[Paleopsych] NS: A concise guide to mind-altering drugs

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A concise guide to mind-altering drugs
http://www.newscientist.com/article.ns?id=mg18424735.900&print=true
      * 13 November 2004

Alcohol

    What is it?

    Ethanol produced by the action of yeast on sugars.

    What does it do?

    Ethanol is a biphasic drug: low doses have a different effect to high
    doses. Small amounts of alcohol (one or two drinks) act as a
    stimulant, reducing inhibition and producing feelings of mild
    euphoria. Higher doses depress the central nervous system, initially
    producing relaxation but then leading to drunkenness - characterised
    by poor coordination, memory loss, cognitive impairment and blurred
    vision. Very high doses cause vomiting, coma and death through
    respiratory failure. The fatal dose varies but is somewhere around 500
    milligrams of ethanol per 100 millilitres of blood.

    How does it work?

    At low doses (5 milligrams per 100 millilitres of blood), alcohol
    sensitises NMDA receptors in the brain, making them more responsive to
    the excitatory neurotransmitter glutamate, so boosting brain activity.
    These effects are most pronounced in areas associated with thinking,
    memory and pleasure. At higher doses it desensitises the same
    receptors and also activates the inhibitory GABA system.

Amphetamine-type stimulants

    What are they?

    A class of synthetic drugs invented (and still used as) appetite
    suppressors. Includes amphetamine itself and derivatives including
    methamphetamine and dextroamphetamine.

    What do they do?

    Amphetamines are powerful stimulants of the central nervous system,
    producing feelings of euphoria, alertness, mental clarity and
    increased energy lasting for 2 to 12 hours depending on the dose. The
    downsides are increased heart rate and blood pressure, nausea,
    irritability and jitteriness, plus fatigue once the effects have worn
    off. Overdosing can lead to convulsions, heart failure, coma and
    death. The fatal dose varies from person to person, with some reports
    of acute reactions to as little as 2 milligrams and others of
    non-fatal 500-milligram doses. Most deaths from overdose have been
    among injecting users.

    How do they work?

    Their principal effect is to block dopamine transporters, which leads
    to higher-than-normal levels of the pleasure chemical dopamine in the
    brain.

Caffeine

    What is it?

    An alkaloid found in coffee, cocoa beans, tea, kola nuts and guarana.
    Also added to many fizzy drinks, energy drinks, pep pills and cold and
    flu remedies.

    What does it do?

    A stimulant of the central nervous system. Pure caffeine is a
    moderately powerful drug and is sometimes passed off as amphetamine.
    In small doses, such as the 150 milligrams in a typical cup of filter
    coffee, it increases alertness and promotes wakefulness. Caffeine also
    raises heart and respiration rate and promotes urine production.
    Higher doses induce jitteriness and anxiety. The fatal dose is about
    10 grams.

    How does it work?

    Caffeine blocks receptors for the neurotransmitter adenosine, which is
    generally inhibitory and associated with the onset of sleep. Also
    raises dopamine levels, and stimulates the release of the
    fight-or-flight hormone adrenalin.

Cannabis

    What is it?

    Leaves, buds, flowers and resin from the cannabis plant, Cannabis
    sativa, a native of central Asia. The plant contains numerous
    psychoactive compounds called cannabinoids, the most potent of which
    is delta-9-tetrahydrocannabinol (THC). Cannabis is usually smoked in
    the form of dried leaves and buds, or as a dried resin (hashish).

    What does it do?

    Smoked in moderate quantities, cannabis can produces feelings of fuzzy
    mellowness and general well-being. It can interfere with memory and
    increase appetite ("the munchies"). Some users experience nausea,
    anxiety and paranoia. If eaten, the resin can be powerfully
    hallucinogenic. No fatal dose has ever been recorded in humans

    How does it work?

    THC latches onto specific receptors in the brain that are known to be
    involved in reward, appetite regulation and pain perception, though
    their precise role has yet to be worked out.

Cocaine

    What is it?

    An alkaloid extracted from the leaves of the coca plant (Erythroxylon
    coca), a native of the eastern slopes of the Andes. It is commonly
    consumed in the form of the hydrochloride salt, a white crystalline
    powder which is usually snorted into the nostrils. Crack cocaine is
    pure cocaine liberated from the hydrochloride (hence known as "free
    base"), which makes it smokeable.

    What does it do?

    Cocaine is a potent stimulator of the central nervous system; a
    typical dose (about 50 to 100 milligrams) rapidly induces feelings of
    self-confidence, exhilaration and energy which last for 15 to 45
    minutes before giving way to fatigue and melancholy. Crack cocaine
    condenses these effects into a shorter and more intense high. The drug
    also increases heart rate and blood pressure, sometimes fatally. Very
    high doses depress brain stem function, potentially leading to cardiac
    arrest and respiratory failure. The fatal dose can be as low as 1
    gram.

    How does it work?

    Its principal effect is to block the re-uptake of dopamine, serotonin
    and noradrenalin into neurons, leading to higher-than-normal levels of
    these neurotransmitters in the brain.

