It's unlikely that the damage can be reversed, once it occurs. The damage is not to the DA receptors, though. Meth, like all the amphetamines, acts by releasing the neurotransmitter from the cells independently of the biological release mechanism, and by preventing its reuptake back into the cell. That latter is the primary mechanism of dopamine and related neurotransmitter inactivation. One biological adaptive mechanism is that the number of receptor proteins embedded in adjacent cells will decrease in response to the extracellular overload of transmitter, but this decrease takes considerable time and is not in proportion to the increased dopamine availability caused by the drug. The enzymes that usually take care of the rest are saturated and also do not keep up. The damage downstream may or may not be corrected by biological adaptation; my opinion is that these, too, are beyond saturation. Any recovery will take a long, long time.
Remember that the only "brain" cells that regenerate are actually in the nasal cavity, not in the cerebrum. So if cells die as a consequence of this and if systems that normally might take over from trauma are also damaged, recovery prognosis is dim. It's extremely complex, and no treatment can address that.
