Influence of a 1-h immobilization stress on sleep and CLIP (ACTH(18-39)) brain contents in adrenalectomized rats

Basal sleep amounts in adrenalectomized rats (AdX), as compared to intact a nimals, exhibit a significant increase in slow-wave sleep (SWS), a tendency towards an increase in paradoxical sleep (PS), and circadian rhythms (SWS and PS) flattened in amplitude. An immobilization stress (IS) of 1 h, impos ed on AdX rats at the beginning of the dark period, is accompanied by an in tense polygraphic waking. Just after the IS, SWS amount become significantl y higher than in control rats (+ 44%/11 h of darkness) whereas significant increases of PS occur only 5-10 h after the IS (+ 24%/11 h of darkness). A specific radioimmunoassay for CLIP (corticotropin-like intermediate lobe pe ptide or ACTH(18-39)) was performed in biopsies taken either from the nucle us raphe dorsalis (nRD) or the arcuate nucleus (AN). In the nRD, just after the IS, phosphorylated CLIP (Ph-CLIP) concentration exhibits a decreasing tendency, but 4 h later, it increases significantly (+ 22%, p < 0.05). In t he AN, Ph-CLIP concentration remains unchanged after the IS as well as 4 h later. These results differ from those previously reported in intact animal s also submitted to a 1-h IS, that is, a SWS rebound less marked (+ 27%/11 h of darkness), a PS rebound more important starting immediately after the IS (+ 46%/11 h of darkness) and a significant increase in Ph-CLIP occurring just after the end of the restraint. In conclusion, data obtained after a restraint stress either in AdX or in control rats point out the dependence of the PS rebound on the nRD Ph-CLIP concentration. (C) 2000 Elsevier Scien ce B.V. All rights reserved.