Mouse brain microsomes contain an amidase that catalyzes the hydrolysis of N-arachidonylethanolamide to arachidonic acid and ethanolamine. The enzymatic activity is dependent on the protein concentration of the microsomes and observed over a wide range of pH, 7.4 to 9.5. Kinetic analysis indicated that K(m) (microM) and Vmax (nmol/min/mg protein) were 17.7 +/- 4.1 and 1.81 +/- 0.32, respectively. Cannabidiol (CBD), cannabinol (CBN) and delta 9-tetrahydrocannabinol (delta 9-THC) significantly inhibited the hydrolysis of the amide by mouse brain microsomes. At a concentration of 160 microM, the inhibitory potency decreased in the following order, CBD (66%) > CBN (46%) > delta 9-THC (31%).