neurochemistry and drug addiction

Question 1

What types of substances can get through the blood-brain barrier?

Answer 1

By passive diffusion:
Water, Alcohol, Nicotine, and O2, CO2, N2O

By active transport:
Glucose and Amino acids

Small, highly fat-soluble molecules can get in if not chucked out by extrusion mechanisms

Most large molecules, bacteria, etc., are blocked

Question 2

resting potential

Answer 2

the electrical potential of a neuron or other excitable cell relative to its surroundings when not stimulated or involved in passage of an impulse

caused by the shifting of positively charged sodium ions from the outside to the inside of the cell, results in the transmission of nerve impulses

Question 3

depolarisation

Answer 3

Neurons can undergo depolarization in response to a number of stimuli such as heat, chemical, light, electrical or physical stimulus.

During the depolarization phase, the gated sodium ion channels on the neuron’s membrane suddenly open and allow sodium ions (Na+) present outside the membrane to rush into the cell.

Question 4

hyperpolarisation

Answer 4

is a change in membrane potential. Measured using patch clamping that allows them to record ion currents passing through individual channels

Question 5

serotonin

Answer 5

mood and temperature regulation, aggression, and sleep cycles

Question 6

dopamine

Answer 6

motor function and reward

Question 7

acetylocholine

Answer 7

muscle contraction (PNS), corticol arousal (CNS)

Question 8

glutamate

Answer 8

main excitatory neurotransmitter; participates in relay of sensory info and learning

Question 9

GABA

Answer 9

main inhibitory neurotransmitter

Question 10

anandamide

Answer 10

pain release, increase in appetite

Question 11

norepinephrine

Answer 11

brain arousal and other functions like mood, hunger, and sleep

Question 12

Which neurotransmitter’s site does nicotine occupy? How does nicotine use produce psychological reward?

Answer 12

nicotine binds predominantly to (nACh) receptors in the CNS; the primary is the α4B2 nictonic receptor in the VTA, it results in a release of dopamine in the nucleus accumbuns (nAcc) which is linked to reward

Question 13

What are the main effects of alcohol on neurons in the brain?

Answer 13

Small molecules: Soluble in both water and fat – gets into everywhere
Depresses neural firing in moderate to high doses
Stimulates neural firing (and social interaction) in low doses: Disinhibition

Question 14

Which type of neurotransmitter’s receptors does cannabis target?

Answer 14

CB1 receptor – common g-protein linked receptors in the brain
CB2 receptor – CNS and immune system
Endocannabinoids – neurotransmitters (e.g., anandamide)

Question 15

Which neurotransmitter’s action is affected by cocaine? How?

Answer 15

Blocks dopamine transporters (responsible for reuptake)

Question 16

what neurotransmitters are involved in euphoria

Answer 16

Endorphins: These neurotransmitters than inhibit the transmission of pain signals and promote feelings of euphoria.

Question 17

Opiates can also offer analgesic effects? What do they do to cells in the pain pathways to reduce pain transmission?

Answer 17

?

Question 18

If a drug is ingested, what’s the most likely place of absorption?

Answer 18

• Easy and relatively safe
• Mostly intestinal absorption
• Absorption via digestive tract unpredictable

Question 19

if a drug is inhaled?

Answer 19

• Absorbed through capillaries in lungs

Question 20

Why is intravenous injection of a psychoactive drug highly effective?

Answer 20

into veins, drug delivered directly to brain

Question 21

drug tolerance

Answer 21

is a shift in the dose-response curve

1) in tolerant individuals, the same dose has less effect
2) in tolerant individuals, a greater dose is required to produce the same effect

Question 22

effect selectivity

Answer 22

tolerance forms to some but not all effects of drug

Question 23

cross-tolerance

Answer 23

may extend to other drugs that work by similar means

Question 24

functional tolerance

Answer 24

(The sites of action become less responsive to drug)
• Number of receptors reduces
• Doesn’t bind to receptors as well
• The cell isn’t as affected

Question 25

metabolic tolerance

Answer 25

Less of the drug gets to sites of action

Question 26

why do withdrawal symptoms tend to be the opposite of the initial effects of the drug

Answer 26

When a drug user experiences withdrawal symptoms in the absence of the drug, he/she can be considered physically dependent on the drug. This simply means that this person’s nervous system has adapted to the presence of this drug, and now requires its presence for normal functioning. Sudden absence of the drug disrupts this new balance, and causes the opposite symptoms.

Question 27

contingent tolerance

Answer 27

differential tolerance to the anticonvulsant, hypothermic, and ataxic effects of ethanol.

Question 28

hypothermic effects of alcohol

Answer 28

Decreased perception and sensation of cold. …
A heavily drinking person exposed to cold who has been not eaten for a day or more may develop hypoglycemia, which may result in decreased shivering and therefore decreased heat

Question 29

How is addiction different from drug dependence?

Answer 29

drug addiction being more of a psychological issue and dependence being more physiological.

• Addicts continue to use a drug despite its adverse effects on health and social life
• Addiction and physical dependence may occur together or separately
• After withdrawal symptoms due to physical dependence have subsided, addicts may still crave the drug

Question 30

What are the problems with physical dependence theories of addiction?

Answer 30

Can’t explain:
• Addicts relapse long after detoxification
• Individuals begin using drugs
• Addictions develop to drugs that do not produce severe withdrawal symptoms

Question 31

incentive-sensitisation theory

Answer 31

it is the dopamine released by the brain that creates the emotional and physical need to continue following an addiction. Even something as simple as a favourite food can be enough to form a trigger that develops a cue that cannot be ignored.