Dissociatives

    What are they?

    A class of hallucinogenic drugs that produce feelings of
    depersonalisation and detachment from reality. The most commonly used
    are ketamine and its relatives DXM (dextromethorphan hydrobromide) and
    PCP (phencyclidine, angel dust).

    What do they do?

    In small doses (up to about 75 milligrams) ketamine produces a
    psychedelic stimulant effect. The effect of higher doses has been
    described as an "out-of-body" experience. Users lose all sense of self
    and feel a detachment of mind and body, leading to a trance-like state
    in which they can experience a "superior reality" full of dazzling
    insights and visions. Some people find it wonderful, others
    terrifying. Effects last about an hour and wear off rapidly, leaving
    the user feeling groggy, and sometimes traumatised. Accidental
    overdoses are unknown: the drug has a wide safety margin.

    How do they work?

    Ketamine is an inhibitor of NMDA receptors, which normally respond to
    the excitatory neurotransmitter glutamate. This has the effect of
    severely depressing activity in many parts of the brain while leaving
    some functions intact.

Ecstasy

    What is it?

    The amphetamine derivative MDMA
    (3,4-methylenedioxy-N-methylamphetamine). What is sold as ecstasy on
    the street, however, often contains no MDMA.

    What does it do?

    Technically known as a hallucinogenic amphetamine and also as an
    "empathogen", MDMA produces feelings of energy, euphoria, empathy,
    openness and a desire for physical contact (users are often described
    as "loved up"), plus mild visual and auditory hallucinations. Effects
    last for several hours and are followed by an equally lengthy period
    of lethargy and mild depression. MDMA is not toxic per se but can
    cause death due to overheating and dehydration. It also inhibits the
    production of urine and so can lead to a fatal build-up of fluid in
    the tissues.

    How does it work?

    The drug causes the brain to dump large amounts of the mood-modulating
    neurotransmitter serotonin into the synapses, and also raises dopamine
    levels.

Hallucinogens/psychedelics

    What are they?

    A broad class of natural and synthetic compounds that profoundly alter
    perception and consciousness. The most widely used are the LSD group,
    including LSD (lysergic acid diethylamide), LSA (d-lysergic acid
    amide), DMT (dimethyltryptamine, found in ayahuasca) and psilocybin
    (the main active ingredient of magic mushrooms).

    What do they do?

    LSD produces experiences far removed from normal reality, including
    visual and auditory hallucinations, synaesthesia, time distortion,
    altered sense of self and feelings of detachment. Surfaces undulate
    and shimmer, colours are more intense and everyday objects can take on
    a surreal and fascinating appearance. The experience can be extremely
    frightening. After effects include fatigue and a vague sense of
    detachment.

    LSD is one of the most potent psychoactive substances known. Only 25
    micrograms are required to produce an effect; 100 micrograms will
    induce 12 hours or more of profound psychedelia.

    How do they work?

    No one really knows. LSD stimulates three subtypes of serotonin
    receptor, 5-HT2A, 5-HT2C and 5-HT1A, though it is not clear that this
    alone can account for its effects.

Opiates

    What are they?

    Any compound that stimulates opioid receptors found in the brain,
    spinal cord and gut. The word "opioid" derives from opium, the
    narcotic resin extracted from unripe seed pods of the opium poppy
    (Papaver somniferum). The opiates include naturally occurring
    alkaloids such as morphine (the main active ingredient of opium),
    derivatives of these such as heroin, and entirely synthetic compounds
    such as methadone.

    What do they do?

    Heroin, the most commonly used opiate, can induce euphoria, dreamy
    drowsiness and a general sense of well-being. The effects of injecting
    the drug have been described as a "whole-body orgasm", though some
    users experience no pleasurable effects at all. It also causes nausea,
    constipation, sweating, itchiness, depressed breathing and heart rate.
    Higher doses lead to respiratory failure and death. The fatal dose
    depends on tolerance and how the drug is taken but a naive user would
    probably die after injecting 200 milligrams.

    How do they work?

    By activating any of the three subtypes of opioid receptors. These
    normally respond to the body's natural painkilling chemicals including
    endorphins, which are released in highly stressful situations where
    pain would be disadvantageous.

Tobacco

    What is it?

    Dried leaves of the tobacco plant Nicotiana tabacum, a native of South
    America. Usually smoked but can also be snorted as snuff or chewed.
    The main active ingredient is the alkaloid nicotine.

    What does it do?

    Nicotine is a mild stimulant which increases alertness, energy levels
    and memory function. Paradoxically, users also report a relaxant
    effect. It also increases blood pressure and respiration rate and
    suppresses appetite. Larger doses cause hallucinations, nausea,
    vomiting and death. The lethal dose is about 60 milligrams; a typical
    cigarette delivers about 2 milligrams of nicotine into the
    bloodstream.

    How does it work?

    Nicotine's principal effect is to stimulate nicotinic acetylcholine
    receptors in the brain, which leads to increased levels of the
    fight-or-flight hormone adrenalin. Also increases levels of dopamine.