Roles of central interleukin-1 on stress-induced-hypertension and footshock-induced-analgesia in rats.

Central interleukin-1 (IL-1) plays an important role in mediating the neural, endocrine, and behavioral responses to stressors. Here we tested whether central IL-1 is involved in stress-induced hypertension or footshock (FS)-induced-analgesia. We observed that: (1) intracerebral ventricular injection of (ICV) IL-1beta induced pressor responses; (2) hypertension induced by IL-1beta was blocked by ICV an IL-1 antagonist, IL-1ra; (3) ICV IL-1ra attenuated the pressor response induced by FS but intravenous injection of IL-1ra did not significantly reduce this response; (4) the hypertensive response to conditioned fear stimuli was reversed by ICV IL-1ra; (5) FS-induced-analgesia was attenuated by ICV IL-1ra and this effect disappeared 15 min after ICV IL-1ra. These results suggest that both the pressor response to FS or conditioned fear stimuli and short lasting analgesia induced by FS are mediated by central IL-1.