Effects of plant ingestion in rats determined by the conditioned taste aversion procedure

Abstract

The conditioned taste aversion procedure was used to compare the aversive effects produced by 40 plants (mostly common household varieties) to those of amphetamine, lithium chloride and ethyl alcohol. Test substances (plant homogenates or drug solutions) were given to rats by force-feeding 5 min after the subjects' first exposure to 0·1% saccharin solution, which was available for 15 min from a water bottle. The comparison of the consumption of saccharin solution, two days after test substance administration, to the initial saccharin consumption was taken as a measure of the aversive effects produced by the test substance, e.g. greater suppression of saccharin intake indicating greater aversive properties. Dose dependent suppression of saccharin intake was obtained with most of the substances tested at more than one concentration. Administration of Pokeberry seeds, Japanese Yew, Norfolk Island Pine and Oleander leaves suppressed saccharin intake more than ethyl alcohol. The rest of the plants tested produced less conditioned aversion than ethyl alcohol. Some plants which are frequently called poisonous (Poinsettia, Philodendron and Dieffenbachia) were not particuarly effective in producing conditioned taste aversion. Good correlation existed between suppression of saccharin intake produced by the three drugs tested and their approximate acute lethal doses in rats and humans, suggesting that the conditioned taste aversion procedure may indicate the approximate acute lethality of these substances. Good correlation was also found between the dry weight of the plants and the suppression of saccharin intake.