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Intracerebroventricular injection of exendin (5–39) increases food intake of layer-type chicks but not broiler chicks
Brain Research 915 (2001) 234–237 www.elsevier.com / locate / bres
Short communication
Intracerebroventricular injection of exendin (5–39) increases food intake of layer-type chicks but not broiler chicks a b, c c Tetsuya Tachibana , Kunio Sugahara *, Atsushi Ohgushi , Ryuichi Ando , c c c Kouichi Sashihara , Takao Yoshimatsu , Mitsuhiro Furuse b
a United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183 -8509, Japan Laboratory of Nutritional Biochemistry, Department of Animal Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya 321 -8505, Japan c Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and Bioenvironmental Science, Kyushu University, Fukuoka 812 -8581, Japan
Accepted 13 June 2001
Abstract To clarify the involvement of endogenous glucagon-like peptide-1 (GLP-1) on feeding in chicks, we examined the central effect of GLP-1 antagonist, exendin (5–39) on food intake. Intracerebroventricular co-injection of exendin (5–39) with GLP-1 attenuated the anorexigenic effect of GLP-1 in layer-type chicks. Furthermore, exendin (5–39) enhanced food intake of layer-type chicks under ad libitum feeding. However, this effect was not observed in broiler chicks. Therefore, endogenous GLP-1 may be important in the regulation of feeding in layer-type chicks but not in broiler chicks. 2001 Elsevier Science B.V. All rights reserved. Theme: Neural basis of behavior Topic: Ingestive behaviors Keywords: Broiler chick; Exendin (5–39); Feeding; Glucagon-like peptide-1; Layer-type chick
Previous studies have shown that intracerebroventricular(ly) (ICV) injection of glucagon-like peptide-1 (GLP-1) suppresses feeding in rats [12]. When exendin (9–39), a GLP-1 receptor antagonist, was ICV injected in rats, food intake increased [12]. Therefore, it is thought that endogenous GLP-1 may regulate feeding in rats. ICV injection of GLP-1 also strongly inhibits food intake in broiler chicks [4,5]. However, ICV injection of exendin (9–39) did not alter the food intake of broiler chicks [6]. This result suggests that endogenous GLP-1 in the brain is not crucial factor in the regulation of feeding in chicks. There are more potent antagonists of GLP-1 receptor rather than exendin (9–39). One of them, exendin (5–39) provides about 10-fold higher potency as an antagonist than exendin (9–39) [7]. In order to clarify the actual role
*Corresponding author. Tel.: 181-28-649-5441; fax: 181-28-6495443. E-mail address: [email protected] (K. Sugahara).
of GLP-1 on feeding, exendin (5–39) is believed to be better than exendin (9–39). Present study was carried out to elucidate whether endogenous GLP-1 is involved in the regulation of feeding in two different breeds of chicks by applying exendin (5–39). Firstly, we investigated the effect of ICV coinjection of exendin (5–39) with GLP-1 on food intake in layer-type chicks. Secondary, we compared the effect of ICV injection of exendin (5–39) on food intake in both layer-type and broiler-type chicks under an ad libitum feeding condition, since body weight and food intake are largely different between these two strains [9]. Day-old male layer-type chicks (Boris Brown) and broiler chicks (Cobb) were purchased from local hatcheries (Murata Hatchery, Fukuoka, Japan and Mori Hatchery, Fukuoka, Japan, respectively). Birds were maintained in a windowless room at a constant temperature of 288C. Lighting was provided continuously. They were given free access to water and a commercial chick starter diet (Toyohashi Feed and Mills, Aichi, Japan). Birds were maintained in accordance with the recommendations of the
0006-8993 / 01 / $ – see front matter 2001 Elsevier Science B.V. All rights reserved. PII: S0006-8993( 01 )02943-2
T. Tachibana et al. / Brain Research 915 (2001) 234 – 237
