HTR5A and post-traumatic stress disorder: Furthermore, administration of meta-chlorophenylpiperzine (mCPP), a 5-HT2C receptor agonist, resulted in acute anxiety, panic attacks, and PTSD symptoms in a subgroup of male combat veterans with PTSD, but not other psychiatric disorders, suggesting a role of the 5-HT system in the pathophysiology of PTSD (Krystal et al., 1996; Krystal & Neumeister, 2009).