Week 2: Neurotransmitters

Question 1

Defintion of a neurotransmitter (NT)

Answer 1

A substance released from a nerve ending by a nercve impulse, diffusing across the synapse, affecting transfer of impulse from 1 neurone to another

Question 2

Classes of neurotransmitters

Answer 2

• Conventional
• Neuropeptides
• Gases

Question 3

Criteria for Conventional NT

Answer 3

• Must be synthesised via precursors/enzymes in presynaptic terminal
• Must be localised + stored in vesicles in presynaptic terminal
• Can be released from presynaptic terminal in response to electrical activity requiring Ca2+ influx mediated by action potentials
• Activity where specific receptors for the released NT must be present on the postsynaptic cell
• Must be able to be removed to prevent overstimulation/destiumlating the postsynaptic cell

Question 4

Examples of Conventional NTs

Answer 4

• Acetylcholine (ACh)
• Catecholamine (biogenic amines)

Question 5

Neuromodulators (NM)

Answer 5

• Chemicals that modulate the activity of neurons in response to a NT
• Typically released diffusely + act on multiple neurons
• Much slower but longer activity to enhance/decrease physiological response that typically act on GCPR
• Longer activity also influenced by limited uptake/enzyme degredation

Question 6

Examples of NM

Answer 6

• Dopamine in some cases
• Serotonin
• Histamine
• All peptides
• Gases
• Steroids, prostaglandins

Question 7

Peptides as NTs

Answer 7

• Can be 3-200 aa residues directly encoded by the genome
• <50 residues = peptide, >50 residues = proteins

Question 8

Examples of peptides as NTs

Answer 8

• Enkephalins
• Bradykinin
• Glucagon

Question 9

Enkephalins

Answer 9

• Short peptide structures typically involved in pain sginaling, normally pentapeptides
• Examples include: (Structure)
  + Met-enkephalin (Tyr-Gly-GLy-Phe-Met)
  + Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu)

Question 10

Bradykinin

Answer 10

• Nonapeptides that are inflammatory mediators via B1 + vasodilation via B2 receptors
• Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg

Question 11

Glucagon

Answer 11

• Increases the conversion and release of glycogen into glucose
• 29 aa polypeptide
• Human glucagon: His-Ser-Gln-Gly-Thr-Phe-Ser-Asp-Tyr-Ser-Lys-Tyr-Leu-Asp-Ser-Arg-Arg-Ala-Gln-Asp-Phe-Val-Gln-Trp-Leu-Met-Asn-Thr