A C to A transversion was introduced at coding nucleotide 385 (c.385C>A) in exon 3. The FRT site flanked neomycin resistance gene cassette that was inserted was subsequently removed through flp-mediated recombination. The mutation results in the substitution of a conserved proline at amino acid position 129 with a threonine residue (p.P129T). This mimics a polymorphism found in humans where it renders the enzyme susceptible to increased proteolytic degradation. Western blot analysis revealed an allele dose-dependent decrease in protein expression levels in forebrain homogenates from heterozygous and homozygous mutant mice relative to wild-type controls. Hydrolytic activity was reduced while anandamide (AEA) levels were increased in mutant brain homogenates relative to wild-type controls.