Discriminative stimulus effects of the structurally novel cannabinoid CB1/CB2 receptor partial agonist BAY 59-3074 in...

BAY 59-3074 [3-[2-cyano-3-(trifluoromethyl)phenoxy]phenyl-4,4,4-trifluoro-1-butane-sulfonate] is a structurally novel cannabinoid CB1/CB2 receptor partial agonist with analgesic properties. The present study was performed to confirm its receptor binding profile in a highly sensitive in vivo assay. Rats (n=10) learned to discriminate BAY 59-3074 (0.5 mg/kg, p.o., t-1 h) from vehicle in a fixed-ratio: 10, food-reinforced two-lever procedure after a median number of 28 training sessions. BAY 59-3074 generalized dose-dependently (ED(50): 0.081 mg/kg, p.o.) and the cue was detectable between 0.25 and 4 h after administration. The selective cannabinoid CB1 receptor antagonist SR 141716A [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride] blocked the discriminative effects of BAY 59-3074 (ID50: 1.79 mg/kg, i.p.). Complete generalization was also obtained after i.p. administration of BAY 59-3074 (ED50 value: 0.41 mg/kg), and the reference cannabinoids BAY 38-7271 [(-)-(R)-3-(2-hydroxymethylindanyl-4-oxy)phenyl-4,4,4-trifluoro-1-butanesulfonate, 0.011 mg/kg], CP 55,940 [(-)-cis-3-[2-hydroxy-4(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxy-propyl)cyclohexanol, 0.013 mg/kg], HU-210 [(-)-11-OH-Delta8-tetrahydrocannabinol dimethylheptyl, 0.022 mg/kg], WIN 55,212-2 [(R)-4,5-dihydro-2-methyl-4(4-morpholinylmethyl)-1-(1-naphthalenylcarbonyl)-6H-pyrrolo [3,2,1-ij] quinolin-6-one, 0.41 mg/kg] and (-)-Delta9-tetrahydrocannabinol (0.41 mg/kg). Non-cannabinoids with analgesic properties, such as morphine, amitriptyline, carbamazepine, gabapentin and baclofen, did not generalize to the cue. It is concluded that the discriminative stimulus effects of BAY 59-3074 are specifically mediated by cannabinoid CB1 receptor activation.