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January 17th, 2013.docx

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NESC 3237
Sean Barrett

January 17th, 2013 January-17-13 2:33 PM Sensitization  The effects of a drug increase when administered repeatedly  Psychostimulants seem to be very prone to this effect  Self-administered drugs seem to often have this effect o Cocaine, amphetamine, nicotine, heroin and morphine  Cross-sensitization o So if you have drugs that work on the same neural systems o For example, stress acts on the neural circuitry involved in the reinforcing properties of many drugs  Can be conditioned to environments o Like when an animal is in a place where it is expecting the drug, the environment will prime that neural circuitry Sensitization: animals  The sensitization processes can be quite long lasting o Also in part quite context dependent o Suggesting some LTP occurring with structural changes over time  Your brain essentially learns how to respond to the drug with repeated administrations Sensitization: humans  Participants given a dose of amphetamine for the first time, and then given two additional doses over the next 4 days o Measured dopaminergic response to the amphetamine o Response when they gave the amphetamine two weeks later was much greater, and this response increase persisted when tested a year later  The magnitude of this sensitization is related to the extent of the person's novelty seeking personality traits o People that are more novelty seeking will see more sensitization in response to amphetamine Expectancy and context  You can have some sensitization or anticipatory expectancy effect when you're expecting to be receiving a drug o Effects the mesolimbic dopaminergic pathway  This pathway is the common pathway for many different drugs of abuse  Most of these drugs are known to increase the dopamine levels in the nucleus accumbens o So there is an "expectation pathway" in the brain  Be able to explain in essay form the contrast between the processes that occur when undergoing sensitization and tolerance **Start of Lecture 3** Drugs and the Brain  Drugs exert their effects on the brain by altering the brains neurochemistry  How they do it vary considerably  Some drugs will affect behaviour by facilitating release of neurotransmitter o Some by increasing the rate of this o Some by occupying the post-synaptic receptor spots, so NT can't o Some drugs interfere with reuptake processes o Some by increasing/decreasing the rate of the metabolism of the NT once it has been released  Can interfere with the brain's ability to produce certain neurotransmitters simply by changing a person's diet o If you give high protein diet, but lack tryptophan, you won't be able to produce serotonin temporarily Neurotransmitters  Acetylcholine o A cholinergic neurotransmitter  Biogenic amines o Catecholamines  Norepinephrine  Dopamine  Epinephrine o Indoleamine  Serotonin  Amino acid based o GABA  Very important for virtually every type of drug effect  The brains main inhibitory NT o Glutamate  Brains main stimulating neurotransmitter  Peptides Biogenic amines  Broken down by monoamine oxidase  MAO inhibitors are anti-depressants o One problem with using these is there are a lot of dietary restrictions associated with using these o Tobacco smoke contains MAO inhibitors  30-50% inhibition  The ones used for anti-depressants are 90% inhibitory  So when you quit smoking, the MAO inhibitory effects of the tobacco smoke last 3-6 months  May explain why quitting is so hard  Also broken down by COMT  Different drugs only act on certain subtypes of certain receptors o So the more universal to subtypes they are, the more receptors they will be able to cast an effect upon GABA  Inhibitory NT  Drugs like benzodiazepines enhance the ability of GABA to open the chloride ion channe
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