Chapter 11: Addiction

Drugs can alter the structure and chemical makeup of the brain * This produces a brain disorder called drug addiction * $drug addiction/dependence:$ characterized by a pathological desire for drugs * drug seeking and taking behaviors occupy too much time
A key reason for drug use is that abused drugs produce feelings of pleasure and/or remove feelings of stress & emotional pain
Drugs produce pleasure by activating the reward system * This reward system is normally involved in the type of learning that helps us stay alive * It evolved to mediate pleasurable & motivating effects of natural rewards * When the reward makes pleasurable feelings, we learn to repeat the actions that got us the reward in the first place
Drugs alter the ways neurotransmitters carry messages from neuron to neuron in different ways: * Some mimic the neurotransmitters * Some block the neurotransmitters * Others alter the way neurotransmitters are released/inactivated
Brain regions involved with executive functions and judgment are changed by drugs
Factors in drug addiction: * Motivation for drug use * People who take drugs to get high are more likely to be addicted than people who use them as painkillers * Genetic susceptibility and environmental factors (stress, etc.) * Characteristics of drugs themselves
$Tolerance$ : the progressive need for a higher drug dose to achieve the same effect * Varies person by person

Nicotine ats through the acetylcholine nicotinic receptor
Can act as a stimulant and depressant in the brain
Stimulates adrenal glands * Causes a “kick” * There’s a sudden release of glucose paired with an increase in blood pressure
Nicotine releases dopamine
Nicotine treatments relieve withdrawal symptoms, lower nicotine levels, totally eliminate one’s exposure to smoke * $Bupropion:$ originally an antidepressant but approved for use as a nicotine addiction treatment * this was the first non-nicotine treatment * $Varenicline:$ interacts with the acetylcholine nicotinic receptor and prevents nicotine from activating it * ends smoking

Genetic and environmental factors contribute to alcoholism
$Cirrhosis$ : scarring of the liver
$Ethanol$ : the active ingredient in alcoholic drinks
Alcohol acts as a stimulant in low doses & a depressant in high doses
Alcohol significantly alters behavior and mood * Too much alcohol causes heat loss and dehydration
Alcohol interacts with the GABA receptor * It calms anxiety, impairs muscle control, and delays reaction time
Higher doses of alcohol decrease the function of NMDA receptors * These receptors recognize neurotransmitter glutamate
Alcohol works by activating the endogenous opioid system * Susceptible individuals may feel an opioid-like euphoria from their own endorphins * $Naltrexone$ : works by blocking opioid receptors * developed for opioid addiction but can also be used for these individuals

Distorts perception and alters sense of time, space, and self * Marijuana can also produce intense anxiety
$Tetrahydrocannabinol (THC)$ : the active ingredient in marijuana * Binds to cannabinoid receptors * Many of these receptors are in neurons responsible for coordinating movement
The hippocampus contains many receptors for THC * This causes intoxicated people have poor short-term memory and problems processing complex information
Cannabinoid receptors usually bind to natural neurochemicals called endocannabinoids (anandamide, etc.)

Withdrawal symptoms of opiates * mild flu-like discomfort to severe muscle pain * stomach cramps * diarrhea * unpleasant mood
An increased amount of dopamine is released in the reward system → mimics the effects of endogenous opioids * Opiates reach the brain in 15 to 20 seconds * They bind to opiate receptors in brain regions involved in the reward system * They cause a brief rush of intense euphoria and then a couple of hours in a relaxed and contented state
Small doses of opioids can * relieve pain * depress breathing * cause nausea and vomiting * stop diarrhea
Large doses can make breathing shallow or even stop
$Methadone$ : A long-acting oral opioid that keeps craving, withdrawal, and relapse under control * Most common opioid addiction treatment * Prevents withdrawal symptoms that can motivate continued drug use
$Naloxone and Naltrexone$ : block opiate receptors so they don’t produce any pleasurable effects when taken
$Buprenorphine$ : causes a weaker effect on receptors than methadone, creating a limited high

Includes cocaine and amphetamines
Crack/cocaine can * enter the brain in seconds * produce a rush of euphoria * bring about a feeling of power or self-confidence
Psychostimulants are greatly able to elevate dopamine in specific brain regions * Activating the nucleus accumbens causes the progressively increasing motivation to take drugs * This leads to addiction
Cocaine users often go on binges * Crash occurs after use * This crash is characterized by emotional and physical exhaustion as well as depression
Symptoms come from a shutdown in dopamine & serotonin function and a greater response in brain systems that reach to stress
Vaccines to produce antibodies to cocaine are in clinical trials

Club Drugs include * ecstasy * herbal ecstasy * rohypnol (roofies) * GHB (gamma hydroxy-butyrate) * ketamine
Serious damage can occur from the use of some of these drugs
$MDMA$ - 3, 4-methylenedioxymethamphetamine (“adam”, “ecstasy”, “XTC”) * Synthetic psychoactive drug, hallucinogenic and amphetamine-like properties * Problems are similar to those associated with the use of amphetamines & cocaine
Chronic ecstasy use causes long-term changes in brain areas of thought, memory, and pleasure
Rohypnol, GHB, and Ketamine are all CNS depressants * They are colorless, tasteless, odorless * They can be used by some in beverages and unknowingly ingested
Rohypnol can be lethal when mixed with alcohol and other depressants
$GHB (Gamma hydroxy-butyrate)$ : a drug that has been abused for euphoric, sedative, and body-building effects
$Ketamine$ : a Central Nervous System depressant, hypnotic, and analgesic with hallucinogenic properties * Also used as a general anesthetic

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