High Quality Content by WIKIPEDIA articles! para-Chloroamphetamine (PCA), also known as 4-chloroamphetamine (4-CA), is an amphetamine derivative and monoamine releaser similar to MDMA, but with substantially higher neurotoxicity, thought to be due to the unrestrained release of both serotonin and dopamine as with MDMA itself. It is used as a neurotoxin by neurobiologists to selectively kill serotonergic neurons for research purposes, in the same way that 6-hydroxydopamine is used to kill dopaminergic neurons.