Present address: Laboratorio de Neurobiología, Universidad Autónoma de Campeche, Av. Patricio Trueba y de Regil s/n, Col. Buenavista C.P. 24030, Campeche, Campeche, México.
Effects of hypocretin (orexin) neuronal loss on sleep and extracellular adenosine levels in the rat basal forebrain
Article first published online: 9 SEP 2008
© The Authors (2008). Journal Compilation © Federation of European Neuroscience Societies and Blackwell Publishing Ltd
European Journal of Neuroscience
Volume 28, Issue 6, pages 1191–1198, September 2008
How to Cite
Murillo-Rodriguez, E., Liu, M., Blanco-Centurion, C. and Shiromani, P. J. (2008), Effects of hypocretin (orexin) neuronal loss on sleep and extracellular adenosine levels in the rat basal forebrain. European Journal of Neuroscience, 28: 1191–1198. doi: 10.1111/j.1460-9568.2008.06424.x
- Issue published online: 11 SEP 2008
- Article first published online: 9 SEP 2008
- Received 4 March 2008, revised 30 June 2008, accepted 24 July 2008
- basal forebrain;
- REM sleep;
Neurons containing the neuropeptide hypocretin (HCRT, orexin) are localized only in the lateral hypothalamus, from where they innervate multiple regions implicated in arousal, including the basal forebrain. HCRT activation of downstream arousal neurons is likely to stimulate release of endogenous factors. One such factor is adenosine, which in the basal forebrain increases in level with wakefulness and decreases with sleep, and is hypothesized to regulate the waxing and waning of sleep drive. Does loss of HCRT neurons affect adenosine levels in the basal forebrain? Is the increased sleep that accompanies HCRT loss a consequence of higher adenosine levels in the basal forebrain? In the present study, we investigated these questions by lesioning the HCRT neurons with HCRT-2–saporin (HCRT-2–SAP) and measuring sleep and extracellular levels of adenosine in the basal forebrain. In separate groups of rats, the neurotoxin HCRT-2–SAP or saline was administered locally to the lateral hypothalamus, and 80 days later adenosine and sleep were assessed. Rats given the neurotoxin had a 94% loss of HCRT neurons. These rats woke less at night, and had more rapid eye movement sleep, which is consistent with HCRT hypofunction. These rats also had more sleep after brief periods of sleep deprivation. However, in the lesioned rats, adenosine levels did not increase with 6 h of sleep deprivation, whereas an increase in adenosine levels occurred in rats without lesion of the HCRT neurons. These findings indicate that adenosine levels do not increase with wakefulness in rats with a HCRT lesion, and that the increased sleep in these rats occurs independently of adenosine levels in the basal forebrain.