Interleukin-1beta and calcitonin, but not corticotropin-releasing factor, alter sleep cycles when injected into the rat hypothalamic lateral paraventricular area.

Interleukin-1beta (II-1beta) is a cytokine known to have somnogenic properties. We have previously shown that II-1beta decreases food intake when injected into the lateral part of the paraventricular nucleus of the hypothalamus (PVH), and, because food intake and sleep are closely related behaviors, we tested the hypothesis that II-1beta could alter sleep when injected into the lateral PVH area. We compared the effects of II-1beta with those of two other peptides involved in feeding behavior and known to act in the PVH area, the corticotropin-releasing factor (CRF) and salmon calcitonin (sCT). The EEG of rats was recorded for 48 h after the injection. The results showed that CRF had no effects, II-1beta reduced significantly sleep duration during the first 5 h following the injection, and sCT profoundly affected sleep cycles, producing an almost 30-h long insomnia, with a major reduction of slow wave sleep and a long period of alternation of REM sleep and wakening. It is concluded that (i) the area between the lateral part of the PVH and the fornix is a brain site involved in sleep regulation, (ii) II-1beta, a peptide generally considered as somnogenic, decreases sleep when administered in this area, and (iii) sCT is an extremely potent suppressor of slow wave sleep.