(Left panels) Dose-effect functions for the selective FAAH inhibitors URB597 (closed diamond, n = 3) and AM4303 (closed circle, n = 3) in subjects trained to discriminate 0.01 mg/kg AM4054 from vehicle. Abscissae, cumulative dose, log scale; ordinate, percentage of responses on the AM4054-associated lever (top panel), response rate (bottom panel). Symbols left of abscissae break indicate performance during vehicle (V) and AM4054 (AM) control sessions. Points represent averages (±S.E.M.) for the groups of subjects. (Middle panels) Dose-effect functions for the selective MGL-inhibitor AM4301 (closed triangle, n = 4) in subjects trained to discriminate 0.01 mg/kg AM4054 from vehicle. Abscissae, cumulative dose, log scale; ordinate, percentage of responses on the AM4054-associated lever (top panel), response rate (bottom panel). Symbols left of abscissae break indicate performance during V and AM control sessions. Points represent averages (±S.E.M.) for the groups of subjects. (Right panels) Dose-effect functions for nonselective FAAH/MGL inhibitors AM4302 (closed inverted triangle, n = 4) and JZL195 (closed square, n = 3) in subjects trained to discriminate 0.01 mg/kg AM4054 from vehicle. Abscissae, cumulative dose, log scale; ordinate, percentage of responses on the AM4054-associated lever (top right panel), response rate (bottom right panel). Symbols left of abscissae break indicate performance during V and AM control sessions. Points represent averages (±S.E.M.) for the groups of subjects.