Noradrenaline release in hypothalamus and ACTH secretion induced by central interleukin-1β

The effect of interleukin-l β (IL-1 β, 10 ng per 5 /A i.e.v.) on noradrenaline release in the hypothalamus of freely moving rats and on plasma ACTH levels has been studied, respectively by intracerebral microdialysis and radioimmunoassay. IL-1/3 induced an early increase in noradrenaline (NA) release in the paraventricular nucleus (PVN) followed by a second long-lasting enhancement starting from 80 min, with a maximum at 140 min (187 ± 14%). Heat-denatured IL-1/3 induced only the early increase without any other change at later times. IL-1/3 did not significantly affect NA release in the area surrounding the PVN at any time. IL-1/3 increased ACTH levels at 2 and 3 h. Indomethacin (10 mg kg", i.p.) prevented the noradrenergic and ACTH responses. The NA system in the PVN plays a part in the mechanism controlling the ACTH response induced by IL-1.