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

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