What you say about Dopamine levels make no sense. You are comparing apples to oranges. Yes, opiate impact the dopamine neurotransitters, but they don't INCREASE the production of them; rather, they DECREASE the production as the feedback loop from the receptors to the production system are fooled by the optiates blocking the receptors.

Naturally increasing neurotransmitters (taking 5HTP for boosting serotonin production) won't have the effect of narcotics, because there's no drug artificially blocking the receptors (which in turn increases the dopamine in the synapse..THAT causes the high from opiates).

According to what you are saying, the production of additional Dopamine will fill the receptors...you're right, that will reduce pain. However, the dopamine production will decrease because the feedback look is telling the production system that there is too much dopamine present - stop producing more dopamine. In opiate users, this marks the beginning of tolerance, since the system continues to adapt and build tolerance to the outside agent (the opiate). Chronic pain relief from natural endorphins and dopamine production is not possible, since the system will adapt, and reduce neurotransmitter levels. What you say may be true with short term pain relief, but that doesn't help with those suffering from chronic pain (and it doesn't help those who are rationalizing opiate use with any pain they might have).