Wednesday, March 2, 2011

The Science of Addiction


Cells responsible for passing chemical and electrical signals

come in many shapes and sizes

conduct specialized functions

store memories & control our muscles

communicate through the synapse

transmit messages in the brain


divided into several distinct regions

responsible for performing different functions

made up of about 100 billion neurons and trillions of glia

Reward Pathway

in center of brain

responsible for driving our feelings of motivation, reward and behavior

makes us feel good when we engage in survival behaviors

beneficial behaviors include eating, drinking and sex

connects to several other important areas of the brain

gathers information about what is happening outside of the body

strengthens brain circuits that control desirable behaviors

responsible for trying to make sure you repeat the behavior

a complex network of millions of nerve cells

The release of dopamine gives you a little jolt of pleasure.


electrical signals are translated into chemical signals at the synapse

Nerve cells

communicate at synapses

move from one neuron to another at synapses

Synaptic Cleft

where all the action takes place

The cell sending the message is loaded with vesicles filled with neurotransmitters

The cell receiving the message is coated with dopamine

Electric Impulse

for the release of neurotransmitters into the synaptic cleft

How Signals Are Sent:
An electric impulse is sent down the axon to the terminal area.
Dopamine is released into the synaptic cleft
The dopamine cells then lock into the correct receptors
A second messenger is created and sent into the cell
releases a nerve impulse that is sent to the end of the receiving neutron
the process begins again
Dopamine is released from the receptor and goes back to the original neutron
The dopamine is either reused or broken down

Inhibitory Neurotransmitters

prevent a nerve signal from being passed on

Too few neurotransmitters also prevent the nerve signal from being passed on.







specialized cells

wrap tightly around axons

form the myelin sheath.

speed up the electrical signal (action potential)


special immune cells found only in the brain

detect damaged or unhealthy neurons

eat foreign invaders (bacteria and viruses)

displays chewed up parts on their cell surface to signal for help.


star-shaped glia

hold neurons in place

get nutrients to neurons

digest parts of dead neurons

astrocytes cannot generate action potentials

astrocytes communicate with neurons and modify the signals they send or receive

generate signals that are chemical

activated when the level of calcium ions increases inside the cell




fine-tune the action potentials


may be able to alter how a neuron is built

by directing where to make synapses or dendritic spines

can also attract new cells to their territory to repair any damage.

knowing more about these will also shed light on diseases


cause dramatic changes to synapses in the brain

they bypass the five senses

directly activates the brain's reward circuitry

cause a jolt of intense pleasure

Drugs of abuse

affect the brain in dramatic ways

the brain tries to adapt, but can’t

reduces the number of dopamine receptors at the synapse

after the user has "come down", they will need more of the drug the next time

As the brain continues to adapt to the presence of the drug, regions outside of the reward pathway are also affected. Brain regions responsible for judgment, learning and memory begin to physically change or become "hard-wired."

Once this happens, drug-seeking behavior becomes driven by habit, almost reflex. This is how a drug user becomes transformed into a drug addict.

Neurons outside of the reward pathway in meth-addicted brains have longer, thicker dendrites than those from a non-addicted brain.

Drugs can affect the brain and the body so dramatically that an overly large dose can actually kill the user. To learn more about how you can OD, follow the link below.

There are other factors aside from genetics and environment that can increase potential for addiction. Research has shown that the faster a drug can reach the brain, the more likely it is to be addicting. Different methods of delivery-smoking, injecting, or snorting- largely influence how quickly a drug finds the brain. Delivery methods become an important factor when ranking the addiction potential of a drug.

The fastest way to get a drug to the brain is by smoking it. When a drug like tobacco smoke is taken into the lungs, nicotine (the addictive chemical in tobacco) seeps into lung blood where it can quickly travel to the brain. This fast delivery is one reason smoking cigarettes is so addicting.

Injecting a drug directly into a blood vessel is the second fastest way to get a drug to the brain, followed by snorting or sniffing it through the nose. The slowest mode of delivery is by ingestion, such as drinking alcohol. The effects of alcohol take many minutes rather than a few seconds to cause behavioral and biological changes in the brain.

Crack cocaine (which is smoked) is much more addicting than powdered cocaine (which is snorted).

Nobody likes to wait, so users often choose a delivery method that gets them higher, faster. As addiction progresses, users often seek out the more immediate and more intense high. But this doesn’t seem to be the only reason that rapid delivery is an important factor in addiction. Recent evidence suggests that the mode of delivery can actually influence which part of the brain is most affected by a drug. Rapid delivery, such as smoking, affects brain regions that facilitate addiction.

Animal studies indicate that, when a drug is smoked, the brain regions affected most are those that control motivation, decision-making, and behavior in the frontal lobe. The human brain is shown here. These studies were actually done in rats and have not yet been replicated in the human brain.

Increased knowledge about drug delivery methods is providing new addiction therapies. It turns out that the slow delivery of a drug by ingestion or through the skin, produces a weaker longer-lasting effect. This temporarily stabilizes the brain and helps reduce the physical symptoms of withdrawal. And it's not addicting! So it's a safe and increasingly popular treatment option.

