Ondansetron and delta-9-tetrahydrocannabinol interfere with the establishment of lithium-induced conditioned taste avoidance in the house musk shrew (Suncus murinus)

Considerable evidence suggests that rats can learn to avoid a taste in the absence of nausea. The current experiments evaluated the potential of the antiemetic agents, ondansetron (OND) and delta-9tetrahydrocannabinol (THC), to interfere with lithium chloride (LiCl)-induced taste avoidance in the house musk shrew, Suncus murinus, an insectivore that, unlike rats, is capable of vomiting. At a dose that did not modify saccharin (Experiment 1) or sucrose (Experiment 2) intake, OND prevented the establishment of LiCl-induced taste avoidance in the shrew. A low dose of THC (1 mg/kg), which did not modify sucrose intake during conditioning, also prevented the establishment of LiCl-induced taste avoidance in the shrew. Higher doses of THC were also effective, but they also suppressed sucrose consumption during conditioning. These results suggest that nausea is a necessary component of the unconditioned stimulus for the establishment of conditioned taste avoidance in the shrew, unlike the rat, which does not vomit when injected with a toxin.