Wikipedia
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 by a metabolite. 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.
However, the effects of the compound on experimental animals appear less encouraging. It has been detected as an apparent designer drug, along with the related 3-chloroamphetamine, which is even more potent as a releaser of dopamine and serotonin but slightly less neurotoxic.
The closely related N-methylated derivative, para-Chloromethamphetamine (CMA), which is metabolised to para-chloroamphetamine in vivo, has neurotoxic properties as well.