Is my understanding of downregulation and upregulation correct?

[prefrontal cortex]

If you're using cocaine, and your brain cells are getting too much dopamine every day, each cell starts closing some doors to protect itself. It downsizes the number of doors or receptors. That's called downregulation.

This leaves your brain cells unable to feel pleasure. Normal life doesn't give you pleasure anymore. With most of the doors gone, only a drug can make you feel pleasure. Now life sucks and only the DRUG makes you feel good. Only when you quit using the drug can your brain cells upsize the number of doors. That is called upregulation.

After staying away from the drug for awhile, your brain cells go back to having the right number of doors or receptors. Your brain heals and you can feel pleasure from life again.

 

[lamia666]

After staying away from the drug for awhile, your brain cells go back to having the right number of doors or receptors. Your brain heals and you can feel pleasure from life again.

I'm afraid it's not that simple I am also interested in this subject, particularly in upregulation of d2 receptors, and would be grateful if someone could shed some more light on it
I will give U an example that simply cutting off a drug for a while doesnt make U come back to previous level of sensivity:
I used to take L-dopa to get rid of anhedonia, apathy, social phobia and enhance libido, (simply: results of low levels of dopamine). I took it several times, (with some additional agents to make it convert to dopamine). The effects were extraordinary, all symptoms of dysthymia vanished, but tolerance has come rapidly. I had to double the dosage every time I took it, and after 3 weeks the effect was gone no matter how high dosage I took. I think I have killed all of the receptors :-((
I stopped using L-dopa, and tried to come back to using it after couple of weeks, then couple of months, but it didn't work ever since.