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A great amount of research has been devoted to understanding the way cocaine produces its pleasurable effects, and the reasons it is so addictive. One mechanism is through its effects on structures deep in the brain. Scientists have discovered regions within the brain that, when stimulated, produce feelings of pleasure. One neural system that appears to be most affected by cocaine originates in a region, located deep within the brain, called the ventral tegmental area (VTA).
Nerve cells originating in the VTA extend to the region of the brain known as the nucleus accumbens, one of the brain's key pleasure centers. In studies using animals, for example, all types of pleasurable stimuli, such as food, water, sex, and many drugs of abuse, cause increased activity in the nucleus accumbens.
Cocaine in the brain - In the normal communication process, dopamine is released by a neuron into the synapse, where it can bind with dopamine receptors on neighboring neurons. Normally dopamine is then recycled back into the transmitting neuron by a specialized protein called the dopamine transporter. If cocaine is present, it attaches to the dopamine transporter and blocks the normal recycling process, resulting in a build-up of dopamine in the synapse which contributes to the pleasurable effects of cocaine.
Researchers have discovered that, when a pleasurable event is occurring, it is accompanied by a large increase in the amounts of dopamine released in the nucleus accumbens by neurons originating in the VTA. In the normal communication process, dopamine is released by a neuron into the synapse (the small gap between two neurons), where it binds with specialized proteins (called dopamine receptors) on the neighboring neuron, thereby sending a signal to that neuron. Drugs of abuse are able to interfere with this normal communication process. For example, scientists have discovered that cocaine blocks the removal of dopamine from the synapse, resulting in an accumulation of dopamine. This buildup of dopamine causes continuous stimulation of receiving neurons, probably resulting in the euphoria commonly reported by cocaine abusers.
As cocaine abuse continues, tolerance often develops. This means that higher doses and more frequent use of cocaine are required for the brain to register the same level of pleasure experienced during initial use. Recent studies have shown that, during periods of abstinence from cocaine use, the memory of the euphoria associated with cocaine use, or mere exposure to cues associated with drug use, can trigger tremendous craving and relapse to drug use, even after long periods of abstinence.
The widespread abuse of cocaine has stimulated extensive efforts to develop treatment programs for this type of drug abuse.
One of NIDA's top research priorities is to find a medication to block or greatly reduce the effects of cocaine, to be used as one part of a comprehensive treatment program. NIDA-funded researchers are also looking at medications that help alleviate the severe craving that people in treatment for cocaine addiction often experience. Several medications are currently being investigated for their safety and efficacy in treating cocaine addiction.
In addition to treatment medications, behavioral interventions (particularly cognitive behavioral therapy) can be effective in decreasing drug use by patients in treatment for cocaine abuse. Providing the optimal combination of treatment and services for each individual is critical to successful outcomes.
What is the effect of maternal cocaine use?
The full extent of the effects of prenatal drug exposure on a child is not completely known, but many scientific studies have documented that babies born to mothers who abuse cocaine during pregnancy are often prematurely delivered, have low birth weights and smaller head circumferences, and are often shorter in length.
Estimating the full extent of the consequences of maternal drug abuse is difficult, and determining the specific hazard of a particular drug to the unborn child is even more problematic, given that, typically, more than one substance is abused. Such factors as the amount and number of all drugs abused; inadequate prenatal care; abuse and neglect of the children, due to the mother's lifestyle; socio-economic status; poor maternal nutrition; other health problems; and exposure to sexually transmitted diseases, are just some examples of the difficulty in determining the direct impact of perinatal cocaine use, for example, on maternal and fetal outcome.
Many may recall that "crack babies," or babies born to mothers who used cocaine while pregnant, were written off by many a decade ago as a lost generation. They were predicted to suffer from severe, irreversible damage, including reduced intelligence and social skills. It was later found that this was a gross exaggeration. Most crack-exposed babies appear to recover quite well. However, the fact that most of these children appear normal should not be over-interpreted as a positive sign. Using sophisticated technologies, scientists are now finding that exposure to cocaine during fetal development may lead to subtle, but significant, deficits later, especially with behaviors that are crucial to success in the classroom, such as blocking out distractions and concentrating for long periods of time.
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