National Research Council [8]. The birds were distributed into experimental groups based on their body weight, so that the mean body weight was as uniform as possible for each group. The birds were ICV injected with each drug according to the method of Davis et al. [1] at a volume of 10 ml. Exendin (5–39) and chicken GLP-1 (7–36) amide were purchased from Peptide Institute (Osaka, Japan). Drugs were dissolved in a 0.1% Evans Blue solution which was prepared in 0.85% saline. Food intake was determined by measuring the disappearance diet from pre-weighed feeder. The weight of feeder was measured by using an electric digital balance of precision 61 mg. Experiment 1 was carried out to test the antagonism of exendin (5–39) on the anorexigenic effect of GLP-1 after 3 h fasting. Layer-type chicks (4-day-old) were divided into four groups (10 birds per group). Control group was ICV injected with 0.1% Evans Blue solution, and remaining three groups were ICV injected with GLP-1 (0.03 nmol). The dose of GLP-1 was decided as referred to the previous work [4]. Two of GLP-1-injected groups were simultaneously given exendin (5–39) at doses of 0.3 and 0.6 nmol. Food intake was measured over 3 h after injection at 1-h intervals. Experiment 2 was designed to examine the effect of ICV injection of exendin (5–39) on food intake of layer-type chicks under ad libitum feeding condition. Birds (5-dayold) were divided into three groups (10 birds per group). One group was injected with 0.1% Evans Blue solution as control group, and remaining two groups were injected with exendin (5–39) at 0.3 and 0.6 nmol. Food intake was determined at 1, 2 and 3 h after injection. Experiment 3 was planned to examine whether ICV injection of exendin (5–39) stimulates food intake of broiler chicks (2-day-old). This age of broiler chicks have similar body weight with 5-day-old layer-type chicks. The experimental schedule was same as experiment 2. At the end of experiment, the birds were sacrificed by overdose injection of sodium pentobarbital and removed the brains. Verification of drug injection was made by observation of the presence of Evans Blue dye in the lateral ventricle. Data from the individuals that were not verified by the presence of Evans Blue dye in the lateral ventricle were deleted. The data were analyzed by one-way analysis of variance by the General Liner Model procedure using a commercially available package [10]. Comparisons between means were made using Duncan’s multiple range rest. The results are presented as means6S.E.M. Fig. 1 shows the effect of ICV injection of exendin (5–39) on the anorexigenic effect of GLP-1 for 3 h after injection. Food intake was significantly suppressed by GLP-1 at all time investigated. Both levels of exendin (5–39) did not affect the anorexigenic effect of GLP-1 until 2 h after injection (data not shown). At 3 h after
235
Fig. 1. Effect of ICV injection of exendin (5–39) (0.3 or 0.6 nmol) with GLP-1 (0.03 nmol) on food intake in layer-type chicks. Food intake was determined at 3 h after injection. Data are expressed as means6S.E.M. Numbers in the parentheses represent the number of chicks used in each group. Groups with different letters are statistically different (P,0.05).
injection, low level of exendin (5–39) slightly but significantly attenuated the anorexigenic effect of GLP-1. Although high level of exendin (5–39) similarly attenuated the reduction of food intake as well as low level of exendin (5–39), a significant effect was not detected comparing with GLP-1 group. Fig. 2 represents the effect of exendin (5–39) on the food intake of layer-type chicks. Both levels of exendin (5–39) significantly increased food intake at all times determined. Fig. 3 represents the effect of exendin (5–39) on the
Fig. 2. Effect of ICV injection of exendin (5–39) (0.3 or 0.6 nmol) on cumulative food intake of layer-type chicks under ad libitum feeding condition. Data are expressed as means6S.E.M. Numbers in the parentheses represent the number of chicks used in each group. Groups with different letters are statistically different (P,0.05).
