There are two main reasons why heroin addicts continue to use in spite of negative consequences. First of all, when heroin addicts use heroin, it makes them feel good, and secondly, when they stop using heroin, it makes them feel bad. At its core, this may be a tad over simplistic, but that doesn’t mean it’s wrong. For the sake of clarification, we will expand upon this premise in the following paragraphs.
The primary effects of heroin
Heroin consumption activates opioid receptors in three main areas of the brain. Each area produces unique responses. Heroin intoxication is simply a melding of these three responses; euphoria, relaxation and pain relief.
Pleasure has a distinct signature, which is the release of “dopamine.” How this comes about is fascinating. Heroin goes into the brain and binds to and activates opioid receptors atop neurons within the ventral tegmental area (VTA) where the dopamine is stored. As soon as those opioid receptors activate, the neurons that hold the dopamine begin releasing it into the nucleus accumbens (NA). The released Dopamine starts bumping into and binding with dopamine receptors on other neurons, which ultimately creates the sensation of pleasure. So it’s a three step process, first you have Dopamine being released, then Dopamine connects to other neurons in the NA and then you have the perception of pleasure. Dopamine is so consistently tied to pleasure that the NA has been dubbed the pleasure center of the brain.
You could say, in all honesty, that human beings are dopamine machines. Dopamine drives the mind, to control the body, to do things. When a person wants sex, he or she, in fact, wants dopamine. On the other hand, heroin rewards are much different than natural rewards. For one thing, natural dopamine rewards only come from effort or after a delay, but heroin provides a powerful shortcut, and more importantly, it produces more dopamine than any naturally occurring event.
Another part of the brain called the locus coeruleus (LC) keeps us awake and breathing. When heroin is administered, it activates opioid receptors in the LC, thus suppressing norepinephrine production, which relaxes the muscle groups that keep us awake and breathing.
When we physically injure ourselves our body sends a signal to the dorsal horn section of the spine to release Substance P (SP), which then ascends up the spine into the brain where it is recognized as pain. What heroin and other opioids do is descend from the brain stem into the dorsal horn, where they attach to opioid receptors, which modulates SP, thus slowing the rate at which SP can reach the brain. Less SP means less pain. When heroin is taken in large doses, very little if any SP ascends into the brain. The result being the sensation of a completely pain free body, which the brain recognizes as a healthy state. Heroin and other opioids dupe the brain into believing that these drugs improve survivability.
Heroin effects on behavior
Heroin stimulates the reward circuitry in the mid-brain by increasing dopamine. It also short circuits the punishment circuit in the brain-stem and spinal cord. The combination of the two is known as the the “duality of heroin” and this is what makes heroin the most powerful recreational drug in history.
Pleasure is the mechanism that evolution has developed to encourage us to eat, get married, buy a house, etc. When action is possible, pleasure is very often the goal. When someone uses heroin they experience intense pleasure i.e. euphoria. The brain says, “oh great, let’s do this again.”
Action is necessary to respond to danger and when we are confronted by a threat, we have three options: flee, freeze, or fight. If we choose incorrectly pain is often the result. However, when someone quits heroin they’re basically in pain. The brain perceives this situation as a bad decision and the brain’s response is to get high again.
Why can’t heroin addicts quit?
The reward circuitry and the punishment circuitry can be said to supply most of the necessary motivation for most human behaviors. These two systems encourage people to behave so as to suppress their instinctive impulses and avoid pain. Since pleasure and pain are the evolutionary mechanisms used to survive, the typical heroin addict brain equates heroin use with survival (pleasure) and quitting heroin with death (pain).