 h ate significantly more food than those starved for 3 h, while irrespective of the time for fasting GLP-1 strongly inhibited food intake as rapidly as 10 min after i.c.v injection. The suppressive effect on food intake continued until 4 h after injection. Central administration of NPY Ž2.5 m gr10 m l. greatly enhanced food intake, but co-injection of GLP-1 Ž0.01, 0.02 or 0.03 m gr10 m l. decreased food intake in a dose-dependent fashion. Under GLP-1 Ž0.03 m gr10 m l. treatment, whether NPY modifies food intake of chicks in a dose-dependent manner was investigated by co-injection of graded levels of NPY Ž0.4, 1.0 and 2.5 m gr10 m l.. GLP-1 completely inhibited the effect of NPY on food intake without a dose response. These results suggest that central GLP-1 may interact with NPY and may be the most potent inhibitor of food intake in the chicken. q 1997 Elsevier Science B.V. Keywords: Glucagon-like peptide-1 ŽGLP-1.; Neuropeptide Y ŽNPY.; Central; Feeding behavior; Chicken
In mammalian species, proglucagon is shown to contain two glucagon-like sequences, flanked by pairs of basic amino acids, known as the potential cleavage site. These two peptides are named glucagon-like peptide ŽGLP.-1 and GLP-2. The amino acid sequences of mammalian GLP-1 are identical with those of the bovine w10x, porcupine w11x, hamster w1x, guinea pig w15x, rat w7x, human w4x and pig w12x. In chickens, however, some differences in amino acid sequence are observed, being different at four positions w6x. Furthermore, chicken proglucagon does not contain GLP-2
) Corresponding author. Present address: Laboratory of Animal Feed Science, Faculty of Agriculture, Kyushu University, Fukuoka 812-81, Japan. Fax: q81 Ž92. 642-2953; E-mail: [email protected]
0006-8993r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved. PII S 0 0 0 6 - 8 9 9 3 Ž 9 7 . 0 0 6 2 3 - 9
and this fact suggests that GLP-2 has no essential role in mammals w6x. Recently, GLP-1 has been shown to be related to feeding behavior; central administration of GLP-1 strongly inhibited food intake of rats w17,18x. We reported that central injection of mammalian and chicken GLP-1 similarly inhibited food intake in the chick w5x. Moreover, only a small amount of GLP-1 Ž0.03 m g. was required to suppress food intake, implying that GLP-1 is an intrinsic factor to control food intake in the chick. According to Turton et al. w18x, c-fos appeared exclusively in the paraventricular nucleus ŽPVN. of the hypothalamus and central nucleus of the amygdala following intracerebroventricular Ži.c.v.. GLP-1 injection. Endogenous neuropeptide Y ŽNPY., a potent stimulator of food intake, releases in the PVN w8x. However, the effect of
290
M. Furuse et al.r Brain Research 764 (1997) 289–292
NPY on food intake was decreased by GLP-1 in the rat w18x. GLP-1 and NPY may interact in the PVN. The present study was to elucidate whether suppressed food intake by the central injection of GLP-1 would be modified by appetite stimulants such as fasting and NPY. Day-old broiler chicks of both sexes were purchased from a local hatchery ŽFusoen, Aichi, Japan.. The birds were maintained in a room with 24 h light and at a temperature of 288C. They were given free access to a commercial starter diet ŽNihon Nosan Kogyo Co. Ltd., Tokyo, Japan.. The birds were distributed into experimental groups based on their body weight, so that average body weight was as uniform as possible within the same experiment. Immediately before receiving the diet, birds were fixed in a device w3x and i.c.v. injected with the solutions Ž10 m l. using a microsyringe. Chicken GLP-1Ž7–36. and porcine NPY were purchased from Peptide Institute, Inc. ŽOsaka, Japan.. GLP-1 