Brain and Behavior Exam 2 Drug Actions and Substance Abuse In general all drugs of abuse cause dopamine release in the nucleus accumbens Stimulants o Amphetamines they increase dopamine release by reversing transporter in presynaptic terminal o Cocaine blocks the uptake of serotonin dopamine and norepinephrine serotonin release o Ecstasy increases dopamine release at high doses it also increases o Ritalin for ADHD and ADD o Behavioral effects include increased excitement activity alertness and mood It also lowers fatigue o Blocks the re uptake of dopamine at the synapse o Blocks the re uptake of dopamine and norepinephrine at the synapse o Differs from cocaine based on route of administration dose and Cocaine Ritalin release time Ecstasy o Reverses the serotonin transporter o Effects of long term use to neurons Large injections of ecstasy can destroy dopamine and serotonin neurons o Psychological effects Euphoria well being happiness stimulation increased energy extroversion feeling close to others increased empathy and sociability enhanced mood mild perceptual disturbances hallucinations and changed perception of colors and sounds o Hormones that it effects Oxytocin social attachment Vasopressin water retention antidiuretic Serotonin syndrome Nicotine o Too much serotonin is released into the body because of too much of a serotonin agonist or as a result of a mixing of drugs that all act in some capacity as serotonin agonists o Increases dopamine release in nucleus accumbens o Long term use causes dopamine cells to become less responsive than usual after repetitive nicotine use tolerance Other pleasures including nicotine itself become less reinforcing Opiates o Examples Morphine Fentanyl about 100x more potent than morphine Heroin Methadone o They bind to opioid receptors o We have opioid receptors because endorphins are endogenous morphines Morphine like hormones created in the body o Opiates increase dopamine levels in nucleus accumbens through the inhibition of GABA onto dopamine cells o Methadone it s similar to heroin and morphine mu opioid agonist We use it clinically to help prevent withdrawals and cut down Cannabinoids the person s drug cravings o How do they increase dopamine in nucleus accumbens It inhibits GABA in the VTA which results in more dopamine to the NA o Medicinal uses Inhibits serotonin type 3 synapses which produce nausea It helps cancer patients with nausea after chemotherapy o Psychological effects Intense sensory experiences Illusion of time passing slowly o Some withdrawal symptoms reported by heavy smokers include anxiety depression stomach pain craving loss of appetite and sleep problems Alcohol o Combines with GABA to produce longer normal effects of GABA It opens Cl channel wider than usual Results and anti anxiety and intoxicating effects due to this action o It s a glutamate receptor antagonist which is a depressant in this way Tolerance a decrease in the effectiveness of a drug that is administered repeatedly o Need more of a drug to get the same effect o Other pleasurable things become less reinforcing Why do people experience cravings to a drug even after withdrawal symptoms have subsided o Because the drug decreases stress o Because the person is reminded of it Sensitization an increase in the effectiveness of a drug that is administered repeatedly o Repeated cocaine use increases dopamine stimulation in the nucleus accumbens with each use So the more someone uses it the more dopamine is released to more dendrites How is the prefrontal cortex involved in decreased reinforcement from other pleasurable things o The prefrontal cortex usually stimulates the neural accumbens which facilitates its response to reinforcing experiences o Lots of drug use is inhibitory to the prefrontal cortex so it can t stimulate the NA to facilitate reinforcement Alcoholism continued use of alcohol despite medical or social harm even after having made a decision to quit or decrease drinking Type I Type II Later and gradual onset Fewer genetic relatives with alcoholism Equal quantity between men and women Less severe Earlier onset usually before 25 More rapid onset More genetic relatives with alcoholism Men outnumber women Often severe Often associated with criminality Genes involved in alcoholism Gene for a dopamine receptor Gene for the enzyme that breaks down dopamine Risk factors for becoming an alcoholic People who were described in childhood as impulsive risk taking easily bored sensation seeking and outgoing Sons of alcoholic fathers tend to have specific traits relating to how alcohol affects them and their neuroanatomy Antabuse antagonizes AD by binding to it so alcohol makes you sick Naloxone binds to and blocks opioid receptors It decreases the pleasure from alcohol Acamprosate helps with withdrawal so it s for people who have quit but need help getting through physical symptoms of withdrawal Major limiting factor to their efficiency They only work in people who are very motivated to quit drinking Medications used for alcoholism Development Plasticity and Brain Damage Early developmental structures of the nervous system o Neural plate thickened and flattened ectodermal tissue o Neural groove shallow median groove of the neural plate between the neural folds of an embryo o Neural tube formed when the neural groove deepens and creates a hallow tube o The space of the neural tube becomes the ventricular system and the tissue forming it will become the central nervous system The prefrontal cortex matures during late teens to early 20 s Six steps in brain development o Proliferation the production of new cells o Differentiation cells go from being nondescript to being future neurons final location o Migration the differentiated cells move from their birthplace to their o Myelination the process by which glia produce the fatty sheath that covers the axons of some neurons o Synaptogenesis formation of synapses o Pruning the loss of some neurons or synapses as a normal part of development usually by a process called apoptosis Sperry s newt experiment and what it taught us about the role of chemical gradients in axon guidance o Sperry cut the optic nerve of a newt and rotated the eye 180 degrees Even though the eye was turned backwards the retina and optic nerve reconnected and normal vision returned o This taught us that nerves know to regrow to the correct area due to a higher concentration of the original nerve s specific chemical identification tag Over what
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