Paper 3: Synaptic Transmission and Retrograde Messengers

Question 1

What is retrograde signalling?

Answer 1

first messenger molecule travels from postsynaptic cell to presynaptic cell in a chemical synapse

Question 2

What was the hypothesis of what was occurring in endocannabinoid-mediated synapses?

Answer 2

• if you depolarize postsynaptic cell, VG-Ca2+ channels in dendrites will open and allow Ca2+ ions into postsynaptic cell
• Ca2+ leads to synthesis of endocannabinoids
• hydrophilic endocannabinoids can pass through membranes or diffuse out of postsynaptic cell – will diffuse backwards across synaptic cleft, then bind to receptors on presynaptic cell (retrograde)
• endocannabinoids start metatropic signalling in presynaptic terminal, which leads to reduced neurotransmitter release

Question 3

What are paired patch recordings?

Answer 3

simultaneous whole cells recordings from neurons that share a synaptic connection

Question 4

What are autapses?

Answer 4

connections in which neurons synapses onto their own dendrites/somas

Question 5

What are the two organizing principle (two questions) for experiments in synapses and plasticity?

Answer 5

Question of Induction: Which compartment is the synaptic change being triggered from?
- Is the biochemical cascade that initiates the change in synaptic strength occurring in the presynaptic or the postsynaptic cell?

Question of Expression: Which compartment is altered to produce the change in synaptic strength?
- Is there more/less neurotransmitter being released, or more/less of a receptor responding in the postsynaptic membrane? What specific mechanisms are occurring in that compartment?

Question 6

In primary cell cultures, what do neurons synapse on?

Answer 6

any presynaptic neuron will be postsynaptic to another neuron (synapses) and to its own axon terminal (autapses)

Question 7

Are GABA B receptors known to be presynaptic or postsynaptic?

Answer 7

presynaptic

Question 8

Are GABA A receptors known to be presynaptic or postsynaptic?

Answer 8

postsynaptic

Question 9

What is WIN?

Answer 9

CB1 receptor agonist

Question 10

What is baclofen (Bac)?

Answer 10

GABA B receptor agonist

Question 11

What is GABA?

Answer 11

GABA A receptor agonist

Question 12

What is bicuculline (Bic)?

Answer 12

GABA A receptor antagonist

Question 13

What does a change in paired pulse ratio (PPR) usually indicate?

Answer 13

99% of the time this can only happen if there is a change in the number of vesicles released from presynaptic terminal

Question 14

What is depolarization suppression of inhibition (DSI)?

Answer 14

form of short-term synaptic plasticity that involves the calcium-dependent release of a retrograde messenger on postsynaptic depolarization