HTR2A and cyclic hematopoiesis: Nevertheless, adding to support that 5-HT2 receptors are the predominant mediators of CH psychoactive effects are the observations that 5-HT2A knockout mice do not exhibit behaviors, such as the head-twitch response (HTR; Gonzalez-Maeso et al., 2007; Hanks and Gonzalez-Maeso, 2013), typically elicited by CH.