neurochemistry and drug addiction
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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