We have two things at play here, actually. The dopamine
gives you euphoria
when you use meth
. Normally, the brain also releases dopamine when you are happy: in anticipation of something, or a reward. Meth also stimulates the Central Nervous System (CNS), and does a great job of stimulating your genital area.
While the genitals are buzzing away and you react to the feeling, dopamine is released rewarding you for playing around down there. Nerve stimulation and dopamine euphoria--feel good, and feel good from two different areas of the body.
The only way you are going to cause damage to your dopamine receptors is to keep using meth in a binge-type of situation. If you are doing one shot, or are at least sticking to a small time frame of using meth with any ROA (Route of Administration), when the dopamine neuroreceptors are full, they start shutting down due to the overload (downregulating). Or, if you have used all of the dopamine available, there's nothing to feed the neuroreceptors, and they remain idle.
Only through continued abuse can you damage your dopamine neuroreceptors. Then, if you stop, some of them repair themselves. However, it you have been abusing meth for a long period of time, some of them won't be able to repair.