reward and addiction (4.2)

Question 1

motivation

Answer 1

a theoretical construct; used to explain why people do what they do

Question 2

what we are motivated toward (2)

Answer 2

survival, reward

Question 3

what influences motivation (3)

Answer 3

memory, executive functions, emotional state

Question 4

reward

Answer 4

the positive/pleasurable consequence of an action; a potent motivator; typically serve as reinforcements (increase probability of behavior when presented)

Question 5

primary (natural) vs secondary rewards

Answer 5

primary: necessary for the survival of the species (i.e. sleep, thirst, food, temperature, sexual reproduction)
secondary: objects that derive their value from primary rewards (i.e. money -> food)

Question 6

mesotelencephalic dopamine system

Answer 6

plays an important role in intracranial self-stimulation; neurons project from mesencephalon (midbrain) to telencephalon

Question 7

midbrain areas in the mesotelencephalic dopamine system (2)

Answer 7

substantia nigra, ventral tegmentum

Question 8

nigrostriatal vs mesocorticolimbic pathway

Answer 8

nigrostriatal: substantia nigra neurons project to the dorsal striatum
mesocorticolimbic pathway: VTA neurons project to cortical and limbic sites, including the nucleus accumbens; the major “reward” pathway for ICSS and natural rewards; anticipatory pleasure

Question 9

nucleus accumbens

Answer 9

receives direct dopaminergic input from the VTA; indirectly excites the prefrontal cortex via the ventral palladium (part of basal ganglia) and DM nucleus (part of thalamus); lesions eliminate self-administration of addictive drugs

Question 10

drug addicts

Answer 10

those who continue to use a drug despite its adverse effects on their health and social life

Question 11

drug administration (4)

Answer 11

ingestion: easy, but unpredictable
injection: fast and predictable, but need needle and potential for scar tissue, infection and overdose
inhalation: fast, but hard to regulate and may damage lung tissue
absorption: easy, but damage to nasal, oral and rectal mucosa

Question 12

mechanisms of action for drugs

Answer 12

once a drug enters the bloodstream, it must pass through the BBB to have its effects; drugs influence the NS by altering the way nerve cells send, receive and process information

Question 13

liver

Answer 13

where the actions of most drugs are terminated [by enzymes]

Question 14

drug tolerance

Answer 14

decreased sensitivity to a drug as a result of exposure to it; (1) a given dose has less effect or (2) a larger dose is needed to produce the same effect; metabolic (less drug gets to site of action) or functional (reduced sensitivity; fewer receptors or less responsive at sites of action)

Question 15

withdrawal syndrome

Answer 15

an adverse physiological reaction triggered by a sudden elimination of a drug after significant amounts of it have been in the body for a period of time

Question 16

tobacco (ingredient, health, effect)

Answer 16

ingredient: nicotine
health: smoker’s syndrome (chest pain, labored breathing, wheezing, coughing), cancer
effect: nicotine binds to acetylcholine receptors on dopaminergic neurons in the VTA; sodium influx and increased release of dopamine in NAc

Question 17

alcohol (ingredient, health, effect)

Answer 17

ingredient: ethanol
health: alcohol withdrawal syndrome (vomiting, convulsions, delirium tremens), Korsakoff’s syndrome, cirrhosis
effect: ethanol reduces activity of voltage-dependent potassium channels in VTA neurons; relative refractory period of VTA dopaminergic neurons is reduced (fire more often); increased release of dopamine in NAc

Question 18

marijuana (ingredient, health, effect)

Answer 18

ingredient: THC, cannabis sativa
health: short-term memory impairment (DLPFC), interference with tasks involving multiple steps, respiratory problems
effect: THC binds to CB1 receptors on GABAergic inputs in the VTA, reducing calcium influx and thus transmitter release; VTA dopaminergic neurons fire more often; increased release of dopamine in NAc

Question 19

amphetamines (ingredient, health, effect)

Answer 19

ingredient: levo- and dextro-amphetamine
health: short-term working memory impairment; altered cognitive (executive) control
effect: competes with dopamine for reuptake in the NAc; causes reuptake transporters in the terminal button to reverse their mode of operation; increased dopamine in the NAc

Question 20

cocaine (ingredient, health, effect)

Answer 20

ingredient: cocaine, anesthetic
health: cocaine psychosis from binges or sprees (unconsciousness, seizures, heart attack, stroke)
effect: acts as a serotonin-norepinephrine-dopamine reuptake inhibitor (triple reuptake inhibitor (TRI)); prevents dopamine reuptake and thus increases levels in the NAc

Question 21

opiates (ingredient, health, effect)

Answer 21

ingredient: morphine, codeine, heroin
health: relatively minor health hazards (indirect related to needle use)
effect: bind to endogenous opiate receptors on VTA GABAergic neurons, enhancing potassium efflux and thus reducing transmitter release; VTA dopamine neurons are disinhibited; increased release of dopamine in the NAc