Cardiorespiratory responses to interleukin-1β in adult rats: Role of nitric oxide, eicosanoids and glucocorticoids

Interleukin-1β (IL-1β) receptors are abundantly expressed in brain stem regions involved in respiratory control. We hypothesized that systemic administration of IL-1β would increase ventilation (V̇(E)), and that nitric oxide, eicosanoids, and glucocorticoid receptors would modulate IL-1β- induced cardioventilatory responses. Intravenous injections of three doses (37.5 ng kg^-1, 75 ng kg^-1 and 150 ng kg^-1) of IL-1β induced monophasic increases in (V̇(E)), heart rate (HR), and blood pressure (BP) which had a distinctly different onset and duration of action compared to IL-1β-induced body temperature elevations. Pre-treatment with the nitric oxide inhibitor L- NAME was associated with decreased peak V̇E responses, without affecting the latency and duration of IL-1β. L-NAME also enhanced HR responses while pressor responses were attenuated. Eicosanoid inhibition with indomethacin resulted in markedly attenuated V̇ responses. However, cardiovascular responses to IL-1β were not modified by indomethacin. In contrast, pre- treatment with dexamethasone, was not associated with any changes in the IL- 1β-induced V̇(E), HR, or BP responses. We conclude that IL- 1β increases of V̇(E) are dose-dependent and are not time-locked with the pyrexic response suggesting the possibility that distinct neural pathways may underlie these responses. In addition, nitric oxide and eicosanoid-dependent mechanisms modulate IL-1β ventilatory effects.