Levels, metabolism, and pharmacological activity of anandamide in CB(1) cannabinoid receptor knockout mice: evidence for non-CB(1), non-CB(2) receptor-mediated actions of anandamide in mouse brain.
Anandamide [arachidonylethanolamide (AEA)] appears to be an endogenous agonist of brain cannabinoid receptors (CB(1)), yet some of the neurobehavioral effects of this compound in mice are unaffected by a selective CB(1) antagonist. We studied the levels, pharmacological actions, and degradation of AEA in transgenic mice lacking the CB(1) gene. We quantified AEA and the other endocannabinoid, 2-arachidonoyl glycerol, in six brain regions and the spinal cord by isotope-dilution liquid chromatography-mass spectrometry. The distribution of endocannabinoids and their inactivating enzyme, fatty acid amide hydrolase, were found to overlap with CB(1) distribution only in part. In CB(1) knockout homozygotes (CB(1)-/-), the hippocampus and, to a lesser extent, the striatum exhibited lower AEA levels as compared with wild-type (CB(1)+/+) controls. These data suggest a ligand/receptor relationship between AEA and CB(1) in these two brain regions, where tonic activation of the receptor may tightly regulate the biosynthesis of its endogenous ligand. 2-Arachidonoyl glycerol levels and fatty acid amide hydrolase activity were unchanged in CB(1)-/- with respect to CB(1)+/+ mice in all regions. AEA and Delta(9)-tetrahydrocannabinol (THC) were tested in CB(1)-/- mice for their capability of inducing analgesia and catalepsy and decreasing spontaneous activity. The effects of AEA, unlike THC, were not decreased in CB(1)-/- mice. AEA, but not THC, stimulated GTPgammaS binding in brain membranes from CB(1)-/- mice, and this stimulation was insensitive to CB(1) and CB(2) antagonists. We suggest that non-CB(1), non-CB(2) G protein-coupled receptors might mediate in mice some of the neuro-behavioral actions of AEA.
Di Marzo
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V
Istituto per la Chimica di Molecole di Interesse Biologico, Consiglio Nazionale delle Ricerche, Arco Felice, Italy. vdimarzo@icmib.na.cnr.it
Breivogel
C S
CS
Tao
Q
Q
Bridgen
D T
DT
Razdan
R K
RK
Zimmer
A M
AM
Zimmer
A
A
Martin
B R
BR
D000581:Amidohydrolases / Q000378:metabolism; D000818:Animals; D001095:Arachidonic Acids / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology*; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects / Q000235:genetics; D063385:Cannabinoid Receptor Modulators; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000494:pharmacology; D063388:Endocannabinoids; D005260:Female; D005989:Glycerides / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009928:Organ Specificity; D053284:Polyunsaturated Alkamides; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000172:deficiency / Q000235:genetics*; D000099252:Fatty Acid Amide Hydrolases
D000581:Amidohydrolases; D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D013759:Dronabinol; D063388:Endocannabinoids; D005989:Glycerides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D053284:Polyunsaturated Alkamides; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D000099252:Fatty Acid Amide Hydrolases; C094503:glyceryl 2-arachidonate; C078814:anandamide