dokomo is spot on in regards to this issue. he is 100% correct.
Sweet P, sorry to be the bearer of bad news but you are wrong.
(Meth)Amphetamine causes loss of dopaminergic axons in the substantia nigra. So, while the cell body does remain intact, it cannot propagate action potentials to the dendrites of subsequent postsynaptic neurons. This damage is IRREVERSIBLE.
....I know what I am talking about. Chronic abuse of these drugs also does one more thing that is incredibly detrimental. Over time, the amphetamine will actually reverse the action of the proton pump in the Vesicular Monoamine Transporter. This basically causes vesicular dopamine to become synaptic and leaves amphetamines as the sole occupant of dopaminergic vesicles. Also, the proton gradient is lost; as such, it is impossible for the vesicles to pump dopamine across their membrane, as the gradient which performed this function has been lost. The net result of this is a brain which looks very similar to that of a Parkinson's patient; almost nonexistent vesicular dopamine, downgraded postsynaptic dopamine receptors, and a complete loss of dopaminergic axons in the Substantia Nigra.
Please trust me on this issue, as I have performed a plethora of research in this area for the NIH and the NIDA.
Best of luck