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Ghrelin-induced sleep responses in ad libitum fed and food-restricted rats
E Szentirmai1, I Hajdu, F Obal
1Department of Physiology, A. Szent-Györgyi Medical and Pharmaceutical Center, University of Szeged, Szeged, Hungary.
Brain Research
|April 25, 2006
Summary
Ghrelin, a peptide regulating food intake, was found to suppress sleep and increase activity and feeding when administered centrally in rats. These findings suggest ghrelin integrates feeding, metabolism, and sleep regulation.
Area of Science:
- Neuroscience
- Endocrinology
- Sleep Research
Background:
- Ghrelin is an endogenous peptide hormone and the primary endogenous ligand for the growth hormone secretagogue receptor.
- Ghrelin plays a crucial role in regulating food intake and is involved in a hypothalamic feeding regulatory circuit alongside neuropeptide Y (NPY) and orexins.
- Orexins and NPY are also known to influence sleep-wake regulation, indicating a potential link between feeding and sleep mechanisms.
Purpose of the Study:
- To investigate the effects of central ghrelin administration on sleep responses, motor activity, and feeding behavior in rats.
- To determine if ghrelin's effects on sleep and activity differ between free-feeding and food-restricted conditions.
- To explore ghrelin's role in the integration of feeding, metabolism, and sleep regulation.
Main Methods:
- Central administration of varying doses of ghrelin (0.2, 1, or 5 microg) to rats under free-feeding conditions.
- Administration of a 1 microg dose of ghrelin to feeding-restricted rats.
- Recording of sleep parameters (NREMS, REMS), motor activity, and food/water intake following ghrelin administration at light or dark onset.
Main Results:
- Ghrelin administration suppressed both non-rapid-eye-movement sleep (NREMS) and rapid-eye-movement sleep (REMS) during the initial hours after light onset.
- Ghrelin induced increased behavioral activity, including feeding, exploring, and grooming, and stimulated food and water intake following light onset injection.
- Ghrelin also suppressed NREMS and REMS at dark onset, though less markedly than at light onset, and a secondary NREMS increase was observed later. In restricted rats, ghrelin suppressed NREMS and REMS.
Conclusions:
- Ghrelin administration significantly impacts sleep architecture, generally suppressing NREMS and REMS, particularly when given during the light period.
- Ghrelin stimulates feeding and motor activity, suggesting a role in the immediate behavioral responses to the peptide.
- The findings support the hypothesis that ghrelin is involved in integrating the complex regulatory processes of feeding, metabolism, and sleep.