was dissolved in a 0.1% Evans Blue solution, which was prepared in 0.85% saline. After 3 or 6 h fasting, in experiment 1, birds Ž2 days old, 7 birds per group. were given the diet for 4 h after i.c.v. administration of GLP-1 Ž0.03 m g. or saline. Food intake was measured at 10, 20, 30, 60, 120, 180 and 240 min. In experiment 2, birds Ž2 days old, 8 birds per group fed ad libitum. were injected by i.c.v. route with saline, NPY Ž2.5 m g. or NPY co-injected with graded levels of GLP-1 Ž0.01, 0.02 or 0.03 m g.. In the third experiment, birds were divided into 5 groups Ž8 birds each fed ad libitum., i.e., GLP-1 Ž0.03 m g. co-injected with four levels of NPY Ž0, 0.4, 1 and 2.5 m g. and NPY Ž2.5 m g. alone. Food intake was determined at 30, 60 and 120 min in experiments 2 and 3. At the end of the experiments, the birds were killed by decapitation, followed by brain sectioning to identify location of drug injection. Data from the individuals that were not verified by the presence of Evans Blue dye in the lateral ventricle were discarded. Data were subjected to two-way Žexperiment 1. and one-way Žexperiments 2 and 3. analysis of variance ŽANOVA. by the General Linear Model procedure using a commercially available package w14x, and comparisons between means were made using Duncan’s multiple range test. The results are indicated as the mean " S.E.M. Fig. 1 shows cumulative food intake of birds injected i.c.v. with GLP-1 or saline after 3 or 6 h fasting in experiment 1. Food intake was inhibited as rapidly as 10 min after injection of GLP-1 and this suppressed effect on food intake continued until the end of the experiment. Birds starved for 6 h ate significantly more food compared with those fasting for 3 h. No significant interactions were observed between fasting time and GLP at any of the time points studied, implying that the effect of GLP-1 on food intake was independent of fasting times used here. So far, it has been confirmed that endogenous NPY
Fig. 1. Cumulative food intake of chicks administered i.c.v. with chicken glucagon-like peptide-1 ŽGLP-1; 0.03 m g. or saline after 3 or 6 h fasting. At all the times measured, food intake was significantly higher in the birds starved for 6 h than in those for 3 h and GLP-1 significantly inhibited food intake. No significant interactions between fasting time and GLP-1 were detected at any time point.
releases in the PVN w8x and hypothalamic prepro-NPY messenger RNA levels w2,13,19x are increased with fasting and normalized by refeeding. In the rat, the specific GLP-1 binding sites in the brain were detected in the hypothalamus, especially PVN, the central nucleus of the amygdala and the anterodorsal thalamic nucleus w18x. According to Turton et al. w18x, i.c.v. administration of GLP-1 Ž10 m g. immediately before NPY Ž10 m g. injection greatly reduced food intake in the rat. Thus, we have confirmed the interaction between GLP-1 and NPY in the food intake of the chick by the following two experiments. Kuenzel et al. w9x reported that i.c.v. NPY Ž5 and 9 m g,
Fig. 2. Cumulative food intake of chicks injected i.c.v. with saline, NPY Ž2.5 m g. or NPY co-injected with graded levels of GLP-1 Ž0.01, 0.02 or 0.03 m g. under ad libitum feeding. Means with a different letter are significantly different at p- 0.05.
M. Furuse et al.r Brain Research 764 (1997) 289–292
291
Acknowledgements This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan.
References
Fig. 3. Cumulative food intake of chicks injected i.c.v. with NPY Ž2.5 m g. alone or GLP-1 Ž0.03 m g. with four levels of NPY Ž0, 0.4, 1 and 2.5 m g. under ad libitum feeding. ) Significantly different from other groups at p- 0.05.
