PA20023 Flashcards
What receptors are at inhibitory synapses?
Ionotropic receptors
neurotransmitter can Hyperpolarise the cell, and therefore inhibit from receiving further action potentials.
Hyper-polarisation is through chloride ions
What receptors are found at excitatory synapses?
Ionotropic
Transmitter interacts with receptors largely permeable to K+ and Na+
Eg acetylcholine binds to nicotinic ionotropic receptors at excitatory synapses creating an EPSP
Which is faster at generating an action potential, spatial summation or temporal summation?
Spatial
When cells are close together, their action potentials can add up to reach threshold; many cells firing at Same time and their action potentials add up.
Whereas temporal is one cell firing in succession to try and generate an AP
Where are purkinje, pyramidal and the motor neurone found?
Purkinje neurones found in cerebellum
Pyramidal neurones found in cortex
Motor neurone is the big neurone in the spinal cord
Are endorphins (endogenous opioids) amino acids, purines, amines or peptide neurotransmitters? what about adenosine?
Endorphins are Peptides
Adenosine is a purine
GABA A and B, which one binds to ionotropic receptors?
GABA a binds to ionotropic
GABA b binds to GPCRs
What are EAATs?
Excitatory Amino acid transporters
They facilitate glutamate reuptake at synapses
Present in glial cell membranes and presynaptic cell membrane to allow glutamate reuptake, stored as glutamine in glial cells
What is monosodium glutamate?
A flavouring In food
It can actually kill some brain cells
Glutamate is involved with exctitoxicity
How is glutamate stored in order to regulate its levels In the CNS?
Stored as glutamine in the Glial cells that sit in between neurones, it is synthesised from glutamine by phosphate activated glutaminase enzyme within a presynaptic cell when it’s needed
How does glutamate bind to so many receptors?
It is flexible, it can rotate around its alpha beta and beta gamma bond.
At least 9 different rotamers are possible
The __ elements of ionotropic receptors form the pore. How?
P elements
They are part of each of the 4 subunits that form these receptors, they’re subunit 2. They associate and bring the subunits all together in an orientation that forms a pore/ channel.
what subunit is present in the AMPA receptor will make it impermeable to calcium? When is it permeable to calcium?
GluA2 subunit present= not permeable to Ca
Homomeric GluA1 receptor= is permeable to Ca
Remember it’s also permeable to Na+ in and K+ out
Is NMDA receptor permeable to calcium? How does is compare to the AMPA receptor?
Vastly permeable to calcium, doesn’t depend on subunit composition like AMPA.
It lets more calcium in than AMPA even when it is permeable
What is a co-agonist of the NMDA recpetor?
Glycine
NMDA receptor can only be activated when glycine is present
You need another agonist too; NMDA, glutamate, aspartate
The different properties of the AMPA and NMDA receptors give the fast and slow time course of an EPSP. Which does which?
AMPA: fast on fast off (fast depolarisation)
NMDA: slow on slow off (slow depolarisation)
NMDA receptors are dual gated, what does this mean?
They’re both voltage gated an ligand gated.
The channel of NMDA is blocked by Mg2+, which only moves when depolarisation occurs.
NMDA receptor needs both glutamate and depolarisation to work
What effect do mGluRs have on calcium, and on glutamate release?
mGluRs are metabotropic receptors
In presynaptic cells they lead to calcium channel closure, which leads to less glutamate release.
In postsynaptic cells they lead to K+ channel closure.
This leads to reduced K+ efflux out of the cell and slow depolarisation
Also glutamate binding to mGluRs in postsynaptic cell leads to an increased level of intracellular calcium.
What two receptors are involved with glutamate release control?
Presynaptic NMDA (ionotropic) and presynaptic mGluR’s.
Presynaptic NMDA r increases glutamate release by increasing calcium influx.
Presynaptic mGLuRs decrease glutamate release by decreasing Calcium influx
GABA is synthesised from _____.
The enzyme that catalyses this is _____.
GABA is further converted into _____, by the enzyme ____.
Drugs acting on these enzymes to increase levels of GABA can be used as _______.
Synthesised from glutamate
By the enzyme glutamic acid decarboxylase
Further converted to succinate
By the enzyme GABA transaminase
Drugs acting on these enzymes can be used as anticonvulsants in epileptics, as GABA is inhibitory.
GABA a receptor (ligand gated ion channel, ionotropic) agonists?
GABA B receptor (GPCR) agonists?
