Table 1.

Experimental design of combination studies of the uncompetitive NMDA receptor antagonist memantine with either the CB₁ receptor antagonist rimonabant or the cholinesterase inhibitor donepezil. The doses of rimonabant and donepezil were chosen based on our previous delayed radial arm maze study (Wise et al., 2007). Treatments in each experiment were counterbalanced to control for any order effects. Subjects were given a maximum of two tests/week, with at least 48 h between test sessions.

Experiment	Treatment 1	Treatment 2	Treatment 3	Treatment 4
3A: Subthreshold doses
Memantine	0	0.1 mg/kg	0	0.1 mg/kg
Rimonabant	0	0	0.3 mg/kg	0.3 mg/kg
3B: Subthreshold doses
Memantine	0	0.1 mg/kg	0	0.1 mg/kg
Donepezil	0	0	0.1 mg/kg	0.1 mg/kg