Sleep deprivation increases rat hypothalamic growth hormone-releasing hormone mRNA

Much evidence indicates that growth hormone-releasing hormone (GHRH) is inv olved in sleep regulation. We hypothesized that GHRH mRNA would increase an d somatostatin (SRIH) mRNA would decrease during sleep deprivation. With th e use of RT-PCR and truncated internal standards, rat hypothalamic GHRH mRN A and SRIH mRNA levels were evaluated after sleep deprivation. After 8 or 1 2 h of sleep deprivation there was a significant increase in rat hypothalam ic GHRH mRNA expression compared with time-matched control samples. Hypotha lamic GHRH mRNA levels were not significantly different from control values after 1 or 2 h of recovery after 8 h of sleep deprivation or after 2 h of recovery after 12 h of sleep deprivation. In control animals, variations in hypothalamic GHRH mRNA levels were observed. GHRH mRNA expression was sign ificantly higher in the afternoon than at dark onset or during the dark per iod. SRIH mRNA levels were significantly suppressed at the termination of a n 8-h sleep deprivation period and were significantly higher after dark ons et than in the morning. The alterations in GHRH and SRIH mRNA expressions a fter sleep deprivation and recovery support the notion that GHRH plays an i mportant role in sleep homeostasis and suggest that these neuropeptides may interact reciprocally in modulating sleep as they do in the control of gro wth hormone secretion.