GI signaling

Conditioned taste aversion often depends on non-toxic neural or chemical signals. For example, copper sulfate or hypertonic solutions in the gut can stimulate enterochromaffin cells (leading to emesis and CTA), presumably in the absence of tissue damage per se. Likewise, postabsorptive effects of toxins on behavior may be indirect (e.g. lithium is detected by neurons in the area postrema and induces a CTA, in the absence of toxic effects elsewhere in the body.) And of course completely non-toxic stimuli such as whole body rotation easily induce nausea and CTA. Perhaps the best example of tissue-damage induced CTA is ionizing radiation, which damages mast cells resulting in histamine release that induces CTA.