Lecture 6 - Psychopharmacology Flashcards
What are the 2 receptor types for synaptic action? List & briefly describe
- Ionotropic
- n.t.’s bind RIGHT ON the channel & that opens up an ion channel; allowing ions to come in - Metabotropic
- receptor site for n.t. is off site; operating through a 2nd messenger system, which will open for a foreign channel
Being a neurotransmitter: What does it take?
- Exists pre-synaptically.
- Released in response to action potential.
- Application at synapse produces response.
- post-synaptic membrane has receptors. (excit. or inhib.)
- Blocking release stops synaptic function. (stop activity @ synapse)
Psychopharmacology:
The study of the effects of drugs on the nervous system and on behaviour.
Drug effects:
The changes a drug produces in an animal’s physiological processes and behavior.
What is a ‘drug’?
- a very vague term.
- all ingested substances alter bodily function.
- ‘drug’ is reserved for things that have pronounced effects when ingested in small quantities.
Sites of Action:
The locations at which drugs interact with cells of the body, thus affecting some biochemical processes of these cells.
What is the basic classification of drug actions?
- Agonist
2. Antagonist
Agonist:
A drug that facilitates the effects of a particular neurotransmitter (excit. or inhib.) on the postsynaptic cell.
Antagonist:
A drug that opposes or inhibits the effects of a particular neurotransmitter (excit. or inhib.) on the postsynaptic cell.
What is the difference in the role of n.t. & the drug?
n. t. will determine if there’s an excit. or inhib. effect on the cell, the drug will make it easier (agonist) or harder (antagonist) for that drug to have its effect
ex) if a n.t. normally has an inhib. effect, an agonist would make it easier for that inhib. effect to happen & an antagonist would make it harder for that inhib. effect to happen
Agonist drug effect
- agonist drug binds to the receptor site
- enhanced cellular activity
more receptors being activated, more channels being open, it increases the effect
Antagonist drug effect
- plugging receptor sites, but not opening the channels & causing natural n.t. to not be able to bind at those sites
- block or reduce cellular activity b/c you’re letting n.t. act at fewer receptor sites
Ways that drugs can agonize
- precursor to neurotransmitter
- L-DOPA is a precursor to dopamine that can cross BBB, that convert to dopamine in brain - stimulate release
- more n.t. released in synapse, more likely the effect on PS membrane & increased effect of that n.t. - receptor binding
- & open channels - block autoreceptors
- cells keeps pumping out n.t. - acting like an agonist (b/c signal to slow down doesn’t happen) - inhibition of reuptake
- n.t. can keep operating at synapse - having an agonist effect - inhibition of deactivation
- acetylcholinesterase breaks down ACh
- if we inhibit, we allow n.t. to act longer in the synapse
What are autoreceptors?
- receptors on pre-synaptic membrane
- monitor amount of n.t. in synapse
- normally when things bind to them, they’ll cause slow down of release of n.t. b/c it will be a sign there’s enough n.t. b/c its feeding back on itself
Ways that drugs can antagonize
- prevent synthesis
- have a drug that blocks synthesis of L-DOPA –> dopamine - prevents storage
- less n.t. released into synaptic cleft - block release
- can’t do it’s job if it’s not being released in the pre synaptic - receptor blocker
- plugs imitate preventing a possible binding site for n.t. - stimulates autoreceptors
- starts reuptake too early, presynaptic cell is getting a signal theres so much n.t. in synapse that its binding to me (artificially fooling)
What are 2 different Drug Actions at Binding Sites
- Competitive Binding
- Binds at same site neurotransmitter would. - Noncompetitive Binding
- Binds at different site.
BOTH can have agonist & antagonist effects
What are the four major neurotransmitter systems?
- Acetylcholine
- Dopamine
- Norepinephrine
- Serotonin
Acetylcholine
- active in maintaining waking electroencephalographic (EEG) patterns of the neocortex
- thought to play a role in MEMORY by maintaining neuron excitability
- death of acetylcholine neurons & decrease in acetylcholine in the neocortex are thought to be related to ALZHEIMER’S DISEASE
- produced in the BASAL FOREBRAIN NUCLEI & MIDBRAIN NUCLEI
Where is Acetylcholine produced?
produced in the BASAL FOREBRAIN NUCLEI & MIDBRAIN NUCLEI
Dopamine
- active in maintaining normal MOTOR behaviour
- loss of dopamine is related to PARKINSON’S DISEASE, in which muscles are rigid & movements are difficult to make
- increases in dopamine activity may be related to SCHIZOPHRENIA
- produced in the SUBSTANTIA NIGRA
Where is Dopamine produced?
- produced in the SUBSTANTIA NIGRA
Norephinephrine
- active in maintaining EMOTIONAL tone
- decreases in norepinephrine activity are thought to be related to DEPRESSION, whereas increases in it are thought to be related to MANIA (overexcited behaviour)
- produced in the LOCUS COERULEUS
Where is Norepinephrine produced?
- produced in the LOCUS COERULEUS
Serotonin
- active in maintaining waking EEG patterns
- increases in serotonin activity are related to OBSESSIVE-COMPULSIVE DISORDER, TICS, & SCHIZOPHRENIA
- decreases in serotonin activity are related to DEPRESSION
- produced in the RAPHE NUCELI
Where is Serotonin produced?
- produced in the RAPHE NUCELI
Amines
Modulatory effect on systems
Monoamines
- catecholamines (dopamine, norepinephrine)
- indoleamines (serotonin)
Quaternary amines
- Acetylcholine
Information transmitters
amino acids (glutamate, GABA)
learning - info transfer
Acetylcholine functions
- muscular movement
- high during REM sleep
- learning
- memories
Acetylcholine produced
Cholinergic pathways in the brain - basal forebrain, dorsolateral pons. (producing ACh)
Acetylcholine how it’s made
Acetyl-CoA & Choline mix & ChAT transfers acetate ion from acetyl-CoA to choline - all together form CoA & ACh
Dopamine description
- metabotropic receptors
- Amphetamines alter dopamine uptake and produce schizophrenic-like delusions.
- can see similar effects with cocaine use.
- Parkinson’s disease – degeneration of the nigrostriatial dopamine system.
Amphetamines
alter dopamine uptake and produce schizophrenic-like delusions.
- stimulant
- cause release of n.t. dopamine - activates receptor molecules
- may also interfere with reuptake process (blocks)
- but continues to activate it’s receptors
Cocaine
- blocks reuptake of dopamine
- dopamine continues to activate its receptors
- constant use can lead to large amounts of dopamine in synaptic cleft
- esp. paranoia
Parkinson’s disease
degeneration of the nigrostriatial dopamine system.