Interleukin-1 receptor immunoreactivity in sympathetic vascular and non-vascular neurons in guinea-pig coeliac ganglion

Abstract Immunoreactivity (IR) for the interleukin-1 receptor type I (IL1RI) was examined in sympathetic neurons in guinea-pig coeliac ganglion using multiple-labelling immunofluorescence. IL1RI-IR was present in 8% of sympathetic neurons in untreated preparations. The proportion of neurons with IL1RI-IR increased significantly after incubation in interleukin-6 (200 ng/ml) for 2–4 h (16–26% neurons), or after incubation for 4 h without cytokine (16%), with interleukin-1β (IL1β, 200 ng/ml; 18%) or tumour necrosis factor-α (200 ng/ml; 16%). This increase occurred predominantly in neuropeptide Y-IR, vasoconstrictor neurons. IL1RI-IR also was present in varicose axons, some of which projected from the gut, and in vascular smooth muscle cells and endothelium. These potential binding sites for the proinflammatory cytokine, IL1β, on vasoconstrictor neurons and blood vessels may modulate sympathetic regulation of intestinal blood flow in inflammatory conditions.