236
T. Tachibana et al. / Brain Research 915 (2001) 234 – 237
Fig. 3. Effect of ICV injection of exendin (5–39) (0.3 or 0.6 nmol) on cumulative food intake of broiler chicks under ad libitum feeding condition. Data are expressed as means6S.E.M. Numbers in the parentheses represent the number of chicks used in each group.
food intake of broiler chicks. As shown in Fig. 3, exendin (5–39) did not affect the food intake of broiler chicks over 3 h. It is well known that exendin (5–39) is a potent antagonist of GLP-1 receptor in mammals [7]. We reported here that exendin (5–39) partly attenuated the anorexigenic effect of GLP-1 in layer-type chicks. This suggests that exendin (5–39) can be played as an antagonist of GLP-1 in chicks as well as mammals. However, we did not examine the antagonistic effect of exendine (5–39) on the anorexigenic effect of GLP-1 in broiler chicks. Earlier and present study demonstrate that small amounts (0.03 nmol) of GLP-1 inhibited food intake in both layer-type (present study) and broiler chicks [4], suggesting that the property of GLP-1 receptors of layer-type and broiler chicks are similar. Further works will clarify the antagonistic effect of exendin (5–39) in broiler chicks. Previous studies indicated that the dose of GLP-1 to suppress feeding in broiler chicks [4,5] may be much lower than that in rats [12], being less than 9 pmol in chicks. This fact indicated that GLP-1 receptor were fully expressed in the chick brain. In the present study, however, we have applied high level of GLP-1 (0.03 nmol) which showed a strong effect [4]. In addition, the doses of exendin (5–39) used in the present study were lower than that in mammalian study [12]. Additional experiment using several combinations of GLP-1 and exendin (5–39) will clearly demonstrate the antagonistic effect of exendin (5– 39) in chicks. ICV injection of 0.3 and 0.6 nmol exendin (5–39) increased food intake of layer-type chicks, demonstrating
that endogenous GLP-1 inhibits feeding of layer-type chicks in a normal feeding condition. Interestingly, these doses of exendin (5–39) could not fully attenuate the anorexigenic effect of 0.03 nmol GLP-1 in experiment 1. These suggest that there are small amounts of GLP-1 in the brain of layer-type chicks, enough to be antagonized by 0.3 and 0.6 nmol exendin (5–39). Thus, endogenous GLP-1 may suppress food intake at a low dose in layer-type chicks. On the other hand, these doses of exendin (5–39) did not affect the food intake of broiler chicks. Previous study also demonstrated that exendin (9–39), an another antagonist, did not alter the food intake of broiler chicks [6]. In addition, property of the GLP-1 receptor of broiler chicks seems to be similar to that of layer-type chicks as mentioned above. Since exendin (5–39) stimulated food intake in layer-type chicks, ineffectiveness of both exendins on food intake in broiler chicks may be due to the low anorexigenic effect of endogenous GLP-1 but not the low potency as an antagonist. Thus, present results suggest that the extent of the anorexigenic effect of endogenous GLP-1 is different among the breed of chicks. It is well known that broiler chicks eat more food than layer-type chicks and grow faster [9]. In fact, mean body weight of 2-day-old broiler chicks (68.960.9 g) used in experiment 3 is higher than that of 5-day-old layer-type chicks (62.060.4 g) used in experiment 2. Broiler chickens were genetically selected for a large body weight and fast growing. Furthermore, selection for large body weight is positively associated with the food intake and efficiency of food utilization [11]. Earlier studies demonstrated that ICV injection of 5-hydroxytryptamine, an anorexigenic factor in chicks, inhibits food intake in layer-type chicks [3] but not broiler chicks [2] under fasting condition. It is possible that the differences in food intake and body weight between layer-type and broiler chickens may result from the difference in sensitivity to the anorexigenic factors. Therefore, we hypothesized that the anorexigenic effect of endogenous GLP-1 may be too low to decrease food intake in broiler chicks at least in the neonatal stage, and then the chicks grow faster than layer-type chicks. Further works will be needed to clarify the involvement of endogenous GLP-1 on feeding in neonatal chicks. In conclusion, endogenous GLP-1 would play an important role in the regulation of feeding in layer-type chicks but not in broiler chicks at least in the neonatal stage.
Acknowledgements This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, and Culture of Japan and Uehara Memorial Foundation.
