Addictive substances — including heroin and prescription painkillers — send dopamine levels surging in the small localized area of the brain called the nucleus accumbens, the main reward center that is responsible for the temporary, pleasant sensation and reinforcing effects of substances of abuse.
Addicted persons and first-time users get the high that correlates with the dopamine surge. The more dopamine is released, the greater perception of the reward. Users increasingly crave the drug, and the act of turning to it becomes a conditioned response. Some people will develop the compulsion and loss of control to keep taking the drug, a behavior that defines addiction today.
What Happens to the Brain as an Addiction Forms?
Researchers now postulate that addiction, including heroin addiction, requires two things. First is a genetic vulnerability, which may include the quantity of dopamine receptors in the brain. Initially excessive dopamine receptor activation may lead to more reinforcing effects of the drugs. The brain, however, is not wired to handle the intense high that drugs produce. Over time, a shut-off mechanism takes over, reducing the number of receptors in the brain that receive dopamine signaling. Consequently, with addiction and compulsive drug use, the ability of the brain to generate a sense of pleasure decreases to the point where the addicted person who initially took heroin to feel good may very well be taking the drug to stay afloat and avoid feeling worse.
Second, repeated assaults and hijacking of dopamine circuitry on areas of the brain responsible for motivation, decision-making, memory and new learning abilities appear to fundamentally alter the brain’s hardwiring. This may further accelerate compulsive drug use, poor decision making, and impaired impulse control.
Recovering from Heroin Abuse
Fortunately, the brain can heal after discontinuing heroin use. How a person recovers from heroin addiction depends on several neurochemical and environmental factors.
In early recovery, the opioid receptors may be “burned out,” and there may be an exhaustion of dopamine in the current brain circuitry. The dopamine circuitry may remain blunted for some time, even months into sobriety. Recovery may take years to possibly re-establish dopamine homeostasis in the brain, explaining why people addicted to heroin may face intense difficulties in staying clean. Dopamine depletion in key neuro-circuits in the brain leads to challenges in consolidating new learning, motivation, and experiences that accompany attempts at changing behavior.
Addicted persons may perceive and appreciate that only “the drug of choice” may elevate dopamine levels high enough to experience any kind of pleasure, and that ordinary rewards of daily life may have little effect on the recovering brain. Further research is needed in developing better relapse prevention programming that can change this hardwiring and a possible vaccine that can blunt the initial dopamine surge that accompanies first-time heroin use.