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32 Cards in this Set
- Front
- Back
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actions of drugs at GABA synpases |
GABAergic transmission in the CNS GABA receptors |
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what is gaba |
inhibitory synaptic neurotransmitter- every nerve cell in CNS has multiple inputs and outputs found exclusive in brain tissue high conc found in striatum, substantial niagra, hippocampus, globus pallidus and many other areas extremely high amount of GABA in the brain |
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only pathway in CNS is to where |
STR TO SN |
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explain gabaergic neurotransmission |
created and stored in nerve terminals in synaptic vesicles removed by transport processes, taken back to nerve terminals |
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GABA effects in the CNS |
Presynaptic inhibition postsynaptic inhibition |
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explain presynaptic inhibition |
GABA is inhibitory in the spinal cord reduces transmitter release from terminals of primary afferent fibre pharmacological distinct from glycine |
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what happens with gaba is released in presynaptic inhibition |
when GABA is released it acts on the nerve terminals and suppresses them and stops them releasing neurotransmitter GABA is a modulator and regulator |
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post synaptic inhibiton |
most GABA EFFECTs in brain increase chloride flux postsynaptically more important than pre synaptic if open a chloride ion channel it stabilizes the membrane and makes it resistant |
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explain example of GABA Inhibition of dopamine neurone firing in substantia nigra |
modulate firing of dopaminergic neurons too much activity on the dopaminergic pathway can cause GABA release, indirectly inhibit the firing of the dopaminergic pathway feedback loop keeping the lever of dopimergic pathway at a level, too high gaba is released too low gaba stops being released |
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what else is an example of postsynaptic inhibition |
external and recurrent inhibition of pyramidal neurones in cerebral cortex and hippocampus |
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explain what happens in external and recurrent inhibition of pyramidal neurones in cerebral cortex and hippocampus |
recieving massie input too much from input sends a excitatory signal to gaba which in effect dampens it down |
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what is recurrent inhibition |
stimulate incoming pathway axon co-lateral prevents bursting discharge drug effects |
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give a example of recurrent inhibition |
bicuculline blocks the recurrent inhibition produced following stimulation of the afferent pathway |
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explain the bicuculline recurrent inhibtion |
not stimulating you still see an output if you stimulate input you will get a spike in output then it disappears (thats recurrent inhibitors) spike is then blocked |
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binding of GABA TO BRAIN IS WHAT |
Saturable and specific |
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name 2 main classes of binding sites |
GABA receptors GABA uptake site |
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explain GABA RECEPORS and GABA uptake sites |
gaba receptors- binding is not sodium dependent gaba uptake site- greatly outnumber GABA Receptor sites neuronal and non-neuronal binding is sodium dependent |
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how to make GABA receptors more specific |
dont use sodium so we know its not the uptake sites |
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what does Bicuculline do |
displace GABA but not from sll receptors |
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what does picrotoxin do |
does not displace gaba acts at different site from GABA binding site binds to chloride channel part of GABA RECEPTOR barbiturates also acts at the picrotoxin site |
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two subclasses of GABA receptors |
GABA A- bicuculline sensitive baclofen-insensitive GABA B- bicuculline insensitive baclofen- sensitive |
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how to get from GABA receptors to the subtypes |
GABA receptors ionotropic(chloride ion channels) to GABA or GABA Receptors to metabotrophic to G-protein coupled GABA B |
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explain about GABA A receptor |
pentamer ligand gated ion channel subunits are standard 4 TM structure GABA binding site is on a Beta subunit BDZ binding sure is on a alpha subunit |
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explain GABA A receptor |
1 subunit crosses membrane 3!58’es pore lining region |
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every GABA receptor is made from what |
2 alpha, 2 beta and 1 other/gamma |
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what is there in gaba binding |
2 interfaces between alpha and beta subunits |
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what is there in benzodiazepine binding |
interface between alpha and gamma subunits |
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GABA had to bind twice to complex receptor to do what |
activate itw |
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explain characteristics of GABA A-p receptors |
similar structure to GABA a receptor 5-subunit ligand gated ion channel found in retinal bipolar cells different pharmacology to GABAA receptor |
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explain GABA b receptor |
metabotropic receptor heterodimer of two 7TM receptors there is GABA b1 and GABA b2 B2 binds to positive modulators couples to GI/Go |
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GABA b effects |
presynaptic: decreased Ca2+ fluxes post synaptic- increae in K+ fluxes implicated as target for management of - pain, absence epilepsy,cocaine addition, asthma |
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what are the two typical benzodiazepines |
chlordiazepoxide diazepam |
