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Lecture 6


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Suzanne Erb

PSYC62: LECTURE 6 – PSYCHOSTIMULANTS The Psychostimulants  Read about minor stimulants in textbook***  Widespread effect on CNS  Stimulant drugs have effects on other systems, but monoamine mostly underlying motivational and emotional responses o Profound effects on cognition, mental function and emotion  Potent  Can be taken orally, snorted, injected and smoked  Effects vary depending on mode of administration  Rapid absorption = greater intense peak liability than a mode of slower absorption into circulation  Cocaine metabolized quickly and effects deteriorate within minutes of administration Slide 4  Produces hyperactivity in animal models  Mid brain dopamine system is critical for expression of psychostimulant motoric effects  Convenient behavioural measure for neural adaptations that occur in dopamine system as a consequence of repeated exposure to these drugs  Effects of at lower doses may not persist in higher doses  Inverted U at higher doses o Stereotypic effects that counter motor effects at lower doses Psychostimulant Dependence  Depression, anxiety and craving studied most  Depression in humans  Anxiety in animals  Wanting of more drug may reflect desire to overcome negative affect (anxiety and depression)  Desire to achieve intense euphoria as well o Short term withdrawal – negative reinforcement and positive reinforcement are in play  Negative – reduction of negative affect associated with desire to take drugs  Positive – actual pull of drug itself is motivating behavior  Long term abstinence period after withdrawal period may lead to a desire to produce euphoria Phases of withdrawal  Not all individuals advance to all stages of withdrawal  Crash o Lasts several days after termination of drug use o Involves exhaustion alternating with depression and anxiety o Sleep for long periods of time o Show no desire to take drug again at this point in time o Binge pattern o Stop taking drug altogether for a period of days and then restart taking drugs again  Withdrawal o Lasts several weeks o Experience intense cravings for more drug o Moderate to severe depression o Inability to experience pleasure – anhedonic state o Individual will not be successful in maintaining abstinence  Extinction o Lasts for indefinite period of time o Weeks, months, years o Continue to experience intermittent cravings, but don’t take the drug o If individual experiences cues enough and doesn’t give into cravings, then the link should weaken and no longer lead to craving Dextroamphetamine – active isomer of amphetamine  Taken orally or injected  Medically approved usages o Obesity, narcolepsy (individuals lose consciousness), ADHD o Treatment-resistant depression  Drug used recreationally Ritalin  Treats ADHD  Discovered by Charles Bradly in 1937  Dose can calm hyperactive children  Paradox – using a stimulant to treat highly frequent, hyperactive behavior  Reflects some performance of noradrenaline, dopamine systems  Boosts activity in a hypoactive system Methamphetamine  Most potent and highly abused amphetamine Methcathinone  Newest Schedule  Methcathinone does not have medically approved usages Amphetamines  When used recreationally, referred to as meth or speed  Can be dissolved in water and swallowed  Glass-like crystals can be smoked/snorted or dissolved in water and swallowed  Prevalence of amphetamines not as high as other drugs, but still high Pharmacology  Drugs that stimulate monoamine synapses  Produce activity in monoamine systems  Meth results in increase in dopamine at synapse where available for post-synaptic binding  Act like cocaine  Transporter molecules embedded in membrane of presynaptic terminal, transmitter released from it will bind to terminal and taken up again to have subsequent effects?  Blocks reuptake of dopamine  Amphetamine prevents dopamine from being recycled so we could get a greater effect at synapse  Reverse transport effects o Cause more release of dopamine o Cocaine does not engage in this, only amphetamine  Inhibit monoamine oxidase o Monoamine oxidase metabolizes monoamines in presynaptic terminal o Amphetamine inhibits this o Results in increase in concentration of monoamines – dopamine Synapses in nucleus accumbens are responsible for rewarding effects Historical Perspective th  Amphetamine use increased as cocaine use decreased in 18 century  Am
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