You can think of a brain pathway as a power line that connects two brain regions. Brain pathways are made up of interconnected neurons along which signals are transmitted from one brain region to another.

Dopamine is the neurotransmitter used by the reward pathway (also called the mesolimbic pathway, which is closely associated with the mesocortical pathway). But there are two other important pathways in the brain that utilize dopamine: the nigrostriatal pathway and the tuberoinfundibular pathway. Generally, drugs that affect dopamine levels in the brain affect all three of these dopamine pathways.

Dopamine and another neurotransmitter called Serotonin are released by a small number of neurons in the brain. But each of these neurons connects to thousands of other neurons. For this reason, dopamine and serotonin have a great deal of influence over complex brain processes.

Serotonin is another neurotransmitter that is affected by many of the drugs of abuse, including cocaine, amphetamines, LSD, and alcohol. Serotonin is produced by neurons in the Raphe nuclei. Raphe nuclei neurons extend processes to and dump serotonin onto almost the entire brain, as well as the spinal cord. Serotonin plays a role in many brain processes, including regulation of body temperature, sleep, mood, appetite and pain. Problems with the serotonin pathway can cause obsessive-compulsive disorder, anxiety disorders, and depression. Most of the drugs used to treat depression today work by increasing serotonin levels in the brain.

Glutamate and GABA (gamma-aminobutyric acid) are the brain's major "workhorse" neurotransmitters. Over half of all brain synapses release glutamate, and 30-40% of all brain synapses release GABA.
Since GABA is inhibitory and glutamate is excitatory, both neurotransmitters work together to control many processes, including the brain's overall level of excitation. Many of the drugs of abuse affect either glutamate or GABA or both to exert tranquilizing or stimulating effects on the brain.

Modern brain imaging techniques like PET and MRI (Magnetic Resonance Imaging) are becoming indispensible to researchers studying addiction and its effects on the brain. That is because addiction research requires looking inside the brain at areas where both drugs and natural chemicals act. Researchers can now determine how quickly drugs reach
receptors in the brain and how long they stay there. Or, view changes in brain activity after long-term drug use, during craving or withdrawal, or following various treatments
for drug abuse and addiction.

Before a PET scan begins a patient is given a safe dose of a radioactive compound. If the purpose of the PET scan is to study brain activity, doctors and scientists choose FDG (fluorodeoxyglucose), which is a modified glucose molecule.

Glucose is a type of sugar, and it is the main energy source for the brain. The injected or inhaled FDG will enter the person's bloodstream, where it can travel to the brain. If a particular area of the brain is more active, more glucose or energy will be needed there. The more glucose is used, the more radioactive material is absorbed.

FDG is a normal glucose molecule that has been attached artificially to a radioactive isotope of flourine. FDG can be absorbed by cells just like normal glucose.

The PET scanner measures energy that is emitted when positrons (positively charged particles) from the radioactive material collide with electrons (negatively charged particles) in the person's brain. The scan can take between 30 minutes to two hours to complete.

A computer then turns these measurements into multicolored two- or three-dimensional images. The result is a colorful picture showing which parts of the brain were most active, based on the amount of glucose being used there.

To measure the amount of radioactive material absorbed by the brain, a person lies on a moveable bed that slides into the tunnel-like opening of a device called a PET scanner.

To create the colorful PET image, a computer displays each measurement as a series of tiny dots. The color of each dot indicates the intensity of the energy that is recorded. Red indicates the highest intensity-in other words, the area of greatest brain activity.

A new technique called functional MRI can also be used to measure brain activity. MRI detects changes in blood flow rather than the quantity of a radioactive tracer.

When a particular site in the brain experiences increased activity, there is a sudden rush of blood flow to that area. This blood replenishes the oxygen used by the hard-working brain cells. By tracking variations in blood flow, functional MRI can detect active sites in the brain in real time.

An MRI machine looks a lot like a PET scanner but it has the added feature of an invisible magnetic field. This is useful because certain atoms (like hydrogen, a major component of water) give off a wave of energy when surrounded by giant magnets.

Since blood contains lots of water molecules and therefore lots of hydrogen atoms, the hydrogen atoms will produce pulses of energy when a person is immersed in a magnetic field. The energy emitted reflects increases in blood flow (and therefore brain activity) and can be detected by a computer.

MRI also differs from PET in that the energy pulse detected by the computer is in the form of radio waves rather than gamma rays. (A PET scanner detects gamma rays that are produced when positrons from the radioactive tracer collide with electrons in the brain.)

A form of energy called radiation travels through the atmosphere in waves that can be detected by a computer. The shorter the wavelength, the greater the energy. For example, gamma rays (detected by PET) contain much more energy than radio waves (detected by MRI). Frequent and prolonged exposure to high-level radiation such as ultra-violet waves and gamma rays is known to cause DNA damage. However, small, short doses of radiation (such as in PET scans) are generally considered relatively safe.

