Levels, Metabolism, and Pharmacological Activity of Anandamide in CB₁ Cannabinoid Receptor Knockout Mice

Abstract

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 Ϫ/Ϫ), the hippocampus and, to a lesser extent, the striatum exhibited lower AEA levels as compared with wild-type (CB 1 ϩ/ϩ) 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 Ϫ/Ϫ with respect to CB 1 ϩ/ϩ mice in all regions. AEA and ⌬ 9 -tetrahydrocannabinol (THC) were tested in CB 1 Ϫ/Ϫ 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 Ϫ/Ϫ mice. AEA, but not THC, stimulated GTP␥S binding in brain membranes from CB 1 Ϫ/Ϫ 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 neurobehavioral actions of AEA. Key Words: CannabinoidAnandamide -2-Arachidonyl glycerol-Tetrahydrocannabinol-CB 1 receptor knockout-C57BL/6 mouse.

The genetic versus pharmacological invalidation of the cannabinoid CB1 receptor results in differential effects on ‘non-associative’ memory and forebrain monoamine concentrations in mice

“…Here, rimonabant potentiated psychostimulant-sensitization and increased anxiety whereas the genetic invalidation of the CB 1 receptor had opposite effects and reduced behavioral sensitization and failed to influence fear and anxietyrelated behaviors. Thus, our data supports the assumption of a specific rimonabantsensitive cannabinoid receptive site that is different from the 'classical' CB 1 receptor (Di Marzo, Breivogel, Tao, Bridgen, Razdan, Zimmer, Zimmer & Martin, 2000) which, under physiological conditions, seems to be involved in the inhibitory control of the acquisition but not retention of non-associative learning.…”

Chronic exposure to cannabinoids during adolescence causes long‐lasting behavioral deficits in adult mice

“…Adolescence covers a developmental period of psychosocial, social and biological changes. Under normal physiological conditions in adult mice, CB1 receptors and the levels of endocannabinoid AEA and 2‐AG are abundant in the hippocampus (Di Marzo et al , 2000), a crucial structure involved in learning and memory (for review, see Zanettini et al , 2011). …”

Mass‐Spectrometric Identification of Anandamide and 2‐Arachidonoylglycerol in Nematodes

“…Both pharmacological and biochemical data suggest the existence of non-CB 1 non-CB 2 cannabinoid receptors, which may be activated, at least in vitro, by physiologically relevant concentrations of AEA [5]. Di Marzo et al [5] studied levels of AEA in transgenic mice that were lacking the CB 1 gene, and suggested that non-CB 1 and non-CB 2 G protein-coupled receptors might mediate some of the neurobehavioral actions of AEA in mice. Furthermore, Zygmunt et al [6] found that AEA activates vanilloid TRPV1 receptors [4 -6].…”