CJH332H1 Lecture Notes - Lecture 14: Dentate Gyrus, Voltage Clamp, Reversal Potential
Lecture 14: Eliminating Synapses and Memory
• Within hippocampus, two groups (dentate gyrus and schaffer collaterals)
- LTP or LTD in the synapses here are possible
• AMPA mediated response – they are the ones measured when synapse
strengthened or weaker (1/3 different ionotropic glutamate receptors)
Glutamate
• LTP involved in insertion of AMPA or AMPA staying open longer
• Thought to be postsynaptic (different from short term plasticity – wont see them at the synapse after time)
- Short term related to presynaptic Ca rather than number of receptors or phosphorylation of receptors
Glutamate responses before and after
• At the reversal potential (current inside to outside = 0), it cannot be
one ion acting on this (unlike leak channels)
• The various ions are the ones involving AMPA receptors
• Glutamate binds both receptors (AMPA/NMDA)
- AMPA receptors are responsible for peak amplitude
- NMDA receptors are responsible for late phase (slower opening)
• There are multiple components (IV curve) – AMPA peak amplitude IV
curve gives a linear characteristic and late phase/at rest, different
- At rest, NMDA is closed by Mg
- As cell depolarizes, there is a slow opening and
influx by NMDAR
• Voltage clamp reveals early and late currents mediated
by AMPA and NMDA
• Proof of these components through various antagonist
Specific blockers reveal specific roles
• APV is a NMDAR blocker – has the biggest effect on the
late phase (late phase disappears)
• CNQX is a AMPAR blocker – has the biggest effect on the peak amplitude/early phase (early phase disappears)
Contextual conditioning
• Groups of neurons that have been stimulated over and over again, with
strengthened synapse, store memory (eliminating neurons/synapse may erase
the memory)
• Habituation – free to move around the box, accustomed to environment
• Conditioning – tone and footshock coupled (learned association by freezing)
• Testing – affect memory (identify neurons involved remembering these tasks,
can we have the mice to go back to moving freely?)
Powerful technique
• Concept that groups of neurons AND their strengthened synapses form a memory (engram)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture 14: eliminating synapses and memory: within hippocampus, two groups (dentate gyrus and schaffer collaterals) Ltp or ltd in the synapses here are possible: ampa mediated response they are the ones measured when synapse strengthened or weaker (1/3 different ionotropic glutamate receptors) Ltp involved in insertion of ampa or ampa staying open longer: thought to be postsynaptic (different from short term plasticity wont see them at the synapse after time) Short term related to presynaptic ca rather than number of receptors or phosphorylation of receptors. Ampa receptors are responsible for peak amplitude. Nmda receptors are responsible for late phase (slower opening: there are multiple components (iv curve) ampa peak amplitude iv curve gives a linear characteristic and late phase/at rest, different. At rest, nmda is closed by mg. As cell depolarizes, there is a slow opening and influx by nmdar: voltage clamp reveals early and late currents mediated by ampa and nmda, proof of these components through various antagonist.
