Molecular Cloning of Forebrain mRNAs which are Modulated by Sleep Deprivation

Sleep deprivation (SD) experiments have suggested that specific endogenous substances mediate the control of sleep and waking. However, such 'sleep substances' have not yet been unambiguously identified. The isolation of specific molecular markers would make it possible to obtain new insights into the regulatory mechanism underlying sleep and waking. For this purpose, we have used a molecular genetical approach based on subtractive cDNA cloning. Using these techniques, we were able to detect and isolate in rat forebrain four cDNA clones whose corresponding transcripts are expressed at a lower level after 24 h of SD, and six cDNA clones whose corresponding transcripts are expressed at a higher level. For two of the former transcripts, the level showed a significant reduction of approximately 50% after 24 h of SD and a non-significant reduction after 12 h of SD. A significant reduction was also observed after 12 h of cold exposure. A regional analysis of their level under baseline conditions revealed variation during the 24-h cycle. The highest levels tended to occur at the onset of darkness, the beginning of the rat's activity period. Our results are compatible with the hypothesis that the cloned transcripts are associated with the regulation of the sleep-waking cycle. Analysis of their primary structure indicated that these mRNAs have not yet been characterized. The in vivo distribution of these transcripts in the forebrain shows some correspondence to that of receptors of excitatory amino acids, suggesting an association between the functional role of the cloned sequences and this neurotransmission system.