In the present study, we investigated the consequences of inhibiting eCB catabolic enzymes on anxiety-like behavior in the marble burying test. Specifically, we tested the effects of pharmacological inhibition of FAAH or MAGL, as well as Δ9-tetrahydrocannabinol (THC) and the benzodiazepine diazepam, on marble burying and locomotor activity. As reported previously (Broekkamp et al., 1986; Njung'e and Handley, 1991b), diazepam dose-dependently decreased marble burying. The FAAH inhibitor PF-3845 and the MAGL inhibitor JZL184 decreased marble burying, at doses that did not affect locomotor activity, suggesting that eCBs may reduce compulsive or anxiety-like behavior in the marble burying test. The observation that rimonabant completely blocked reductions in marble burying, following FAAH or MAGL inhibition, indicates a CB1 receptor mechanism. The overall pattern of marble burying in response to THC indicated sedative effects in the range of doses tested. It is noteworthy that, as in previous studies, FAAH inhibition had no effect on locomotor activity.
