Retinas were homogenized in RIPA buffer (150 mM NaCl, 20 mM Tris, pH 8.0, 1% NP-40, 0.1% SDS, 1 mM EDTA), supplemented with a protease inhibitor mixture (aprotinin, leupeptin, pepstatin [1 μg/mL] and phenylmethylsulfonyl fluoride [0.2 mg/mL]; Roche Applied Science, Laval, QC, Canada). Thirty micrograms of protein per sample of the homogenate were resolved by electrophoresis on a 10% SDS-polyacrylamide gel, transferred onto a nitrocellulose membrane, blocked with 5% skim milk, and incubated overnight with antibodies directed against CB2R, CB1R, N-acyl phosphatidyethanolamine phospholipase D (NAPE-PLD), diacylglycerol lipase α (DAGLα), fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MGL), or glyceraldehyde 3-phosphate dehydrogenase (GAPDH), the latter serving as a loading control. The blots were exposed to the appropriate horseradish peroxidase–coupled secondary antibodies (Jackson Immunoresearch Laboratories, West Grove, PA). Detection was carried out by using homemade ECL Western blot detection reagents (final concentrations: 2.5 mM luminol, 0.4 mM p-coumaric acid, 0.1 M Tris-HCl pH 8.5, 0.018% H2O2).