but not 1 m g. strongly increased food intake in broiler chicks Žmore than 2 weeks of age., while Steinman et al. w16x observed that NPY did not elevate consumption significantly in a dose-related fashion in neonatal Leghorn chicks Ž2 days old.. In our preliminary experiment using 3-day-old broiler chicks, the effect of central NPY at the levels of 1, 2.5 and 5 m g was identical and all the levels of NPY stimulated food intake of the neonatal chicks compared with the saline control. The response for NPY in feeding behavior may be altered by age and strains of birds. As shown in Fig. 2 Žexperiment 2., 2.5 m g of NPY strongly stimulated food intake when compared with the control. However, the stimulated food intake by NPY was depressed, in a dose-dependent fashion, with co-injection of a small amount of GLP-1. We have speculated in the previous report that levels of less than 0.03 m g GLP-1 might be effective for the inhibition of food intake in the chick w5x. This may be true, because 0.01 m g GLP-1 significantly suppressed the food intake enhanced by NPY. In experiment 3, the graded levels of NPY were administered with a constant level of GLP-1 Ž0.03 m g. to investigate whether NPY enhances food intake of chicks in a dose-response manner under the suppression by GLP-1. GLP-1 strongly inhibited the effect of NPY irrespective of its levels ŽFig. 3.. In turn, under the circumstances in which NPY release is stimulated, the stimulant effect of food intake by NPY may be completely nullified if a small amount of GLP-1 is simultaneously released. On the other hand, no change in NPY mRNA was found following i.c.v. GLP-1 injection w18x. The relationship between GLP-1 mRNA and NPY mRNA remains to be studied. The results presented here suggest that central GLP-1 may interact with NPY and may be the most potent inhibitor of food intake in the chicken.
w1x G.I. Bell, R.F. Santerre, G.T. Mullenbach, Hamster preproglucagon contains the sequence of glucagon and two related peptides, Nature 302 Ž1983. 716–718. w2x L.S. Brady, M.A. Smith, P.W. Gold, M. Herkenham, Altered expression of hypothalamic neuropeptide mRNAs in food-restricted and food-deprived rats, Neuroendocrinology 52 Ž1990. 441–447. w3x J.L. Davis, D.T. Masuoka, L.K. Gerbrandt, A. Cherkin, Autoradiographic distribution of L-proline in chicks after intracerebral injection, Physiol. Behav. 22 Ž1979. 693–695. w4x D.J. Drucker, S. Asa, Glucagon gene expression in vertebrate brain, J. Biol. Chem. 263 Ž1988. 13475–13478. w5x M. Furuse, M. Matsumoto, J. Okumura, K. Sugahara, S. Hasegawa, Intracerebroventricular injection of mammalian and chicken glucagon-like peptide-1 inhibits food intake of the neonatal chick, Brain Res. Ž1997. in press. w6x S. Hasegawa, K. Terazono, K. Nata, T. Takada, H. Yamamoto, H. Okamoto, Nucleotide sequence determination of chicken glucagon precursor cDNA. Chicken preproglucagon does not contain glucagon-like peptide II, FEBS Lett. 264 Ž1990. 117–120. w7x G. Heinrich, P. Gros, P.K. Lund, R.C. Bentley, J.F. Habener, Pre-proglucagon messenger ribonucleic acid: nucleotide and encoded amino acid sequences of the rat pancreatic complementary deoxyribonucleic acid, Endocrinology 115 Ž1984. 2176–2181. w8x S.P. Kalra, M.G. Dube, A. Sahu, C.P. Phelps, P.S. Kalra, Neuropeptide Y secretion increases in the paraventricular nucleus in association with increased appetite for food, Proc. Natl. Acad. Sci. USA 88 Ž1991. 10931–10935. w9x W.J. Kuenzel, L.W. Douglass, B.A. Davison, Robust feeding following central administration of neuropeptide Y or peptide YY in chicks, Gallus domesticus, Peptides 8 Ž1987. 823–828. w10x L.C. Lopez, M.L. Frazier, C.J. Su, A. Kumar, G.F. Saunders, Mammalian pancreatic preproglucagon contains three glucagon-related peptides, Proc. Natl. Acad. Sci. USA 80 Ž1983. 5485–5489. w11x M. Nishi, D.F. Steiner, Cloning of complementary DNAs encoding islet amyloid polypeptide, insulin, and glucagon precursors from a New World rodent, the degu, Octodon degus, Mol. Endocrinol. 4 Ž1990. 1192–1198. w12x C. Ørskov, M. Bersani, A.H. Johnsen, P. Hojrup, J.J. Holst, Complete sequences of glucagon-like peptide-1 from human and pig small intestine, J. Biol. Chem. 264 Ž1989. 12826–12829. w13x R.D. O’Shea, A.L. Gundlach, Preproneuropeptide Y messenger ribonucleic acid in the hypothalamic arcuate nucleus of the rat is increased by food deprivation or dehydration, J. Neuroendocrinol. 