T. Tachibana et al. / Brain Research 915 (2001) 234 – 237
References [1] J.L. Davis, D.T. Masuoka, L.K. Gerbrandt, A. Cherkin, Autoradiographic distribution of L-proline in chicks after intracerebral injection, Physiol. Behav. 22 (1979) 693–695. [2] D.M. Denbow, H.P. Van Krey, J.A. Cherry, Feeding and drinking response of young chicks to injection of serotonin into the lateral ventricle of the brain, Poult. Sci. 61 (1982) 150–155. [3] D.M. Denbow, H.P. Van Krey, M.P. Lacy, T.J. Dietrick, Feeding, drinking and body temperature of Leghorn chicks: effects of ICV injections of biogenic amines, Physiol. Behav. 31 (1983) 85–90. [4] M. Furuse, M. Matsumoto, R. Mori, K. Sugahara, S. Hasegawa, 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 Res. 764 (1997) 289–292. [5] 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. 755 (1997) 167–169. [6] M. Furuse, T. Bungo, M. Shimojo, Y. Masuda, N. Saito, S. Hasegawa, K. Sugahara, Influence of intracerebroventricular ad-
[7]
[8]
[9] [10] [11] [12]
237
ministration of exendin (9-39) on food intake of the newly-hatched chick, Jpn. Poult. Sci. 35 (1998) 376–380. C. Montrose-Rafizadeh, H. Yang, B.D. Rodgers, A. Beday, L.A. Pritchette, J. Eng, High potency antagonists of the pancreatic glucagon-like peptide-1 receptor, J. Biol. Chem. 272 (1997) 21201– 21206. National Research Council, Guide for the Care and Use of Laboratory Animals. NIH Publ. No. 85-23, Department of Health and Human Services, Washington, DC, USA, 1985. National Research Council, Nutrient Requirements of Poultry, Ninth Revised Edition, The National Academy of Sciences, USA, 1994. SAS Institute, SAS User’s Guide: Statistics, 5th Edition, SAS Institute, Cary, NC, 1985. P.B. Siegel, E.L. Wisman, Changes in appetite and feed utilization, Poult. Sci. 45 (1966) 1391–1397. M.D. Turton, D. O’Shea, I. Gunn, S.A. Beak, C.M. Edwards, K. Meeran, S.J. Choi, G.M. Taylor, M.M. Heath, P.D. Lambert, J.P. 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 (1996) 69–72.
Short communication
Intracerebroventricular injection of exendin (5–39) increases food intake of layer-type chicks but not broiler chicks a b, c c Tetsuya Tachibana , Kunio Sugahara *, Atsushi Ohgushi , Ryuichi Ando , c c c Kouichi Sashihara , Takao Yoshimatsu , Mitsuhiro Furuse b
a United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183 -8509, Japan Laboratory of Nutritional Biochemistry, Department of Animal Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya 321 -8505, Japan c Laboratory of Advanced Animal and Marine Bioresources, Graduate School of Bioresource and Bioenvironmental Science, Kyushu University, Fukuoka 812 -8581, Japan
Accepted 13 June 2001
Abstract To clarify the involvement of endogenous glucagon-like peptide-1 (GLP-1) on feeding in chicks, we examined the central effect of GLP-1 antagonist, exendin (5–39) on food intake. Intracerebroventricular co-injection of exendin (5–39) with GLP-1 attenuated the anorexigenic effect of GLP-1 in layer-type chicks. Furthermore, exendin (5–39) enhanced food intake of layer-type chicks under ad libitum feeding. However, this effect was not observed in broiler chicks. Therefore, endogenous GLP-1 may be important in the regulation of feeding in layer-type chicks but not in broiler chicks. 2001 Elsevier Science B.V. All rights reserved. Theme: Neural basis of behavior Topic: Ingestive behaviors Keywords: Broiler chick; Exendin (5–39); Feeding; Glucagon-like peptide-1; Layer-type chick
Previous studies have shown that intracerebroventricular(ly) (ICV) injection of glucagon-like peptide-1 (GLP-1) suppresses feeding in rats [12]. When exendin (9–39), a GLP-1 receptor antagonist, was ICV injected in rats, food intake increased [12]. Therefore, it is thought that endogenous GLP-1 may regulate feeding in rats. ICV injection of GLP-1 also strongly inhibits food intake in broiler chicks [4,5]. However, ICV injection of exendin (9–39) did not alter the food intake of broiler chicks [6]. This result suggests that endogenous GLP-1 in the brain is not crucial factor in the regulation of feeding in chicks. There are more potent antagonists of GLP-1 receptor rather than exendin (9–39). One of them, exendin (5–39) provides about 10-fold higher potency as an antagonist than exendin (9–39) [7]. In order to clarify the actual role
*Corresponding author. Tel.: 181-28-649-5441; fax: 181-28-6495443. E-mail address: [email protected] (K. Sugahara).
