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