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Lecture 7

Human Brain and Behaviour: lecture 7 and 8

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University of Toronto Scarborough
Ted Petit

PSYB65 – Human Brain and Behaviour: Lectures 7 and 8  4 Classifications of drugs - Prescription drugs - Over-the-counter drugs - Social drugs - Non-commercial drugs (or available commercially but not for psychoactive effects)  Tolerance: drug taken repeatedly  reduced behavioural effect - Brain responds to compensate for repeated action of drug by changing sensitivity or number of receptors for drug  Withdrawal: someone who stops taking a drug after having been on it long enough to build tolerance to it and have had physiology/psychological changes – the behavioural effects of withdrawal are exactly the opposite of the behavioural effects of the drug itself - At normal level of activation, stimulant becomes less activated - At normal level of activating, depressant becomes hyperactivated - Coming off of a stimulant is not fatal, but off a depressant may cause seizures and may be fatal - There is also the psychological effect of “craving” with withdrawal  Addiction 1. Psychological addiction: behavioural dependence on drug – difficult to define/measure - Doesn’t have to be a drug 2. Physical addiction: physiologically measurable symptoms - Addictive qualities of the drug depend more on the form of the drug + mechanism of administration than on the drug itself: typically has to do with speed + dosage (eg. Cocaine leaves in tea  not very addictive vs. powder  more addictive vs. injecting it  extremely addictive)  Stimulants: cause the EEG to move into a more activated state - Caffeine o Inhibits sleep o Some tolerance develops o Stops headaches o Stimulates digestive system o Withdrawal symptoms: (opposite of drug’s symptoms) headaches, constipation o Not very toxic; estimated overdose = 70-100 cups of coffee needed to kill you o Inhibits breakdown of cAMP  increased amounts of cAMP  increased glucose production and heightened cellular activity - Nicotine o Mimics acetylcholine at nicotinic receptors o Causes adrenaline release  increases heart rate + blood pressure o Some tolerance but not extreme o Withdrawal: opposite of stimulation: period of depression o Toxicity: not very toxic except in infants - Cocaine o Comes from cocoa leaves (contain about 2% cocaine) o Stimulant-increases heart rate + respiration o Toxicity varies by administration – if administered quickly at a very high dose (esp. intravenous) and works directly on heart muscles to stop heart from beating o Primary mechanism of action: prevents reuptake of norepinephrine  stimulates post- synaptic neuron for a longer time  increased activity in noradrenergic cells o Some tolerance develops but not extreme o Withdrawal: period of depression o Addiction is directly related to type of cocaine: injecting is reasonably addicting, powder less addictive, from leaves in tea is not very addictive - Amphetamine o Discovered in 1932 so relatively recent o Reduction in fatigue and “fatigue-associated decrement in performance” o Increases activity in the medial forebrain bundle (MFB) – reward system, the part of the brain that makes us feel good (in forebrain and hypothalamus) o 2 primary uses: (1) a derivative is used in kids with ADHD, Ritalin (methylphenidate) is most effective, to help focus and (2) to suppress appetite for weight control o Tolerance to appetite-suppressing effect built up in 2-4 weeks  o Tolerance depends on behavioural effect: on appetite suppression = 2-4 weeks (was banned in Canada in 1973 from being prescribed for weight loss), on mood elevation takes much longer, ADHD kids can take it for years without showing tolerance o Most common types: D-amphetamine, L-amphetamine and methamphetamine o 4 mechanisms of action: (1) causes norepinephrine to leak from presynaptic terminal without action potential, (2) causes increase in norepinephrine release when there is an action potential, (3) blocks reuptake of norepinephrine, (4) direct mimicker on receptor site o Withdrawal: depression, fatigue, increase in appetite o High doses over long periods of time  compulsive behaviour, “coke bugs” (feeling that there are bugs running around under your skin, some people try to remove them with nails or knife!), paranoid psychosis, auditory + visual hallucinations, clear setting of consciousness, become suspicious, hostile, aggressive, violent  Depressants: cause EEG to shift to a more relaxed/ drowsy state - GABA is primary inhibitory neurotransmitter in the brain 2. Barbiturates - Bind to GABA receptors and activate them (activates inhibitor)  slows down activation in the brain - Synergistic with most other depressants (can be fatal) - Used as
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