of GLP-1 on feeding, exendin (5–39) is believed to be better than exendin (9–39). Present study was carried out to elucidate whether endogenous GLP-1 is involved in the regulation of feeding in two different breeds of chicks by applying exendin (5–39). Firstly, we investigated the effect of ICV coinjection of exendin (5–39) with GLP-1 on food intake in layer-type chicks. Secondary, we compared the effect of ICV injection of exendin (5–39) on food intake in both layer-type and broiler-type chicks under an ad libitum feeding condition, since body weight and food intake are largely different between these two strains [9]. Day-old male layer-type chicks (Boris Brown) and broiler chicks (Cobb) were purchased from local hatcheries (Murata Hatchery, Fukuoka, Japan and Mori Hatchery, Fukuoka, Japan, respectively). Birds were maintained in a windowless room at a constant temperature of 288C. Lighting was provided continuously. They were given free access to water and a commercial chick starter diet (Toyohashi Feed and Mills, Aichi, Japan). Birds were maintained in accordance with the recommendations of the
0006-8993 / 01 / $ – see front matter 2001 Elsevier Science B.V. All rights reserved. PII: S0006-8993( 01 )02943-2
T. Tachibana et al. / Brain Research 915 (2001) 234 – 237
National Research Council [8]. The birds were distributed into experimental groups based on their body weight, so that the mean body weight was as uniform as possible for each group. The birds were ICV injected with each drug according to the method of Davis et al. [1] at a volume of 10 ml. Exendin (5–39) and chicken GLP-1 (7–36) amide were purchased from Peptide Institute (Osaka, Japan). Drugs were dissolved in a 0.1% Evans Blue solution which was prepared in 0.85% saline. Food intake was determined by measuring the disappearance diet from pre-weighed feeder. The weight of feeder was measured by using an electric digital balance of precision 61 mg. Experiment 1 was carried out to test the antagonism of exendin (5–39) on the anorexigenic effect of GLP-1 after 3 h fasting. Layer-type chicks (4-day-old) were divided into four groups (10 birds per group). Control group was ICV injected with 0.1% Evans Blue solution, and remaining three groups were ICV injected with GLP-1 (0.03 nmol). The dose of GLP-1 was decided as referred to the previous work [4]. Two of GLP-1-injected groups were simultaneously given exendin (5–39) at doses of 0.3 and 0.6 nmol. Food intake was measured over 3 h after injection at 1-h intervals. Experiment 2 was designed to examine the effect of ICV injection of exendin (5–39) on food intake of layer-type chicks under ad libitum feeding condition. Birds (5-dayold) were divided into three groups (10 birds per group). One group was injected with 0.1% Evans Blue solution as control group, and remaining two groups were injected with exendin (5–39) at 0.3 and 0.6 nmol. Food intake was determined at 1, 2 and 3 h after injection. Experiment 3 was planned to examine whether ICV injection of exendin (5–39) stimulates food intake of broiler chicks (2-day-old). This age of broiler chicks have similar body weight with 5-day-old layer-type chicks. The experimental schedule was same as experiment 2. At the end of experiment, the birds were sacrificed by overdose injection of sodium pentobarbital and removed the brains. Verification of drug injection was made by observation of the presence of Evans Blue dye in the lateral ventricle. Data from the individuals that were not verified by the presence of Evans Blue dye in the lateral ventricle were deleted. The data were analyzed by one-way analysis of variance by the General Liner Model procedure using a commercially available package [10]. Comparisons between means were made using Duncan’s multiple range rest. The results are presented as means6S.E.M. Fig. 1 shows the effect of ICV injection of exendin (5–39) on the anorexigenic effect of GLP-1 for 3 h after injection. Food intake was significantly suppressed by GLP-1 at all time investigated. Both levels of exendin (5–39) did not affect the anorexigenic effect of GLP-1 until 2 h after injection (data not shown). At 3 h after
235
Fig. 1. Effect of ICV injection of exendin (5–39) (0.3 or 0.6 nmol) with GLP-1 (0.03 nmol) on food intake in layer-type chicks. Food intake was determined at 3 h after injection. Data are expressed as means6S.E.M. Numbers in the parentheses represent the number of chicks used in each group. Groups with different letters are statistically different (P,0.05).
