Lecture 3: Synapse Plasticity II

Question 1

What can be used to measure glutamatergic synaptic transmission using electrophysiology?

Answer 1

Field recordings/extracellular recordings

Patch clamping/whole cell recordings

Question 2

Describe how electrophysiology is used to measure synapse function

Answer 2

It gives a measure of synapse function using transmitter release and postsynaptic current flow through receptors. When the presynaptic axons are electrically stimulated, presynaptic axons will fire action potentials and release glutamate from presynaptic terminals. The glutamate receptors which are located postsynaptically will open and conduct current through ion flow. This current is measure electrophysiologically using a recording electrode.

Question 3

Field recordings/ extracellular recordings

(What does it measure)
(How is it used and how does it measure)

Answer 3

• give a measure of the strength of synapses of a population of neurons
• recording electrode is placed between the postsynaptic neurons and the presynaptic axons
• it measures the loss of positive ions as they move into the postsynaptic neurons (intracellularly) from the extrasynaptic space (extracellularly)

Question 4

Whole cell recording/ “patch clamping”

(What does it measure)
(How is it used and how does it measure)

Answer 4

It measures the strength of synapses of an individual neuron

The recording electrode is stuck onto the neuron and it measures the current flow into it.

Question 5

What happens when there is an influx of positive ions (Na+) into the postsynaptic neuron

Answer 5

An excitatory postsynaptic potential is induced which is a temporary depolarization of the postsynaptic membrane

Question 6

What happens when there is an influx of negative ions (Cl-) into the postsynaptic neuron

Answer 6

An inhibitory postsynaptic potential is induced which is a temporary hyperpolarisation of the postsynaptic membrane

Question 7

Describe an electrophysiology rig

Answer 7

Record electrical responses of a sample (using amplifiers or remote electrode manipulators)
Look at samples (using microscope)
Drug inflow lines (to stop other transmitters or block receptors)
Keep sample alive in physiological relevant conditions (such as heated bath, artificial (saline) cerebrospinal fluid solution)

Question 8

In AMPA receptor - mediated excitatory postsynaptic current (EPSC), inflow of cations means that

Answer 8

Amplifier needs to deliver more negative current to hold -65mV (resting membrane potential).

Question 9

Synapse plasticity

Answer 9

The ability of synapses to change their strength (increase/decrease) based on specific neuronal stimulation

“Cells that fire together, wire together”

Question 10

Long term potentiation (LTP)

Answer 10

Stimulation that leads to increased synaptic strength

Question 11

Long term depression (LTD)

Answer 11

Stimulation that leads to decreased synaptic strength.

Question 12

Synapse plasticity (LTD and LTP) are though to underlie

Answer 12

Declarative memory (names, objects, facts)

Question 13

Region of the brain in the temporal lobe that is important for declarative memory

Answer 13

Hippocampus

Question 14

The hippocampus has a very simple architecture and organization that allows

Answer 14

Specific axonal paths stimulation and specific postsynaptic pyramidal cell recording

Question 15

The trisynaptic loop of the hippocampus

Answer 15

1. Perforant pathway: entorhinal cortex to dentate gyrus neurons
2. Dentate gyrus neurons to CA3 pyramidal cell neurons
3. CA3 pyramidal cell neurons to CA1 pyramidal cell neurons.

Question 16

Dentate gyrus neurons
(Cell body name and axon name)

CA3 pyramidal neurons
( soma and axons name)

Answer 16

Dentate gyrus neurons
(Granule cell and mossy fibres)

CA3 pyramidal neurons
(CA3 pyramidal cell and Schaffer collaterals)