Anandamide enhances extracellular levels of adenosine and induces sleep: an in vivo microdialysis study.
OBJECTIVE
The principal component of marijuana, delta-9-tetrahydrocannabinol increases sleep in humans. Endogenous cannabinoids, such as N-arachidonoylethanolamine (anandamide), also increase sleep. However, the mechanism by which these molecules promote sleep is not known but might involve a sleep-inducing molecule such as adenosine. Microdialysis samples were collected from the basal forebrain in order to detect levels of adenosine before and after injection of anandamide.


METHODS
Rats were implanted for sleep studies, and a cannula was placed in the basal forebrain to collect microdialysis samples. Samples were analyzed using high-performance liquid chromatography.


METHODS
Basic neuroscience research laboratory.


METHODS
Three-month-old male F344 rats. At the start of the lights-on period, animals received systemic injections of dimethyl sulfoxide (vehicle), anandamide, SR141716A (cannabinoid receptor 1 [CB1] antagonist), or SR141716A and anandamide. One hour after injections, microdialysis samples were collected (5 microL) from the basal forebrain every hour over a 20-minute period for 5 hours. The samples were immediately analyzed via high-performance liquid chromatography for adenosine levels. Sleep was also recorded continuously over the same period.


RESULTS
Anandamide increased adenosine levels compared to vehicle controls with the peak levels being reached during the third hour after drug injection. There was a significant increase in slow-wave sleep during the third hour. The induction in sleep and the rise in adenosine were blocked by the CB1-receptor antagonist, SR141716A.


CONCLUSIONS
Anandamide increased adenosine levels in the basal forebrain and also increased sleep. The soporific effects of anandamide were mediated by the CB1 receptor, since the effects were blocked by the CB1-receptor antagonist. These findings identify a potential therapeutic use of endocannabinoids to induce sleep in conditions where sleep may be severely attenuated.
Murillo-Rodriguez
Eric
E
Neurology Department, Harvard Medical School & VA Medical Center, West Roxbury, Mass 02132, USA.
Blanco-Centurion
Carlos
C
Sanchez
Cristina
C
Piomelli
Daniele
D
Shiromani
Priyattam J
PJ
D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001095:Arachidonic Acids / Q000494:pharmacology* / Q000627:therapeutic use; D063385:Cannabinoid Receptor Modulators / Q000494:pharmacology* / Q000627:therapeutic use; D002851:Chromatography, High Pressure Liquid; D004567:Electrodes, Implanted; D004569:Electroencephalography; D063388:Endocannabinoids; D005625:Frontal Lobe / Q000502:physiology; D007267:Injections; D008297:Male; D017551:Microdialysis; D009778:Occipital Lobe / Q000502:physiology; D053284:Polyunsaturated Alkamides; D051381:Rats; D012890:Sleep / Q000187:drug effects*; D007319:Sleep Initiation and Maintenance Disorders / Q000188:drug therapy*; D012895:Sleep, REM / Q000502:physiology
D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D053284:Polyunsaturated Alkamides; D000241:Adenosine; C078814:anandamide