I tried to search in textbooks and papers but barely found any concrete answer to which exact mechanism is behind non-intuitive transition from pain to pleasure. Does it have something to do with:
- just the effect of dopamine (once the pain is administered, endorphins inhibit GABA and increase dopamine release)?
- initially decreased levels of beta-endorphins in the brain, so that pain increases DA release as in (1) and even this small release is enough to feel the pleasure? And, as in people who are prone to self-harm, is it some kind of a "desperate attempt to artificially set the body to survival mode in order to mobilize the last reserves of the endogenous opioid system"?
- lower sensitivity (to pain?) in such people?
- some other explanations?
If someone have the answer or ran into papers addressing this question, I would be grateful!