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PSYB65 - Lec 7 (near verbatim).doc

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University of Toronto Scarborough
Ted Petit

PSYB65: Lec 7 -alcoholics take up most beds in psychiatric wards; addiction of drugs = important -classification of drugs: -prescription drugs (what’s a prescription drug in one country may not be another country codeine in Canada doesn’t need to be prescribed, in US = must be prescribed) -over-the-counter = legal w/out prescription -social drugs = don’t have to get from pharmacy (alcohol, nicotine, caffeine) -not produced commercially (ex: marijuana, cocaine, LSD) or if they are produced commercially, it isn’t for their psychoactive effect (airplane glue) -tolerance: w/ most drugs, as you take them repeatedly, you get reduced behavioural effect w/ repeated use of a drug -how does this work? -when you repeatedly take drug, brain somehow compensates for the repeated intake of the drug by somehow changing either sensitivity or the # of receptors that are affected -ex) whenever you normally have activation, nt is released and stimulates receptor sites on post-synaptic neuron; person is on stimulant (cocaine, amphetamine) = have over-activation of the synapse  plasticity occurs, brain adapts; over- stimulation of post-synaptic cells so the brain compensates by either reducing the sensitivity or # of the post-synaptic receptors -tones itself down, comes back to normal levels of functioning even though pre- synaptic cell fires at high rate due to psychostimulant -person takes depressant (barbiturate/Valium): since taking this slows down the pre- synaptic neuron, not releasing as much nt; post-synaptic cell will respond by increasing the sensitivity or the number of receptors it has  even though lower amount of nt being released, it will activate more receptors  increases level of activation of post-synaptic neuron back up to normal level -it’s what goes on post-synaptically that really counts!! -withdrawal: behavioural effects in patient after stop taking drug after having built tolerance for the drug -physiological or behavioural output changes -what causes withdrawal symptoms? -after brain compensates for having taken stimulant drug for a long time (tolerance) and then you take the drug away but the post-synaptic cell still has the reduced levels of receptors; at normal levels, with no drug, lower levels of the receptor isn’t enough to activate the post-synaptic neuron -the effect is opposite of the drug itself -if you have a stimulant and you come off of it, brain = depressed b/c has already damped itself down due to tolerance and when you take away the drug, you come back to normal levels of activation BUT there aren’t enough receptors to activate it -if taking depressant like barbiturate, not enough activation of the post-synaptic cell while taking the drug, so brain increases the # of receptors on the post-synaptic cell; now, take person off the depressant, now going thru w/drawal  the post-synaptic neuron is no longer being depressed by the drug, goes back to normal levels of activation (ex: coffee has worn off)  all of the extra receptors and normal level of activity will drive the post-synaptic cell like crazy b/c of the extra receptors  whenever you come off depressants, you hyper-activate the post-synaptic neuron -normal baseline levels and then given stimulant; take patient off stimulant, they don’t just come back down to baseline levels, they get understimulated period which looks like a depression and then come back to normal -if person has been on alcohol (depressant) for long periods of time, take them off alcohol  they don’t just come back to normal, since they have too many receptors, become super-activated (nervous system becomes over-activated b4 coming back to normal) -when someone is addicted to a stimulant and they come into a psychiatric ward and you take them off the stimulant  will be like their brain is less activated  looks like depression  will be tired, sleepy, lethargic, disorientation, may be a bit depressed -under normal circumstances w/ normal human beings, this is NOT life-threatening -when someone is on a depressant for a long time (alcoholics) and is addicted to it; they are taken off the depressant, their nervous system = hyper-excited  you get seizures when you have hyper-active aggregate of neurons -never take alcoholic off alcohol w/out replacing it w/ something else, generally Valium or Valium-derivative is used -taking person off depressants can lead to seizures and is life-threatening -replace w/ another depressant, wean the person off Valium **the behavioural effect of w/drawal is the opposite effect of the drug itself** -during w/drawal, the person has the psychological effect of craving the drug (almost always) -if there are no w/drawal symptoms, would say that the drug isn’t addictive -addiction: there are diff types of addiction, difficult term to define: psychological addiction and physical addiction -psychological addiction: behavioural dependence on the drug; hard to define, more impossible to measure, doesn’t even have to be a drug -physical addiction: on w/drawal, there are some physiologically measurable symptoms (ex: changes in pupil dilation, sweating, bp changes etc;) something you can measure objectively -addictive qualities of a drug depends on form of drug/mechanism of administration more than the drug itself; usually has to do w/ speed/dosage that form of the drug works (ex: cocaine, leaf of coca tree has 2% cocaine in it  put it in water to drink as stimulant  legal in south America  not particularly addictive; in U.S.  concentrate the cocaine = white cocaine = sort of addicting; inject free-base = instant = even more addicting = more concentrated = same drug, administered in a rapid form is much more addicting than same drug that takes long
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