Interactions of Cholecystokinin and Glutamatergic Systems in Feeding Behavior of Neonatal Chickens

Abstract

This study aimed to assess the possible feeding behavior alterations by central interactions of cholecystokinin (CCK) and glutamatergic systems in neonatal chickens. In experiment 1, chickens received intracerebroventricular (ICV) administration of saline and CCK (CCK₄; 0.25, 0.5, and 1 nmol). In experiment 2, birds were ICV injected with saline, CCK_8s (0.25, 0.5, and 1 nmol). In experiment 3, chickens received the ICV injection of saline, CCK_8s (1 nmol), MK-801 (15 nmol), and co-injection of the CCk_8s+MK-801. Experiments 4-7 were performed similar to experiment 3, except for chickens that were injected with CNQX (390 nmol), AIDA (2 nmol), LY341495 (150 nmol), and UBP1112 (2 nmol) instead of MK-801. Subsequently, the total amount of the consumed food was determined. According to the results, the ICV administration of CCK₄ (0.25, 0.5, and 1 nmol) could not affect the food intake in chickens (P>0.05). The ICV injection of the CCK_8s (0.25, 0.5, and 1 nmol) led to a dose-dependent hypophagia (P<0.05). Moreover, hypophagia induced by CCK_8s decreased by the co-injection of the CCK_8s+MK-801 (P<0.05). These results showed that the hypophagic effects of the CCK on food intake can be mediated by NMDA glutamate receptors in layer-type chickens.

Keywords: Chickens; Cholecystokinin; Food intake; Glutamatergic.

Figure 1

Effect of the ICV injection of CCK₄ (0.25, 0.5, and 1 nmol) on the cumulative food intake in neonatal layer chicken (n=44). CCK₄: Cholecystokinin fragment 30-33 amide. Data are expressed as mean±SEM.

Figure 2

Effect of the ICV injection of CCK_8s (0.25, 0.5, and 1 nmol) on cumulative food intake in neonatal layer chicken (n=44). CCK_8s: Cholecystokinin fragment 26-33 amide, sulfated. Data are expressed as mean±SEM. Different letters (a, b, c, and d) indicate significant differences among treatments (P<0.05).

Figure 3

Effects of the ICV injection of control solution, CCk_8s (Cholecystokinin fragment 26-33 amide, sulfated; 1 nmol), MK-801 (NMDA glutamate receptors antagonist; 15 nmol), and co-injection of the CCk_8s+MK-801 on cumulative food intake (g/100g BW) in neonatal layer chicken. Data are expressed as mean±SEM. Different letters (a and b) indicate significant differences among treatments at each time (P<0.05).

Figure 4

Effects of the ICV injection of control solution, CCk_8s (Cholecystokinin fragment 26-33 amide, sulfated; 1 nmol), CNQX (AMPA glutamate receptors antagonist; 390 nmol), and co-injection of the CCk_8s+CNQX on cumulative food intake (g/100g BW) in neonatal layer chicken. Data are expressed as mean±SEM. Different letters (a and b) indicate significant differences among treatments at each time (P<0.05).

Figure 5

Effects of the ICV injection of control solution, CCk_8s (Cholecystokinin fragment 26-33 amide, sulfated; 1 nmol), AIDA (mGLUR₁ glutamate receptors antagonist; 2 nmol), and co-injection of the CCk_8s+AIDA on cumulative food intake (g/100g BW) in neonatal layer chicken. Data are expressed as mean±SEM. Different letters (a and b) indicate significant differences among treatments at each time (P<0.05).

Figure 6

Effects of the ICV injection of control solution, CCk_8s (Cholecystokinin fragment 26-33 amide, sulfated; 1 nmol), LY341495 (mGLUR₂ glutamate receptors antagonist; 150 nmol), and co-injection of the CCk_8s+LY341495 on cumulative food intake (g/100g BW) in neonatal layer chicken. Data are expressed as mean±SEM. Different letters (a and b) indicate significant differences among treatments at each time (P<0.05).

Figure 7

Effects of the ICV injection of control solution, CCk_8s (Cholecystokinin fragment 26-33 amide, sulfated; 1 nmol), UBP1112 (mGLUR₃ glutamate receptors antagonist; 2 nmol), and co-injection of the CCk_8s+UBP1112 on cumulative food intake (g/100g BW) in neonatal layer chicken. Data are expressed as mean±SEM. Different letters (a and b) indicate significant differences among treatments at each time (P<0.05).