Behavioral indications for serotonin receptor hypersensitivity in panic disorder.

Immediate placebo-corrected behavioral responses to m-chlorophenylpiperazine (MCPP), a selective serotonin agonist, are reported in 11 normal controls, 10 patients with panic disorder, and 10 patients with major depression. Whereas the normal and depressed groups showed no noteworthy behavioral response, panic disorder patients became more anxious, depressed, and hostile, and 60% had panic attacks. These data suggest a hypersensitive postsynaptic serotonin receptor system in some panic disorder patients.