Drugs Of Abuse (what they are and what they do)
-Alcohol- Taken by drinking, depressant (a drug that temporarily produces a calming or drowsy effect) Causes loss of motor coordination, impairs reasoning, balance, speech, reaction time and judgement. When taken in large amounts, it can cause nausea and vomiting, lack of physical control, and possible death.

-Anabolic Steroids- Taken by injecting or by mouth. Man-made substances that are similar to males sex hormones. Sometimes prescribed to treat medical conditions related to low hormone levels. Because steroids promote muscle growth, they are sometimes abused by athletes and bodybuilders. Steroids may increase risk of heart attacks, strokes, and liver problems, as well as causing undesirable physical changes such as hair loss and acne. Steroids are not the addiction, but self image is.

-Cocaine- Take by snorting, injecting or smoking. It is a powerful stimulant, which is a class of drug that speeds up activity in the brain and nervous system. Cocaine causes increased energy, decreased appetite, and mental alertness in the user. Highly addictive. Also causes disturbances in heart rhythm, nausea, respiratory failure, strokes and seizures.

-Dissociative Drugs- Taken by mouth, snorting or smoking. PCP is often applied in either liquid or powder form to marijuana and tobacco cigarettes. Users feel disconnected from reality and out of control, often displaying unpredictable or violent behavior. High doses can result in convulsions, coma, high fever or death. Ketamine is similar to PCP, but less potent. Some users report a terrifying feeling, much like a near death experience. Dextromethorphan is a cough surpressant found in some nonprescription cold and cough medications. Taken at the recommended dose, it is safe. At much higher doses, it can present effects similar to PCP or ketamine.

-GHB & Rohypnol- Taken by mouth. GHB is a depressant that is abused by both party-goers for its relaxing effects and by bodybuilders for its ability to promote muscle growth. At high doses, it can quickly lead to seizures, loss of consciousness, coma or death. Rohypnol is benzodiazepine, a class of drug that is prescribed to treat anxiety disorders. Rohypnol is not approved for prescriptions use in the United States. When mixed with alcohol or other depressants, it can be deadly. Because GHB and Rohypnol are colorless, tasteless and odorless they can be slipped into someone’s drink without their knowledge. Because of this, they can be used as a “date-rape” drug.

-Hallucinogens- Taken by mouth, snorting and smoking. These are drugs that cause hallucinations. Physical effects of using LSD, mushrooms, or mescaline include dilated pupils, higher body temperature, increased heart rate and blood pressure, sweating, loss of appetite, sleeplessness, dry mouth, and tremors.

-Heroin- Taken by injecting, snorting or smoking. Most widely used opiate, which is a class of drug derived from the poppy plant. Although some opiates are prescribed to treat pain, heroin has no medical use. Heroin causes a rush of pleasure in the user that is usually followed by several hours of drowsiness. It may also cause nausea, vomiting, and severe itching. Heroin is extremely addictive. Symptoms of withdrawal after stopping heroin use include restlessness, muscle and bone pain, insomnia, diarrhea, vomiting, and cold flashes.

-Inhalants- Taken by sniffing fumes, spraying aerosols into the nose or mouth, huffing from an inhalant-soaked rag stuffed into the mouth. Inhalants are chemicals that can be inhaled to get an immediate high. Found in many household items such as aerosol sprays, cleaning fluids, paint, glue, paint thinner, gasoline, propane, nail polish remover, correction fluid, and marker pens. Since inhalants affect the brain with great force and speed, they can cause permanent brain damage or sudden death.

-Marijuana- Smoked as a cigarette, in a pipe, or in a hollowed out cigarette. Comes from a hemp plant. Most commonly used drug in America. Causes a peaceful or euphoric sensation. Soon the sensation passes and the user may feel sleepy or depressed. Impairs memory and attention span, effects coordination, balance and reaction time is slowed.

-MDMA- Taken by mouth. Acts as both a stimulant and a hallucinogenic. Can produce both energizing effects and distortions in perception and time. Most contain not only MDMA, but also other drugs such as methamphetamine, caffeine, or the diet drug ephedrine. Causes a variety of physical effects including chills, muscle clamping, involuntary teeth clenching, and significant reductions in mental abilities. Overdosing can cause panic attacks, loss of consciousness, and even seizures.

-Methamphetamine- Taken by mouth, snorting, injecting or smoking. Meth is a stimulant drug that, even in small amounts, has strong effects on the brain and nervous system. Causes mental alertness and increases energy, but has toxic effects on the brain. High doses can elevate body temperature to dangerous or lethal levels and may also cause convulsions. It is very addictive. Chronic users may also develop violent behavior, anxiety, insomnia, paranoia, delusions and psychological dependency on the drug.

-Nicotine- Taken by smoking, chewing, or dipping. Nicotine is the addictive substance in tobacco. It can act as a stimulant or sedative. It can be just as addictive as cocaine and heroin. Quitting can be complicated by intense cravings, irritability, and sleep disturbances. Tobacco is responsible for at least 30% of all cancer deaths, including nearly 90% of deaths from lung cancer. Also contributes to many other kinds of cancers including mouth, throat, esophagus, stomach, bladder and kidney.

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