cc 6 Flashcards
evidence for LTD in slices
Ito (1984)
benefits of in vitro
steel removes vibration, limits animal movement and blood flow limited, can be kept for a long time
How to get LTD in slice
Stimulate PF - record from PC.
Pair PF and CF
Then stimulate PF alone= reduction in PC response.
LTD.
EPSPs
summate to produce an action potential
LTD makes EPSPs smaller
What kind of synapse is PF - PC
glutamate is the neurotransmitter. Two types:
- ionotropic - AMPA receptor: when activated opens ion channels allowing flux of NA
- metabotropic - mGLuR1. when activated act on signalling machinery in cell.
possible mechanism of LTD
- parallel fibre activates both AMPA and mGluR1 receptors
- mGluR1 activation starts a cascade of processes in the cell
- if the climbing fibre also fires, this cascade continues until some AMPA receptors are removed
- removal of AMPA receptors reduces ampliude of EPSPs induced by parallel fibre stimulation - LTD
Whats the problem?
slices are unnatural- no afferents, no blood supply : Can we assume that processes observed in slices are present in the intact brain
2. even if LTD in slices were present in the intact brain might not be there for learning - might have a protective function (De Schutter 1995)
Schonewille 2011 - knockout mice
breed mutant mice that lack necessary cellular machinery.
* Lack LTD in slices but show nrma eyyeblink conditioning
why do knockout mice show normal eyeblink condiitoning
lJohansson 2015
Training produces a pause in simple spike firing.
This pause is still present after mGluR1 blocked.
NOT present ater blocking mGluR7.
- Ampa not involved at all.
- mGluR7 act on a protein that activates a potassium channel
- inhibits purkinje cell,
However: LTD can be obtained in mutants if induction procedure changed
Raises important issure of in vitro results.
