Effects of Interleukin-1  on Blood Pressure, Sympathetic Nerve Activity, and Pituitary Endocrine Functions in Anesthetized Rats

The effects of interleukin-1 beta (IL-1), an endogenous pyrogen, on both the central and peripheral endocrine, sympathetic, and cardiovascular systems were investigated by injecting it intracisternally (IC) and intravenously (IV). Intracisternal injections of IL-1 caused dose-dependent vasopressor responses, which were accompanied by corresponding increases in the abdominal sympathetic discharge. Blood pressure increased gradually, and attained a peak response at 20 to 30 min. Heart rate also increased dose-dependently. Intracerebroventricular pretreatments with indomethacin abolished both the pressor responses and tachycardia. The IV injections similarly elicited vasopressor responses with gradual onset, which were also accompanied by corresponding increases in the abdominal sympathetic firings. However, IL-1 did not constrict the peripheral vasculature in the perfused hindlimb preparation. Both IC and IV injections of IL-1 increased plasma vasopressin and corticotropin dose-dependently after 30 min. These results indicate that IL-1 of both central and peripheral origin may cause vasopressor responses. These may be partly mediated by the release of vasopressor pituitary hormones. The site of action could be a similar region in the central nervous system.