Final: Chapter 9 Flashcards
What are the 3 methods of refinement?
1) Refinment topography
2) refine convergence
3) refine postsynaptic compartment
Refine Topography
correct location, but too far
Refine convergence
remove connections
Refine postsynaptic compartment
innervates soma and dendrites, then backs off dendrites
Decrease in convergence means you eliminate…
input
in young neurons, increase based on how many neurons coming in, adult neuron has calmed it down, just takes 1
Experiment: hippocampus crossing corpus C.
cells don’t die, but they will eliminate connections after crossing
How do we image the cat brain?
3H proline
Retina: label aa, inject into cell, vesicle release chain to thalamus to cortex
white in photos: becomes organized swirl
Experiment: cover primate eye
uneven left and right eye territory
need to use eye to keep competition
Experiment: labeling with horseradish (HRP): what are the two steps in reducing retina ganglion cell terminates in LGN?
1) PRENATAL loss of branches in wrong layer
2) POSTNATAL: loss of extra branches
Why does refinement occur at NMJ?
can’t extend and flex at same time, not just about who has more, but who has the right connections.
Usage shows what is wrong with the system
Experiment: cat shut 1 eye at birth
monocular: one eye super long column
Thalamus doesn’t change, it’s the cortex that changes
Experiment: cat shut both eyes
similar to controls, most cell binocular
Experiment: shut 1 eye in adult
nothing happens, critical window, once window closed not plastic
Monkeys: ocular dominance:
anatomical decrease faster than physiology,
The Layer 4 morphology changes before the physiological response
What actually regulates critical period?
When GABA is inhibitory, critical window closes
Pirate mice
1) normal adult
2) pirate baby mouse
3) pirate adult
4) GAD 65 -/- adults
5) MGE cells (P10) transplant in adult
1/3- adults normal
2/5/6- shifted
GAD-/- = no inhibitory GABA
MGE cells= no inhibitory GABA
_______ leads to specificity of synaptic connections.
Synapse elimination
Axonal withdrawal = (more/fewer) postsynaptic cells innervated
fewer
Experiment: Strabismus Cat
not just the amount of activity, its the timing
can’t integrate L/R info.
NO SYNCHRONY
lose binocular connections
Graph look like two monocular bumps
How does strabismus cat alter cortical projection pattern?
loss of horizontal projections in layers 1-3, look like weird stripes now
Experiment: force frog to share tectum
not coactive, destabilizes so each eye gets own territory in tectum
based on surrounding activity
For you give NMJ TTX cuff and eliminate AP,
polyneuronal innervation remains
Experiment: NMJ, increase stimulation
Stimulate wrong contact
speed up process, lose MN connections
Stimulate wrong contact = wrong connection
Motor neuron elimination and distance
only competition is near by, if far enough apart, you can stimulate one and still not get elimination of the other
Stimulus orientation of lines is noted by different recordings from
primary visual cortex
Experiment: cat with line glasses
Better at vertical stuff than controls
Experiment: strobe light cat, only see stationary objects
worse than controls at detecting motion
Ferrets: reared in the dark
orientation diminished
motion direction detection is gone through
Different aspects of vision have different windows
Experiment: Frog eye rotate 180 degrees
location of stimulus moves, temporal of other eye synapse at new location
Experiment: Rats in clicking environment
no refinement
respond to broad range of frequencies and broader frequency tuning properties
Ruined topographical organization in cochlea
Remapping Owls: 23 degree prism glasses: Thinks mouse in front. 60 microsecond difference between ears hearing squeaks
inject tracer to ICC
optic tectum- where visual/auditory integrate
result: auditory map adjusts to the visual map.
normal experience essential for good synaptic refinement
Activity dependent development includes activations of
NMDA R and CAMK2
Heterosynaptic depression = (increase/decrease) in synaptic strength
decrease
_____ mediates alterations in synaptic strength
2nd Messengers
Spontaneous visual activity
Experiment:
1) Dark reared cat
2) TTX block cat
pattern until eyes open - helps ocular dominance
Spontaneous retinal activity = stripe formation in layer 4
TTX block = no stripe
Spontaneous activity: auditory
Experiment: isolate cochlea, use ATP antagonist
Normally, supporting cells release ATP, acts like NT, cells release glutamate
Eliminates spontaneous activity
Spontaneous activity: Cortex
Ca2+ signal caudal –> rostral
Ends when inhibitory synapse become hyperpolarizing
Heterosynaptic depression at NM synapse
LP vs. SN
Stim SN = muscle contraction, but Stim LP…
activity in one synapse depresses another
SN gives weaker muscle contraction. LP doesn’t change, but decreases the other
How does heterosynaptic depression work:
Stimulation: PKA and PKC
PKA: activated by ligand release with AcH, protects AChRs under active terminal
PKC: activated by Ca2+ influx, phosphorylates AChRs on inactive terminal
ProBDNF and synaptic withdrawal
retrograde signal.
proBDNF= synaptic depression, withdrawal from presynaptic target.
Block with p75NTR - synaptic depression and withdrawal
Experiment: UV light increases Calcium influx
1) UV + muscle, Ca2+ increase
2) Same, but add that presynaptic activity
1) synaptic depression
2) add presynaptic activity, no retrograde signal to depress
To activate, NMDA-R needs
1) depolarization to get Mg2+ block out
2) Glutamate
Experiment: 3 eyed frog
1) Control
2) NMDA block (APV/MK801)
3) NMDA receptor activation
1) lines
2) no lines
3) VERY distinct lines
increase NMDA = retinal terminal segregation
Dendrite synapse formation and CAMs
Activity = (more/less) CAMK2 due to ___
more CAMK2 due to Ca2+
CAMK2 phosphorylates ____ and ____ which results in…
DLG (synaptic protein)
Fas2 (cell adhesion molecule)
less adhesion, more sprouting.
Fas 2 not synaptic
Flies with increase cAMP have
decrease Fas2, more bountinal ends
LTD in development; what happens to it
Decreases as you develop. At first, low freq. stim has long lasting depression, then no effect
Depressed synapse
decrease colocalization of pre/postsynaptic elements
increased stability
equally likely to colocalize region
GABA transmission is need for normal inhibitory synapse formation, what happens in GAD67-/-
no GABA synthesis
lose inhibitory synapses because they aren’t functional, and don’t activate
synaptic activity/dendrite length: dendrite morphology depends on ___ contact
presynaptic
Postsynaptic targets are branchier when
more activity, used more
Experiment: cut NM affert axons at the midline
Golgi stain results?
Ventral dendrites shorter than those on dorsal side
Normally, dendritic spine mobility decreased, but in binocular deprived,
spine mobility increased, doesn’t like not activity at all, can’t lose everything, trying to bring it back
