Distribution of interleukin-1 receptor in chicken and quail brain

Interleukin 1 isoforms (IL-1) are major regulators of vertebrate immune responses. In the mammalian CNS, this function is reflected in physiological and anatomical evidence implicating IL-1 in a suite of behaviors associated with sickness. Although birds show sickness behavior, a parallel role of IL-1 in birds has not been investigated. As proinflammatory effects of IL-1 are mediated via the IL-1 type I receptor (IL-1RI), we investigated the distribution of IL-1RI protein and mRNA after lipopolysaccharide challenge in brains of two avian species, the chicken and Japanese quail. In some respects, the neuroanatomic distribution of IL-1R mRNA and protein in chicken and Japanese quail resembled that reported in mammals and was consistent with its putative role in the physiology and behavior of sickness. For example, we found IL-1RI mRNA or IL-1RI immunoreactivity in lemnothalamic visual projection areas of the pallium, surrounding blood vessels in pallial areas, in the dorsomedial nucleus of the hypothalamus, in the nucleus taenia, in cerebeller Purkinje cells and the motor components of the trigeminal and vagus nuclei. However, in contrast to mammals, we did not find evidence of IL1-RI receptors in medial or lateral pallial structures, paraventricular nucleus, areas homologous to the arcuate nucleus, the choroid plexus, organum vasculosum of the lamina terminalis or the reticular activating system. The distribution of IL-1RI suggests that a role for IL-1 in sickness behavior is conserved in birds, but that roles in other putative mammalian functions (e.g. hypothalamic-pituitary-adrenal and gonadal axes regulation, transport through barrier-related tissues, arousal) may differ.