Head-twitch response
The head-twitch response (HTR) is a rapid side-to-side head movement that occurs in mice and rats after the
5-HTP, fenfluramine, 1-Methylpsilocin, Ergometrine, and 3,4-di-methoxyphenethylamine (DMPEA) can also produce head twitch and do stimulate serotonin receptors, but are not hallucinogenic in humans.[6][7] This means that while the head twitch response can be a useful indicator as to whether a compound is likely to display hallucinogenic activity in humans, the induction of a head twitch response does not necessarily mean that a compound will be hallucinogenic, and caution should be exercised when interpreting such results.[8]
