From what I understand, once serotonin is depleted enough in the synapse, the serotonin reuptake transporterss begin to bind to dopamine (instead of serotonin),

From what I understand, once serotonin is depleted enough in the synapse, the serotonin reuptake transporterss begin to bind to dopamine (instead of serotonin), and that by itself is toxic to that part of the neuron. To make matters worse, the neuron then converts the uptaken dopamine into hydrogen peroxide, which is VERY toxic to that part of the neuron (the axon terminal), which then causes it to fizzle away. I recall a way around that (other than by just not taking MDMA at all, obviously) is to take an SSRI (like Prozac) at some point after rolling, which would bind to the reuptake transporters, preventing dopamine from doing so.