3 Ž1991. 11–14. w14x SAS Institute, Inc., SAS User’s Guide: Statistics, 5th ed., SAS Institute, Cary, NC, 1985. w15x S. Seino, M. Welsh, G.I. Bell, S.J. Chan, D.F. Steiner, Mutations in the guinea pig preproglucagon gene are restricted to a specific portion of the prohormone sequence, FEBS Lett. 203 Ž1986. 25–30. w16x J.L. Steinman, D.G. Fujikawa, C.G. Wasterlain, A. Cherkin, J.E. Morley, The effects of adrenergic, opioid and pancreatic polypeptidergic compounds on feeding and other behaviors in neonatal Leghorn chicks, Peptides 8 Ž1987. 585–592. w17x M. Tang-Christensen, P.J. Larsen, R. Goke, ¨ A. Fink-Jensen, D.S. Jessop, M. Møller, S.P. Sheikh, Central administration of GLP-1-
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Ž7–36. amide inhibits food and water intake in rats, Am. J. Physiol. 271 Ž1996. R848–R856. w18x M.D. Turton, D. O’Shea, I. Gunn, S.A. Beak, C.M.B. Edwards, K. Meeran, S.J. Choi, G.M. Tayler, M.M. Heath, P.D. Lambert, J.P.H. Wilding, D.M. Smith, M.A. Ghatei, J. Herbert, S.R. Bloom, A role
for glucagon-like peptide-1 in the central regulation of feeding, Nature 379 Ž1996. 69–72. w19x J.D. White, M. Kershaw, Increased hypothalamic neuropeptide Y expression following food deprivation, Mol. Cell Neurosci. 1 Ž1990. 41–48.
Short communication
Influence of fasting and neuropeptide Y on the suppressive food intake induced by intracerebroventricular injection of glucagon-like peptide-1 in the neonatal chick Mitsuhiro Furuse
a, )
, Megumi Matsumoto a , Ryoichi Mori a , Kunio Sugahara b , Koichiro Kano c , Shin Hasegawa c
a
c
Laboratory of Animal Nutrition, School of Agricultural Sciences, Nagoya UniÕersity, Nagoya 464-01, Japan b Department of Animal Science, Faculty of Agriculture, Utsunomiya UniÕersity, Utsunomiya 321, Japan Laboratory of Biological Function and Metabolism, DiÕision of Bioscience, Graduate School of Science and Technology, Kobe UniÕersity, Kobe-shi 657, Japan Accepted 6 May 1997
Abstract Recently, we have reported that central administration of glucagon-like peptide-1 ŽGLP-1. strongly decreased food intake of chicks. The aim of the present study was to elucidate whether suppressed food intake by central injection of GLP-1 would be modified by an appetite stimulant such as fasting and neuropeptide Y ŽNPY.. Birds Ž2 days old. were starved for 3 or 6 h and then GLP-1 Ž0.03 m gr10 m l. or saline was injected by the intracerebroventricular Ži.c.v.. route. Birds starved for 6 h ate significantly more food than those starved for 3 h, while irrespective of the time for fasting GLP-1 strongly inhibited food intake as rapidly as 10 min after i.c.v injection. The suppressive effect on food intake continued until 4 h after injection. Central administration of NPY Ž2.5 m gr10 m l. greatly enhanced food intake, but co-injection of GLP-1 Ž0.01, 0.02 or 0.03 m gr10 m l. decreased food intake in a dose-dependent fashion. Under GLP-1 Ž0.03 m gr10 m l. treatment, whether NPY modifies food intake of chicks in a dose-dependent manner was investigated by co-injection of graded levels of NPY Ž0.4, 1.0 and 2.5 m gr10 m l.. GLP-1 completely inhibited the effect of NPY on food intake without a dose response. These results suggest that central GLP-1 may interact with NPY and may be the most potent inhibitor of food intake in the chicken. q 1997 Elsevier Science B.V. Keywords: Glucagon-like peptide-1 ŽGLP-1.; Neuropeptide Y ŽNPY.; Central; Feeding behavior; Chicken
In mammalian species, proglucagon is shown to contain two glucagon-like sequences, flanked by pairs of basic amino acids, known as the potential cleavage site. These two peptides are named glucagon-like peptide ŽGLP.-1 and GLP-2. The amino acid sequences of mammalian GLP-1 are identical with those of the bovine w10x, porcupine w11x, hamster w1x, guinea pig w15x, rat w7x, human w4x and pig w12x. In chickens, however, some differences in amino acid sequence are observed, being different at four positions w6x. Furthermore, chicken proglucagon does not contain GLP-2
) Corresponding author. Present address: Laboratory of Animal Feed Science, Faculty of Agriculture, Kyushu University, Fukuoka 812-81, Japan. Fax: q81 Ž92. 642-2953; E-mail: [email protected]
