Tryptamine, infused intravenously in man, facilitates the patellar reflex, dilates pupils and elevates blood pressure. It also causes changes in vision and hearing, as well as nausea, vomiting, dizziness, sweating and heaviness of body. These changes are similar to those produced by LSD-like hallucinogens and are consistent with the hypothesis that LSD-like hallucinogens interact with...