Like, taking meth causes some destruction of neurotransmitters and (I think) meth tollerance happens by the destruction of neurotransmitter sites, leaving less working cites/neurotransmitters, resulting in a need to take more to achieve the desired effect, which of course, destroys more in the brain.
With opioids, tolerance forms when the body realizes there are wayy more neurotransmitters than normal. When someone is strung out and constantly taking opioids, the body says "well, this is the new normal" and adjusts the amount/sensitivity of the binding sites to try and achieve an equilibrium. The body/brain always "wants" to be in equilibrium and makes changes to do this. So now, the normal dose starts to loose effectiveness because the body/brain is making changes to incorporate the new flood of neurotransmitters (or something that acts like neurotransmitters) into the "normal" function. The body doesn't "like" being high and always shoots for "normal"
The difference, is when one quits using opioids, the user enters withdrawal because all of a sudden the neurotransmitters the body was counting on being there just disappeared. OH NO! But then the body begins to change again, working to correct the balance and to get back to "normal" where the neurotransmitters work as they should. Eventually, the opioid dependent person would get back to a state of equilibrium, where their nervous system operates pretty much as it should. The point is, after stopping opioid use, given enough time, one can make a recovery and regain the function from before for the most part.
With Meth and other amphetamine type stimulants (and stuff like MDMA, Cathinones, Synthetic cannabinoids, and a whole ass load of other chemicals), the mode of tollerance is the actual destruction of neurotransmitters and their binding sites or their production site. Meaning once someone quits using them, and the initial adjustment period the body goes through, the body/brain will have a reduced capacity to function as normal. The action of the brains functions will have been permanently changed. You know how some meth users who went balls to the wall and did a full year of near constant amphetamine psychosis never really seem to be themselves even after getting sober? its because their brain has been damaged and no longer functions correctly. Some people can get stuck in permanent psychosis (which is rare), but after "quitting" the users brain functioning will be altered in a negative way.
If you OD on heroin and stop breathing for 6 minutes, you'll have brain damage, but if someone uses diamorphine for a long time and stops, eventually they will return to normal. With toxic and neurotoxic drug use, after cessation, the body generally can not and will not return to "normal" and will be damaged in some capacity more or less permanently.
Of course, with opioids I've never really felt "back to normal" after quitting because I remember how good they were, and I always thing "how much better [inset activity here] would be if I was high", and some activities seem trivial because they don't really tickle me the way they did before I used. All of this is because of conditioning the response to opioids in my mind. I havent "damaged" my brain, but I've conditioned myself to value the opioid reward over a whole lotta things, and after I quit, going to work feels more tedious because I've conditioned myself to think that everything needs opioids to be enjoyed, done well, done right, etc. Its not brain tissue damage, but more of a psychologiccal phenomenon where I trained myself to value one thing above all else. And that one thing happened to be very illegal and very expensive.
Thats where all the problems with opioids come from; they're very expensive, very illegal, and very very very fun. Once you've started the process of integrating opioids into your bodys equilibrium, It doesn't really seem possible (at that moment) to rebuild without it, because, as we all know, they feel really, really good, and seem to answer anyone's problems they have for some time. Add to this the fact that any user doesn't start to experience serious withdrawal and dependancy symptoms until they've more or less completely integrated it into their life and convinced themselves that they "can" use, you have the crazy addictive problems opioids and heroin bring around.
Then add that its very illegal, and now black markets can make ass loads of money selling the very illegal thing. Thats also incentive to "stretch" the supply out as much as possible to maximize profit (and to make supply last longer). THIS is where the main danger with heroin/opiates is. Dealers importing 1kg of diamorphine into the U.S in their ass, sold to dealer 1 who cuts it 2 to 1 with laxitives and packs it inside a loaf of moldy bread to sell to dealer 2 who cuts it 3 to 1 with benadryl, who sells it to street dealer 3 who cuts it 8 to 1 with talcum powder and some other white powder he tinks looks pretty close to what heroin should, and finally sells it to the final street dealer who bought 500mg of fentanyl online and believes adding 2mg to the heroin will stretch his supply out from 100 bags to 1000 bags. From the start, the business takes whatever amount they start with, and pump it through a pipeline that inflates the price of it by, like, 10,000X
Also, I give my sincere apology for more or less completely de-railing this thread from drug buying sketchiness to explanations of toxicity with respect for drugs. Sorry justtakethat