0006-8993r97r$17.00 q 1997 Elsevier Science B.V. All rights reserved. PII S 0 0 0 6 - 8 9 9 3 Ž 9 7 . 0 0 6 2 3 - 9
and this fact suggests that GLP-2 has no essential role in mammals w6x. Recently, GLP-1 has been shown to be related to feeding behavior; central administration of GLP-1 strongly inhibited food intake of rats w17,18x. We reported that central injection of mammalian and chicken GLP-1 similarly inhibited food intake in the chick w5x. Moreover, only a small amount of GLP-1 Ž0.03 m g. was required to suppress food intake, implying that GLP-1 is an intrinsic factor to control food intake in the chick. According to Turton et al. w18x, c-fos appeared exclusively in the paraventricular nucleus ŽPVN. of the hypothalamus and central nucleus of the amygdala following intracerebroventricular Ži.c.v.. GLP-1 injection. Endogenous neuropeptide Y ŽNPY., a potent stimulator of food intake, releases in the PVN w8x. However, the effect of
290
M. Furuse et al.r Brain Research 764 (1997) 289–292
NPY on food intake was decreased by GLP-1 in the rat w18x. GLP-1 and NPY may interact in the PVN. The present study was to elucidate whether suppressed food intake by the central injection of GLP-1 would be modified by appetite stimulants such as fasting and NPY. Day-old broiler chicks of both sexes were purchased from a local hatchery ŽFusoen, Aichi, Japan.. The birds were maintained in a room with 24 h light and at a temperature of 288C. They were given free access to a commercial starter diet ŽNihon Nosan Kogyo Co. Ltd., Tokyo, Japan.. The birds were distributed into experimental groups based on their body weight, so that average body weight was as uniform as possible within the same experiment. Immediately before receiving the diet, birds were fixed in a device w3x and i.c.v. injected with the solutions Ž10 m l. using a microsyringe. Chicken GLP-1Ž7–36. and porcine NPY were purchased from Peptide Institute, Inc. ŽOsaka, Japan.. GLP-1 was dissolved in a 0.1% Evans Blue solution, which was prepared in 0.85% saline. After 3 or 6 h fasting, in experiment 1, birds Ž2 days old, 7 birds per group. were given the diet for 4 h after i.c.v. administration of GLP-1 Ž0.03 m g. or saline. Food intake was measured at 10, 20, 30, 60, 120, 180 and 240 min. In experiment 2, birds Ž2 days old, 8 birds per group fed ad libitum. were injected by i.c.v. route with saline, NPY Ž2.5 m g. or NPY co-injected with graded levels of GLP-1 Ž0.01, 0.02 or 0.03 m g.. In the third experiment, birds were divided into 5 groups Ž8 birds each fed ad libitum., i.e., GLP-1 Ž0.03 m g. co-injected with four levels of NPY Ž0, 0.4, 1 and 2.5 m g. and NPY Ž2.5 m g. alone. Food intake was determined at 30, 60 and 120 min in experiments 2 and 3. At the end of the experiments, the birds were killed by decapitation, followed by brain sectioning to identify location of drug injection. Data from the individuals that were not verified by the presence of Evans Blue dye in the lateral ventricle were discarded. Data were subjected to two-way Žexperiment 1. and one-way Žexperiments 2 and 3. analysis of variance ŽANOVA. by the General Linear Model procedure using a commercially available package w14x, and comparisons between means were made using Duncan’s multiple range test. The results are indicated as the mean " S.E.M. Fig. 1 shows cumulative food intake of birds injected i.c.v. with GLP-1 or saline after 3 or 6 h fasting in experiment 1. Food intake was inhibited as rapidly as 10 min after injection of GLP-1 and this suppressed effect on food intake continued until the end of the experiment. Birds starved for 6 h ate significantly more food compared with those fasting for 3 h. No significant interactions were observed between fasting time and GLP at any of the time points studied, implying that the effect of GLP-1 on food intake was independent of fasting times used here. So far, it has been confirmed that endogenous NPY
Fig. 1. Cumulative food intake of chicks administered i.c.v. with chicken glucagon-like peptide-1 ŽGLP-1; 0.03 m g. or saline after 3 or 6 h fasting. At all the times measured, food intake was significantly higher in the birds starved for 6 h than in those for 3 h and GLP-1 significantly inhibited food intake. No significant interactions between fasting time and GLP-1 were detected at any time point.
