BRAIN DISTRIBUTION OF VASOACTIVE-INTESTINAL-PEPTIDE RECEPTORS FOLLOWING REM-SLEEP DEPRIVATION

Vasoactive intestinal peptide (VIP) has been shown to increase rapid e ye movement (REM) sleep in normal and insomniac animals, while the adm inistration of anti-VIP antibodies or an antagonist of VIP receptors d ecreases REM sleep. In addition, recently, it has been suggested that a VIP-like substance accumulates in the CSF during waking and that it may be involved in the production of the REM rebound normally seen fol lowing REM sleep deprivation. This evidence suggests that VIP may be i mportant in modulating REM sleep in normal conditions and during REM s leep rebound. To determine whether VIP is involved in REM sleep homeos tasis, VIP receptors of discrete brain areas was determined by autorad iography after 24 and 72 h of REM sleep deprivation (REM SD) by the wa ter tank technique. Since this procedure has been suggested to produce some stress, an additional group adapted for 7 days to the sleep depr ivation situation was tested. The results showed that REM SD produces an increase in the density of VIP receptors in several brainstem and f orebrain structures at 24 h of REM SD and more so at 72 h of REM SD. I nterestingly, results showed that habituation to the REM SD procedure decreases the density of VIP receptors in some areas of the brain of t he REM sleep-deprived rats. The results are discussed in terms of the possibility that waking induces an increase of VIP receptors in severa l structures, which in turn are responsible for modulating REM sleep, but that stress contributes in part to VIP receptor changes.