kenyon neurotransmission 2 Flashcards
four types of receptors
channel linked receptors
enzyme linked
GPCR
intracellular receptors (for unconventional NTs)
ionotropic receptors also known as
ligand gated ion channels or channel linked receptors
ionotropic receptor structure
single transmembrane multimeric protein that binds to NT and is the channel
how do we get functional diversity in ionotropic receptors?
by mixing and matching subunits we can produce hundreds of types.
for each receptor, we can combine 4-5 different subunits for that particular receptor
metabotropic receptors aka
GPCR
metabotropic receptor fxn in terms of ion
-Binding of NT activates trimeric G-proteins; these G proteins directly and indirectly influence the opening and closing of ion channels
(along with a thousand other activities).
define orphan receptor
a 7-transmembrane protein that looks like a metabotropic receptor, but we dunno what is its ligand
muscarinic and dopamine and adrenergic,
glutamate and GABA,
histamine and serotonin, and purine receptors are part of what class?
metabotropic!!!!
metabotropic receptor functional diversity
DON’T MIX AND MATCH
but the respective G protein pathways are basically unlimited
ionic power of metabotropic receptor
EPSP or IPSP, not huge action potentials
ionic power of ionotropic receptors
- minor change of membrane potential
- but if Ca++ flows through, it can initiate an AP
ELR (enzyme linked receptor) mech
NT activates a tyrosine kinase that (1) directly or (2) indirectly opens or closes ion channels.
also does a bunch of other stuff
intracellular receptors are mainly for?
unconventional NTs
list the major small molecule NTs (4)
ACh
AAs(glutamate, aspartate, GABA, and glycine)
Biogenic amines (catecholamines, sertonin, and histamine)
Purines (ATP, ADP, and adenosine)
ACh locations
- neuromuscular junctions
- preganglionic autonomic ganglia
- post-ganglionic parasympathetic
- many CNS neurons
how does ACh get made?
@presynpatic terminal
acetyl coA + choline —–> acetylcholin
^^^key enzyme: choline acetyltransferase
how does ACh get deactivated?
happens in the synaptic cleft
gets inactivated by ACETYLCHOLINESTERASE
How does the choline get recovered?
Na+/choline antiporter on the presynaptic terminal
Nicotinic AChR (Nm and Nn) are what kind of receptors?
IONOTROPIC!!!!
How conserved are the Nm or Nn receptors?
Nm = VERY conserved
Nn = TONS of kinds (combine 4-5 subunits!)
muscle nAChR types of subunits
both Nm and Nn have the same three subunits
-alpha 1, alpha 1, beta 1
differ in the last two subunits
- fetal mammals and torpedo: gamma and delta
- adult mammals: delta and epsilon
things that bind to the a1 subunit on Nm
ACh, nicotine, curare, bungarotoxin
Neuronal NAChR structure
still pentamers
alpha subunits: 1-10
beta subtunits: 1-4
a7: are Ca++ channels
What does this mean?
lots of room for diverse pharmacology
targets for skeletal muscle nACh receptors
curare, d-tubocurarine, succinylcholine, and alpha bungarotoxin