releases in the PVN w8x and hypothalamic prepro-NPY messenger RNA levels w2,13,19x are increased with fasting and normalized by refeeding. In the rat, the specific GLP-1 binding sites in the brain were detected in the hypothalamus, especially PVN, the central nucleus of the amygdala and the anterodorsal thalamic nucleus w18x. According to Turton et al. w18x, i.c.v. administration of GLP-1 Ž10 m g. immediately before NPY Ž10 m g. injection greatly reduced food intake in the rat. Thus, we have confirmed the interaction between GLP-1 and NPY in the food intake of the chick by the following two experiments. Kuenzel et al. w9x reported that i.c.v. NPY Ž5 and 9 m g,
Fig. 2. Cumulative food intake of chicks injected i.c.v. with saline, NPY Ž2.5 m g. or NPY co-injected with graded levels of GLP-1 Ž0.01, 0.02 or 0.03 m g. under ad libitum feeding. Means with a different letter are significantly different at p- 0.05.
M. Furuse et al.r Brain Research 764 (1997) 289–292
291
Acknowledgements This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan.
References
Fig. 3. Cumulative food intake of chicks injected i.c.v. with NPY Ž2.5 m g. alone or GLP-1 Ž0.03 m g. with four levels of NPY Ž0, 0.4, 1 and 2.5 m g. under ad libitum feeding. ) Significantly different from other groups at p- 0.05.
but not 1 m g. strongly increased food intake in broiler chicks Žmore than 2 weeks of age., while Steinman et al. w16x observed that NPY did not elevate consumption significantly in a dose-related fashion in neonatal Leghorn chicks Ž2 days old.. In our preliminary experiment using 3-day-old broiler chicks, the effect of central NPY at the levels of 1, 2.5 and 5 m g was identical and all the levels of NPY stimulated food intake of the neonatal chicks compared with the saline control. The response for NPY in feeding behavior may be altered by age and strains of birds. As shown in Fig. 2 Žexperiment 2., 2.5 m g of NPY strongly stimulated food intake when compared with the control. However, the stimulated food intake by NPY was depressed, in a dose-dependent fashion, with co-injection of a small amount of GLP-1. We have speculated in the previous report that levels of less than 0.03 m g GLP-1 might be effective for the inhibition of food intake in the chick w5x. This may be true, because 0.01 m g GLP-1 significantly suppressed the food intake enhanced by NPY. In experiment 3, the graded levels of NPY were administered with a constant level of GLP-1 Ž0.03 m g. to investigate whether NPY enhances food intake of chicks in a dose-response manner under the suppression by GLP-1. GLP-1 strongly inhibited the effect of NPY irrespective of its levels ŽFig. 3.. In turn, under the circumstances in which NPY release is stimulated, the stimulant effect of food intake by NPY may be completely nullified if a small amount of GLP-1 is simultaneously released. On the other hand, no change in NPY mRNA was found following i.c.v. GLP-1 injection w18x. The relationship between GLP-1 mRNA and NPY mRNA remains to be studied. The results presented here suggest that central GLP-1 may interact with NPY and may be the most potent inhibitor of food intake in the chicken.
