Rationale: Anticipatory nausea (AN) experienced by chemotherapy patients is resistant to current anti-nausea treatments. In this study, the effect of manipulation of the endocannabinoid (EC) system on a rat model of nausea (conditioned gaping) was determined.
Objective: The potential of cannabidiol (CBD) and the fatty acid amide hydrolase (FAAH) inhibitor, URB597 (URB) to reduce conditioned gaping in rats were evaluated.
Materials and methods: In each experiment, rats received four conditioning trials in which they were injected with lithium chloride immediately before placement in a distinctive odor-laced context. During testing, in experiment 1, rats were injected with vehicle (VEH), 1, 5 or 10 mg/kg CBD 30 min before placement in the context previously paired with nausea and in experiment 2, rats were injected with VEH, 0.1 or 0.3 mg/kg URB 2 h before placement in the context. Additional groups evaluated the ability of the CB(1) antagonist/inverse agonist, SR141716A, to reverse the suppressive effects of URB. Experiment 3 measured the potential of URB to interfere with the establishment of conditioned gaping.
Results: When administered before testing, CBD (1 and 5, but not 10 mg/kg) and URB (0.3, but not 0.1 mg/kg) suppressed conditioned gaping. The effect of URB was reversed by pre-treatment with the CB(1) antagonist/inverse agonist, SR141716A. When administered before conditioning, URB also interfered with the establishment of conditioned gaping.
Conclusions: Manipulations of the EC system may have therapeutic potential in the treatment of AN.