Methiothepin mesylate is primarily used in research settings as a potent serotonin receptor antagonist. It is particularly valuable in studies focusing on the central nervous system, where it helps to elucidate the roles of serotonin receptors in various physiological and pathological processes. Researchers utilize it to investigate conditions such as depression, anxiety, and schizophrenia, as it blocks serotonin receptors, providing insights into their mechanisms. Additionally, it is employed in pharmacological experiments to understand neurotransmitter interactions and to develop potential therapeutic agents targeting serotonin pathways. Its application extends to behavioral studies in animal models, aiding in the exploration of serotonin's influence on mood, cognition, and behavior.