neurochemistry and drug addiction Flashcards
What types of substances can get through the blood-brain barrier?
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
resting potential
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
depolarisation
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.
hyperpolarisation
is a change in membrane potential. Measured using patch clamping that allows them to record ion currents passing through individual channels
serotonin
mood and temperature regulation, aggression, and sleep cycles
dopamine
motor function and reward
acetylocholine
muscle contraction (PNS), corticol arousal (CNS)
glutamate
main excitatory neurotransmitter; participates in relay of sensory info and learning
GABA
main inhibitory neurotransmitter
anandamide
pain release, increase in appetite
norepinephrine
brain arousal and other functions like mood, hunger, and sleep
Which neurotransmitter’s site does nicotine occupy? How does nicotine use produce psychological reward?
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
What are the main effects of alcohol on neurons in the brain?
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
Which type of neurotransmitter’s receptors does cannabis target?
CB1 receptor – common g-protein linked receptors in the brain
CB2 receptor – CNS and immune system
Endocannabinoids – neurotransmitters (e.g., anandamide)
Which neurotransmitter’s action is affected by cocaine? How?
Blocks dopamine transporters (responsible for reuptake)
what neurotransmitters are involved in euphoria
Endorphins: These neurotransmitters than inhibit the transmission of pain signals and promote feelings of euphoria.
Opiates can also offer analgesic effects? What do they do to cells in the pain pathways to reduce pain transmission?
?
If a drug is ingested, what’s the most likely place of absorption?
- Easy and relatively safe
- Mostly intestinal absorption
- Absorption via digestive tract unpredictable
if a drug is inhaled?
• Absorbed through capillaries in lungs
Why is intravenous injection of a psychoactive drug highly effective?
into veins, drug delivered directly to brain
drug tolerance
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
effect selectivity
tolerance forms to some but not all effects of drug
cross-tolerance
may extend to other drugs that work by similar means
functional tolerance
(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
metabolic tolerance
Less of the drug gets to sites of action
why do withdrawal symptoms tend to be the opposite of the initial effects of the drug
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.
contingent tolerance
differential tolerance to the anticonvulsant, hypothermic, and ataxic effects of ethanol.
hypothermic effects of alcohol
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
How is addiction different from drug dependence?
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
What are the problems with physical dependence theories of addiction?
Can’t explain:
• Addicts relapse long after detoxification
• Individuals begin using drugs
• Addictions develop to drugs that do not produce severe withdrawal symptoms
incentive-sensitisation theory
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.