GabaA: agonists are GABA and Muscimol
GABA B: agonists are GABA and baclofen
What is baclofen used to treat?
Muscle spasms
It binds to GABA B receptors
Inhibits motor neurone activation via the spinal cord
Major side effect: sedation, as baclofen crosses the BBB, inhibits brain activity making you sleepy
Where do benzodiazepines act?
They can be agonist or inverse agonists of the modulator site of GABA A receptors.
They’re allosteric modulators, and they bind at the interface between the alpha and gamma subunits of the GABA A receptor.
GABA binds between the alpha and beta subunits
What are benzodiazepines actions?
Multiple actions
Bind to GABA A so have inhibitory effects
Anxiety relieving, anticonvulsant and Hypnotic.
Note: they can be agonists, antagonist and inverse agonists
What are etomidate and propofol? Where do they act?
Anaesthetics
Act at GABA A receptors
Cross BBB and inhibit brain neuronal activity, making you sleepy
What effects do barbiturates and phenobarbital have?
Sedative/ anti convulsive
Calm down muscle activity
They can increase inhibition of nervous activity in the brain to the point of death
Remember barbiturates act on GABA A receptors, they’re channel modulators and stimulate the receptor to further inhibit motor pathways
What do Neurosteroids bind to?
Bind to GABA receptors
Metabolites of progesterone & deoxycortisone
Where does ethanol ( Alcohol ) bind in the CNS?
Binds to GABA A receptors
Alcohol has a depressant effect on the CNS
It increases GABAnergic inhibition
Diazepam and lorazepam are Benzodiazepines. How do they make you feel?
They are calming
They are anxiolytics (anti anxiety)
They are NOT sedative
Nitrazepam, flurazepam and temazepam are all Benzodiazepines. How do they make you feel?
They’re hypnotic
So they makes you fall asleep
Used to treat insomnia
Remember benzodiazepines act on GABA A receptors, they’re channel modulators and stimulate the receptor to further inhibit motor pathways
Dopamine, 5-hydroxytryptamine, acetylcholine and norepinephrine are all examples of _____________.
Neuromodulators
They modulate GABA and glutamate
Neuromodulators are not reabsorbed by the presynaptic terminal or broken down. They’re neurotransmitters that modulate
How does amphetamine give its stimulatory effects?
It blocks reuptake of Nor adrenaline by NETs( Norepinephrine transporters), amphetamine is also a substrate for these transporters, and can be uptaken into the presynaptic cell, where it can stimulate Nor adrenalin release from vesicles.
Nor adrenaline excites neurones
Amphetamine can therefore increase wakefulness, but can be abused as a performance enhancer
What is L dopa used to treat?
Parkinson’s
Increases synthesis of noradrenaline
Similar structure to dopamine
More noradrenaline= more Neuromodulators, more muscle movement control.
What drug blocks Vesicular uptake of Nor adrenaline and 5HT and therefore decreases Their levels? What condition can this lead to?
Reserpine
This can lead to depression
Dopamine links to both Parkinson’s and schizophrenia. How? What pathways are involved?
Parkinson’s:
Nigrostriatal pathway disrupted without dopamine(from sustantia nigra to striatum) Leads to lack on control of movement- parkinsons
Schizophrenia:
Mesolimbic/ mesocortical pathway (from VTA to cortex & hippocampus) disrupted without dopamine. This pathway is involved with emotional, reward and attention, leads to schizophrenia
What three types of things can be used to treat Parkinson’s?
L dopa
MAO inhibitors
COMT inhibitors
All increase levels of dopamine
What are psychotropics used for?
These block dopamine receptors
Prevents dopamine binding to its receptors
Used to treat manic phases of schizophrenia
But result in Parkinson’s like side effects like shakes and tremor due to lack of dopamine
5-HT controls feeding, what does and increase and decrease in 5HT cause?
Increase in 5-HT: loss of appetite, weight loss
Decrease in 5-HT: feeding, hunger, weight gain
(opposite to what you may expect)
What is 5-Hydroxy tryptamine synthesised from?
Tryptophan
Hydroxylation by tryptophan hydroxylated
Then decarboxylated by 5HTP decarboxylase
5HT then transported into vesicles by VMAT
Which can become saturated; tryptophan hydroxylase in 5-HT synthesis or tyrosine hydroxylase in noradrenaline synthesis or choline acetyltransferase in Acetylcholine synthesis?