injection, low level of exendin (5–39) slightly but significantly attenuated the anorexigenic effect of GLP-1. Although high level of exendin (5–39) similarly attenuated the reduction of food intake as well as low level of exendin (5–39), a significant effect was not detected comparing with GLP-1 group. Fig. 2 represents the effect of exendin (5–39) on the food intake of layer-type chicks. Both levels of exendin (5–39) significantly increased food intake at all times determined. Fig. 3 represents the effect of exendin (5–39) on the
Fig. 2. Effect of ICV injection of exendin (5–39) (0.3 or 0.6 nmol) on cumulative food intake of layer-type chicks under ad libitum feeding condition. Data are expressed as means6S.E.M. Numbers in the parentheses represent the number of chicks used in each group. Groups with different letters are statistically different (P,0.05).
236
T. Tachibana et al. / Brain Research 915 (2001) 234 – 237
Fig. 3. Effect of ICV injection of exendin (5–39) (0.3 or 0.6 nmol) on cumulative food intake of broiler chicks under ad libitum feeding condition. Data are expressed as means6S.E.M. Numbers in the parentheses represent the number of chicks used in each group.
food intake of broiler chicks. As shown in Fig. 3, exendin (5–39) did not affect the food intake of broiler chicks over 3 h. It is well known that exendin (5–39) is a potent antagonist of GLP-1 receptor in mammals [7]. We reported here that exendin (5–39) partly attenuated the anorexigenic effect of GLP-1 in layer-type chicks. This suggests that exendin (5–39) can be played as an antagonist of GLP-1 in chicks as well as mammals. However, we did not examine the antagonistic effect of exendine (5–39) on the anorexigenic effect of GLP-1 in broiler chicks. Earlier and present study demonstrate that small amounts (0.03 nmol) of GLP-1 inhibited food intake in both layer-type (present study) and broiler chicks [4], suggesting that the property of GLP-1 receptors of layer-type and broiler chicks are similar. Further works will clarify the antagonistic effect of exendin (5–39) in broiler chicks. Previous studies indicated that the dose of GLP-1 to suppress feeding in broiler chicks [4,5] may be much lower than that in rats [12], being less than 9 pmol in chicks. This fact indicated that GLP-1 receptor were fully expressed in the chick brain. In the present study, however, we have applied high level of GLP-1 (0.03 nmol) which showed a strong effect [4]. In addition, the doses of exendin (5–39) used in the present study were lower than that in mammalian study [12]. Additional experiment using several combinations of GLP-1 and exendin (5–39) will clearly demonstrate the antagonistic effect of exendin (5– 39) in chicks. ICV injection of 0.3 and 0.6 nmol exendin (5–39) increased food intake of layer-type chicks, demonstrating
that endogenous GLP-1 inhibits feeding of layer-type chicks in a normal feeding condition. Interestingly, these doses of exendin (5–39) could not fully attenuate the anorexigenic effect of 0.03 nmol GLP-1 in experiment 1. These suggest that there are small amounts of GLP-1 in the brain of layer-type chicks, enough to be antagonized by 0.3 and 0.6 nmol exendin (5–39). Thus, endogenous GLP-1 may suppress food intake at a low dose in layer-type chicks. On the other hand, these doses of exendin (5–39) did not affect the food intake of broiler chicks. Previous study also demonstrated that exendin (9–39), an another antagonist, did not alter the food intake of broiler chicks [6]. In addition, property of the GLP-1 receptor of broiler chicks seems to be similar to that of layer-type chicks as mentioned above. Since exendin (5–39) stimulated food intake in layer-type chicks, ineffectiveness of both exendins on food