Organophosphate agent induces ADHD-like behaviors via inhibition of brain endocannabinoid-hydrolyzing enzyme(s) in adolescent male rats.

Anticholinergic organophosphate (OP) agents act on the diverse serine hydrolases, thereby revealing unexpected biological effects. Epidemiological studies indicate a relationship between OP exposure and development of attention-deficit/hyperactivity disorder (ADHD)-like symptoms, whereas no plausible mechanism for the OP-induced ADHD has been established. The present investigation employs ethyl octylphosphonofluoridate (EOPF) as an OP-probe which is an extremely potent inhibitor of endocannabinoid (EC, anandamide and 2-arachidonoylglycerol)-hydrolyzing enzymes: i.e., fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL). Ex vivo experiment shows that EOPF treatment decreases FAAH and MAGL activities and conversely increases EC levels in rat brain. Subsequently, EOPF (treated intraperitoneally once at 0, 1, 2, or 3 mg/kg) clearly induces ADHD-like behaviors (in elevated plus-maze test) in both Wistar and spontaneously hypertensive rats. The EOPF-induced behaviors are reduced by a concomitant administration of cannabinoid receptor inverse agonist SLV-319. Accordingly, EC system is a feasible target for OP-caused ADHD-like behaviors in adolescent rats.