Tyrosine hydroxylase
Once it’s saturated no more nor adrenaline can be produced from tyrosine
With 5HT and acetylcholine synthesis, the amount of precursor present is raged limiting, not amount of enzyme, as these will not become saturated
How do SSRIs work?
Block the reuptake of 5-HT back into presynaptic cells
What neurotransmitters get transported into their vesicles by VMAT?
VMAT is vesicular monoamine transporter
5 HT, dopamine, noradrenaline
Acetylcholine is NOT
What is each monoamine neurotransmitter involved with (eg arousal, feeding, motivation..)
Noradrenaline: arousal/alertness Dopamine: reward + motivation 5HT: appetites chemical Acetylcholine : memory/ motivation Histamine: sleep, feeding, energy balance
What does diphenhydramine (Benadryl) do?
Binds to histamine receptors, it’s a H1 antagonist, so its an antihistamine (anti allergy) it’s sedating though as it crosses the BBB.
Newer antihistamines don’t cross the BBBand are H2 antagonists
What disorders are each of the 4 monoamine neurotransmitters Important in?
Noradrenalin and 5HT important in depression
Dopamine is important in schizophrenia, Parkinson’s, and drug addition
Acetylcholine is important in Alzeihmers
How does cocaine have its effects?
Reuptake inhibitor of Noradrenaline and dopamine
Binds to reuptake transporters and blocks them
What axis plays a role in maintaining stress responsiveness?
The hypothalamic pituitary axis
It’s releases ACTH (adreno cortico tropic hormone) which stimulates the adrenal gland to release cortisol, a stress hormone, involved with fight or flight response
Cortex, hippocampus, hypothalamus, amygdala, basal ganglia / cerebellum. What are these five parts of the brain involved in?
Cortex: negative cognition: ie having a bad feeling towards something
Hippocampus: Involved with memory
Hypothalamus: stress response
Amygdala: fear perception
Basal ganglia/ cerebellum: movement/ control
What CNS disorder can beta blockers be used to treat ?
Anxiety
Especially panic attacks
Target autonomic symptoms (ones you can’t control) eg rapid heart beat, raised blood pressure)
What drug treats general anxiety disorder?
Busiprone
A benzodiazepine, full agonist at GABA A which causes sedation, useful for sedation before operations?
Midozalam
A benzodiazepine, partial agonist, known as a positive modulator of Cl channels of GABA A receptors? What about a partial inverse agonist?
Partial agonist: RO16-6028: positive modulator, increases inhibition therefore relaxes
Partial inverse agonist: RO15-4513: negative modulator, decreases inhibition therefore stimulates
A competitive antagonist of the GABA A receptor, which is good for reverse respiratory depression?
Flumazenil
A benodiazpeine, An inverse agonist at the GABA A receptor?
DMCM
What are Midozalam, bromazepam, clonazepam, diazepam and flunitrazepam all?
Strong agonists of the GABA A receptor, therefore they’re all anxiolytics (anti-anxiety) they relax and sedate
Which benzodiazepines are hypnotics?
Temazepam Loprazepam Nitrazepam Flurazepam They're used to treat insomnia
What do all benzodiazepines end in?
-am/pam
Eg Midozalam, temazopam, diazepam
Benzodiazepines:
2 Keto drugs: ____ half life
3 hydroxy and triazolo drugs:_____ half life
2 keto drugs: long half life
3- hydroxy and Triazolo drugs: short half life
If a patient is prescribe a benzodiazepine, why shouldn’t they drink alcohol?
Alcohol is ALSO a CNS depressant
Therefore they would interact
2 CNS depressants= too much inhibiton= can result in a COMA
Remember benzodiazepines are ANXIOLYTICS, not antipsychotics!!
People can become physically dependent on them, therefore you should “taper off” dose when coming off them
What does an EEG record?
Records activity of populations of neurone in the brain, records brainwaves. Uses electrodes recording on scalp. Detects electrical activity produced when afferent axons synapse and release glutamate.
How do we coordinate between rem and non rem sleep?
Cholinergic neurones increase their firing rate to start off phases of REM sleep.
Nor adrenaline neurones increase their firing rate when non REM phase starts. These two neurones work together.
We also have REM on and REM off cells
What could be used as a cure for jet lag to get body clock back on track?
Melatonin, derived from 5HT
It has it’s own circadian rhythm
What three substances regulate your body clock and help your sleep?
Interleukins
Melatonin
Hypocretin/orexin
What is narcolepsy?
A disorder where people are unable to regulate their sleep/ wake cycles