Central histaminergic system interplay with suppressive effects of immune challenge on food intake in chicken

Biomolecules Triggering Altered Food Intake during Pathogenic Challenge in Chicks

Food intake is regulated by several complicated synergistic mechanisms that are affected by a variety of internal and external influences. Some of these factors include those that are released from pathogens such as bacteria, fungi, and viruses, and most of these factors are associated with suppression of the chick's food intake. Although chicks are well-known to decrease their food intake when they experience a pathogenic challenge, the mechanisms that mediate this type of satiety are poorly understood. One of the goals of our research group has been to better understand these mechanisms in chicks. We recently provided evidence that pathogen-associated molecular patterns, which are recognized by pattern-recognition receptors such as Toll-like receptors, likely contribute to satiety in chicks that are experiencing a pathogenic challenge. Additionally, we identified several inflammatory cytokines, including interleukin-1β, tumor necrosis factor-like cytokine 1A, prostaglandins, and nitric oxide, that likely contribute to satiety during a pathogenic challenge. This review summarizes the current knowledge on pathogen-induced satiety in chicks mainly accumulated through our recent research. The research will give good information to improve the loss of production during infection in poultry production in the future.

Endogenous Nitric Oxide and Dopamine Regulate Feeding Behavior in Neonatal Layer-type Chickens

Evidence from animal studies suggests that endogenous nitric oxide and dopamine (DA) have a regulatory role in the rewarding system, but their interaction(s) have not been studied in avian species. In this study, 4 experiments were performed to determine the effects of central administration of L-arginine (nitric oxide precursor; 200 nmol), NG-nitro-L-arginine methyl ester (L-NAME, a nitric oxide synthase inhibitor; 100 nmol), amphetamine (an indirect DA agonist; 125 pmol) and DA (40 pmol) on feeding behavior in neonatal layer-type chickens (each experiment included 4 groups, n=12 birds in each group). Prior to the initiation of the treatments, birds were fasted for 3 hours (FD3). In experiment 1, chickens received intracerebroventricular (ICV) injection of saline, L-NAME (100 nmol), amphetamine (125 pmol), and combination of L-NAME + amphetamine. In experiment 2, chickens received the ICV injection of saline, L-arginine (200 nmol), amphetamine (125 pmol) and their combination. In experiment 3, chickens received ICV injection of saline, L-arginine (200 nmol), DA (40 pmol) and L-arginine + DA. In experiment 4, chickens received ICV injection of saline, L-NAME (100 nmol), DA (40 pmol) and L-NAME + DA. Thereafter, the cumulative food intake (on the basis of metabolic body weight) was recorded until 2-h post injection. The results showed that ICV injection of amphetamine or DA significantly decreased food intake (P<0.05). Also, co-administration of L-NAME + amphetamine attenuated the hypophagic effect of amphetamine (P<0.05), while combined administration of L-NAME and DA had no effect on DA-induced hypophagia. Additionally, the hypophagic effect of amphetamine was significantly amplified by L-arginine (P<0.05), but the combination of L-arginine and DA did not alter feeding behavior which was induced by DA. These results suggest an interaction between DAergic and nitrergic systems via a presynaptic mechanism on food intake regulation in layer-type chicken.