No effect of chronic fenfluramine on the P300 component of the event-related potential

Five autistic children were administered a visual version of the oddball paradigm under both drug (chronic fenfluramine) and placebo conditions. The P300 component of the event-related potential (ERP) was not affected by fenfluramine, although the drug significantly lowered blood concentrations of serotonin. It was concluded that serotonin as a neurotransmitter does not play a major role in production of P300. This conclusion fits with the facts that: (1) the general functional role of serotonin in the nervous system is to globally inhibit the overt expression of behavior, and (2) P300 is generally insensitive to response selection processes.