Studied the relationship between increased serotonin (5HT) receptor sensitivity & human aggression. A low, oral dose of meta-chlorophenylpiperazine (MCPP) was administered to 42 patients, including 11 who had attempted suicide (inward aggression). Results showed that patients with a history of suicide attempts did not have significantly greater MCPP-induced cortisol or prolactin release than did normal controls & that MCPP induced hormone release is unrelated to measures of aggression. (40 refs)