w1x G.I. Bell, R.F. Santerre, G.T. Mullenbach, Hamster preproglucagon contains the sequence of glucagon and two related peptides, Nature 302 Ž1983. 716–718. w2x L.S. Brady, M.A. Smith, P.W. Gold, M. Herkenham, Altered expression of hypothalamic neuropeptide mRNAs in food-restricted and food-deprived rats, Neuroendocrinology 52 Ž1990. 441–447. w3x J.L. Davis, D.T. Masuoka, L.K. Gerbrandt, A. Cherkin, Autoradiographic distribution of L-proline in chicks after intracerebral injection, Physiol. Behav. 22 Ž1979. 693–695. w4x D.J. Drucker, S. Asa, Glucagon gene expression in vertebrate brain, J. Biol. Chem. 263 Ž1988. 13475–13478. w5x M. Furuse, M. Matsumoto, J. Okumura, K. Sugahara, S. Hasegawa, Intracerebroventricular injection of mammalian and chicken glucagon-like peptide-1 inhibits food intake of the neonatal chick, Brain Res. Ž1997. in press. w6x S. Hasegawa, K. Terazono, K. Nata, T. Takada, H. Yamamoto, H. Okamoto, Nucleotide sequence determination of chicken glucagon precursor cDNA. Chicken preproglucagon does not contain glucagon-like peptide II, FEBS Lett. 264 Ž1990. 117–120. w7x G. Heinrich, P. Gros, P.K. Lund, R.C. Bentley, J.F. Habener, Pre-proglucagon messenger ribonucleic acid: nucleotide and encoded amino acid sequences of the rat pancreatic complementary deoxyribonucleic acid, Endocrinology 115 Ž1984. 2176–2181. w8x S.P. Kalra, M.G. Dube, A. Sahu, C.P. Phelps, P.S. Kalra, Neuropeptide Y secretion increases in the paraventricular nucleus in association with increased appetite for food, Proc. Natl. Acad. Sci. USA 88 Ž1991. 10931–10935. w9x W.J. Kuenzel, L.W. Douglass, B.A. Davison, Robust feeding following central administration of neuropeptide Y or peptide YY in chicks, Gallus domesticus, Peptides 8 Ž1987. 823–828. w10x L.C. Lopez, M.L. Frazier, C.J. Su, A. Kumar, G.F. Saunders, Mammalian pancreatic preproglucagon contains three glucagon-related peptides, Proc. Natl. Acad. Sci. USA 80 Ž1983. 5485–5489. w11x M. Nishi, D.F. Steiner, Cloning of complementary DNAs encoding islet amyloid polypeptide, insulin, and glucagon precursors from a New World rodent, the degu, Octodon degus, Mol. Endocrinol. 4 Ž1990. 1192–1198. w12x C. Ørskov, M. Bersani, A.H. Johnsen, P. Hojrup, J.J. Holst, Complete sequences of glucagon-like peptide-1 from human and pig small intestine, J. Biol. Chem. 264 Ž1989. 12826–12829. w13x R.D. O’Shea, A.L. Gundlach, Preproneuropeptide Y messenger ribonucleic acid in the hypothalamic arcuate nucleus of the rat is increased by food deprivation or dehydration, J. Neuroendocrinol. 3 Ž1991. 11–14. w14x SAS Institute, Inc., SAS User’s Guide: Statistics, 5th ed., SAS Institute, Cary, NC, 1985. w15x S. Seino, M. Welsh, G.I. Bell, S.J. Chan, D.F. Steiner, Mutations in the guinea pig preproglucagon gene are restricted to a specific portion of the prohormone sequence, FEBS Lett. 203 Ž1986. 25–30. w16x J.L. Steinman, D.G. Fujikawa, C.G. Wasterlain, A. Cherkin, J.E. Morley, The effects of adrenergic, opioid and pancreatic polypeptidergic compounds on feeding and other behaviors in neonatal Leghorn chicks, Peptides 8 Ž1987. 585–592. w17x M. Tang-Christensen, P.J. Larsen, R. Goke, ¨ A. Fink-Jensen, D.S. Jessop, M. Møller, S.P. Sheikh, Central administration of GLP-1-
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M. Furuse et al.r Brain Research 764 (1997) 289–292
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