Purity >98%. Arachidonoyl amides of both amino acids and neurotransmitters such as dopamine have been previously reported in the literature. N-Arachidonoyl-L-serine (ARA-S) is one such recently isolated endocannabinoid with an unusual activity profile. ARA-S does not bind to central cannabinoid (CB1 ) and peripheral cannabinoid (CB2 ) receptors or vanilloid receptor 1 (VR1). Like cannabidiol, ARA-S (5 mg/kg) antagonizes the hypotensive effects of a 10 mg/kg IV bolus of abnormal cannabidiol (Abn-CBD) in an anesthetized rat blood pressure model. However, similar to Abn-CBD, ARA-S relaxes isolated rat mesenteric arteries and abdominal aorta as well as increases phosphorylation of Akt and mitogen-activated protein kinase (MAPK) in HUVEC. The precise mechanisms of action by ARA-S and Abn-DBD in various vascular preparations appears to be different and requires further investigation.