Chapter 11: Addiction
In this Chapter…
- Nicotine
- Alcohol
- Marijuana
- Opiates
- Psychostimulants
- Club Drugs
Introduction
- 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
- 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
Alcohol
- 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
Marijuana
- 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.)
Opiates
- 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
Psychostimulants
- 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
- 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