SLEEP PERMISSIVE COMPONENTS WITHIN THE DORSAL RAPHE NUCLEUS IN THE RAT

Two peptides known for their hypnogenic properties, CLIP (corticotropi n-like intermediate lobe peptide or ACTH 18-39) or VIP (vasoactive int estinal polypeptide), were injected locally into the nucleus raphe dor salis (nRD) of rats pretreated with p-chlorophenylalanine (PCPA). Duri ng the dark period, the PCPA insomnia was primarily associated with a reduction in paradoxical sleep (PS), whereas both slow wave sleep (SWS ) and PS were decreased during the light period. Immunohistochemistry of serotonin in PCPA-pretreated animals indicated a clear disappearanc e of 5-HT fibers in the basal hypothalamus and the nRD as compared to control animals. Local injections of CLIP or VIP in the nRD restored P S and SWS. The positive injection sites corresponded to the anatomical distribution of either CLIP or VIP fibers, i.e., the entire nRD for V IP and the antero-dorsal part of this nucleus for CLIP. The sleep effe cts obtained in PCPA-pretreated rats involve a non-5-HT sleep permissi ve component within the nRD upon which these injected peptides act.