Yes they do but it takes time. Sometimes it can be a few months or years before the brain really goes "back to normal" if there is such a thing. In the beginning you really have to take it one minute, hour, or day at a time.
I would recommend NA or AA if you find that you can't stay stopped on your own. Be careful. I rode the opiate train right into an abyss and it been almost impossible to claw my way back out. The only thing that hasn't happened yet is death or prison. But everything else that comes with this addiction (stealing, bankruptcy, near arrests, loosing family and friends, health problems, suicidal depression, etc.) DID eventually happen to me in two years of being an addict.
Take this seriously before you can't go back.