N-Arachidonoyl-L-serine-d8 (ARA-S-d8) contains eight deuterium atoms at the 5, 6, 8, 9, 11, 12, 14, and 15 positions. It is intended for use as an internal standard for the quantification of ARA-S (Item No. 10005455) by GC- or LC-mass spectrometry. Arachidonoyl amides of both amino acids and neurotransmitters such as dopamine have been previously reported in the literature.1 ARA-S is one such recently isolated endocannabinoid with an unusual activity profile. ARA-S does not bind to CB1 and CB2 receptors or vanilloid receptor 1. Like cannabidiol (Item No. 90080), ARA-S (5 mg/kg) antagonizes the hypotensive effects of a 10 mg/kg IV bolus of abnormal cannabidiol (Abn-CBD, CAY10429 Item No. 10004259) in an anesthetized rat blood pressure model.2 However, similar to Abn-CBD, ARA-S relaxes isolated rat mesenteric arteries and abdominal aorta, as well as increases phosphorylation of Akt and MAPK in HUVEC.3 The precise mechanisms of action by ARA-S and Abn-DBD in various vascular preparations appears to be different and requires further investigation.WARNING This product is not for human or veterinary use.