intake in broiler chicks may be due to the low anorexigenic effect of endogenous GLP-1 but not the low potency as an antagonist. Thus, present results suggest that the extent of the anorexigenic effect of endogenous GLP-1 is different among the breed of chicks. It is well known that broiler chicks eat more food than layer-type chicks and grow faster [9]. In fact, mean body weight of 2-day-old broiler chicks (68.960.9 g) used in experiment 3 is higher than that of 5-day-old layer-type chicks (62.060.4 g) used in experiment 2. Broiler chickens were genetically selected for a large body weight and fast growing. Furthermore, selection for large body weight is positively associated with the food intake and efficiency of food utilization [11]. Earlier studies demonstrated that ICV injection of 5-hydroxytryptamine, an anorexigenic factor in chicks, inhibits food intake in layer-type chicks [3] but not broiler chicks [2] under fasting condition. It is possible that the differences in food intake and body weight between layer-type and broiler chickens may result from the difference in sensitivity to the anorexigenic factors. Therefore, we hypothesized that the anorexigenic effect of endogenous GLP-1 may be too low to decrease food intake in broiler chicks at least in the neonatal stage, and then the chicks grow faster than layer-type chicks. Further works will be needed to clarify the involvement of endogenous GLP-1 on feeding in neonatal chicks. In conclusion, endogenous GLP-1 would play an important role in the regulation of feeding in layer-type chicks but not in broiler chicks at least in the neonatal stage.
Acknowledgements This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, and Culture of Japan and Uehara Memorial Foundation.
T. Tachibana et al. / Brain Research 915 (2001) 234 – 237
References [1] J.L. Davis, D.T. Masuoka, L.K. Gerbrandt, A. Cherkin, Autoradiographic distribution of L-proline in chicks after intracerebral injection, Physiol. Behav. 22 (1979) 693–695. [2] D.M. Denbow, H.P. Van Krey, J.A. Cherry, Feeding and drinking response of young chicks to injection of serotonin into the lateral ventricle of the brain, Poult. Sci. 61 (1982) 150–155. [3] D.M. Denbow, H.P. Van Krey, M.P. Lacy, T.J. Dietrick, Feeding, drinking and body temperature of Leghorn chicks: effects of ICV injections of biogenic amines, Physiol. Behav. 31 (1983) 85–90. [4] M. Furuse, M. Matsumoto, R. Mori, K. Sugahara, S. Hasegawa, 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 Res. 764 (1997) 289–292. [5] 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. 755 (1997) 167–169. [6] M. Furuse, T. Bungo, M. Shimojo, Y. Masuda, N. Saito, S. Hasegawa, K. Sugahara, Influence of intracerebroventricular ad-
[7]
[8]
[9] [10] [11] [12]
237
ministration of exendin (9-39) on food intake of the newly-hatched chick, Jpn. Poult. Sci. 35 (1998) 376–380. C. Montrose-Rafizadeh, H. Yang, B.D. Rodgers, A. Beday, L.A. Pritchette, J. Eng, High potency antagonists of the pancreatic glucagon-like peptide-1 receptor, J. Biol. Chem. 272 (1997) 21201– 21206. National Research Council, Guide for the Care and Use of Laboratory Animals. NIH Publ. No. 85-23, Department of Health and Human Services, Washington, DC, USA, 1985. National Research Council, Nutrient Requirements of Poultry, Ninth Revised Edition, The National Academy of Sciences, USA, 1994. SAS Institute, SAS User’s Guide: Statistics, 5th Edition, SAS Institute, Cary, NC, 1985. P.B. Siegel, E.L. Wisman, Changes in appetite and feed utilization, Poult. Sci. 45 (1966) 1391–1397. M.D. Turton, D. O’Shea, I. Gunn, S.A. Beak, C.M. Edwards, K. Meeran, S.J. Choi, G.M. Taylor, M.M. Heath, P.D. Lambert, J.P. 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 (1996) 69–72.