Submitted to: World's Poultry Science Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 21, 2005
Publication Date: N/A
Interpretive Summary: The sympathetic nervous system plays important roles in regulating a variety of cellular activities in the body to maintain physiological homeostasis, including modulation of immune responses to internal and external stimuli. The discovery of highly specific adrenoceptor agonists and antagonists has opened a new channel for investigating the role of the sympathetic nervous system in regulating physiological homeostasis including immunity. The present study showed that clonidine induced differential immune reactions, i.e., an increase in some parameters of the humoral-immunity without effects on the cell-immunity in chickens. The unique effects of clonidine on the different immune systems may indicate that different types and or subtypes of adrenoceptors were involved in these reactions. The characteristic of clonidine-induced immune response in chickens could prove beneficial in chicken management, such as administering clonidine early after birds are relocated from the grower house to layer house and during induced molting. These practices are traditionally used in the egg industry and cause birds to be stressed, which increases their susceptibility to infection.
Technical Abstract: The ability of the sympathetic nervous system to regulate chicken immune functions was examined. Clonidine, an alpha-2 adrenergic receptor agonist, was administrated at 2.5, 5.0 or 10.0 mg/L in the drinking water of White Leghorn hens at 48 wks of age. The hens were randomly housed in conventional cages in pairs. Concentrations of plasma IgG (also named IgY) were detected using chicken IgG ELISA, and the percentage of subsets of circulating immunocompetent cells were analyzed using flow cytometry. Compared to controls, treated hens had higher circulating IgG levels and a greater percentage of circulating B-cells (Bu-1+ cells, P < 0.01) after 1 week of treatment. In the treated hens, there was also a consistent tendency for an increase of the percentages of CD 8+ cells but not for CD 4+ cells which remained unaffected (P = 0.07, P > 0.05, respectively). These effects of clonidine on the IgG concentrations and the proportions of B-, and CD8+-cells were dose related. The highest increase was found in the hens treated with 10.0 mg/L. These results suggest that the sympathetic nervous system is directly involved in regulating chickens’ immunity via regulation of alpha 2-adrenoceptor activations.