Lecture 5: Synaptic Transmission

Question 1

What are the differences between an electrical synapse and a chemical one?

Answer 1

Electrical synapses transfer signals via gap junction, whereby a protein gaps the junction between nerve cells, whereas in a chemical synapse, the release of neurotransmitters into the synaptic cleft forms the bases of interneuronal communication.

Question 2

Name the two main groups of neurotransmitter, describe them and give some examples.

Answer 2

(1) Classical Neurotransmitters: biogenic amines (e.g. acetylcholine, dopamine, serotonine), amino acids (e.g. GABA, Glutamate) or nucleotides (e.g. Adenosine, ATP).
(2) Peptides: more complex molecule types; chains of aminoacids (if more than 100, it’s a protein); depending on where they are found in the body, they can be either neurotransmitters or hormones. Examples are oxytocin, insuline.

Question 3

What is the main difference between noradrenergic and dopaminergic neurons?

Answer 3

In noradrenergic neurons there is an additional enzyme that transforms tyrosine into L-Dopa.

Question 4

Which neurotransmitter is mainly excitatory and which one is mainly inhibitory in the CNS?

Answer 4

Glutamate is the main excitatory transmitter, while GABA is the main inhibitory transmitter.

Question 5

Name respectively two examples of neurotransmitters involved in fast point-to-point signaling and slow regulatory signaling.

Answer 5

Fast: acetylcholine (nicotinic!) and glutamate.

Slow: neuropeptides, monoamines (e.g. dopamine).

Question 6

Name the four major groups of receptors, their main features and / or respectively an example.

Answer 6

(1) Ligand-gated ion channels (e.g. nicotinic); timescale: milliseconds
(2) G-protein coupled receptors (e.g. muscarinic); slower, timescale: seconds
(3) Kinase-linked receptors (e.g. cytokine); related to phosphor; slower, timescale: hours
(4) Nuclear receptors (e.g. oestrogen); modify gene transcription; slowest, timescale: hours

Question 7

How many dopamine receptors are discovered so far? Which are inhibitory and which are excitatory?

Answer 7

There are five discovered (D1-D5), with D1 and D5 being excitatory and D2 being inhibitory. The remaining receptors are not defined yet.