ABSTRACT
It is now known that after an immobilization stress (IS) of short duration (1h), adult rats exhibit a significant rapid eye movement (REM) sleep rebound. In this study, we examined this phenomenon in aged animals. We found that aged rats subjected to an IS did not show a sleep rebound after the restraint, in contrast to younger animals. Plasma corticosterone and corticotrophin (ACTH(1)(-)(39)) levels were, however, similar in aged and adult rats. The corticotrophin-like intermediate lobe peptide (CLIP or ACTH(18)(-)(39)) system of the arcuate nucleus, suggested to be involved in REM sleep genesis by way of pontine projections (HP: the hypothalamo-pontine axis), was also not different between aged and young rats. The lack of REM sleep rebound observed in aged animals is thus independent of the HPA (hypothalamo-pituitary-adrenal) and HP axe activities. The causal impairments might reside in REM sleep executive structures of the dorsal pontine tegmentum.
