Neuropeptides

Question 1

Tachykinins (TAC)

Answer 1

Largest family of neuropeptides
Conserved COOH terminal, variable N-terminal.
Include substance P, neuropeptide Y and neurokinin A/B.
Landmark events in the history of tachykinins include the discovery of substance P and the human NK1 receptor, and the discovery of the NK1 antagonist aprepitant, used for nausea and vomiting.

Question 2

Neuropeptide Y

Answer 2

Belongs to TCA family.
36-amino acid neuropeptide acting in the brain and ANS.
In the brain, it is produced by the hypothalamus and causes an increase in food intake and fat storage, and a decrease in anxiety, BP and pain perception. It also affects the circadian rhythm.
In the ANS, it acts as a strong vasoconstrictor.

Question 3

NPY receptors

Answer 3

NPY1, 5 and 6 receptors are Gi-coupled.
NPY2 and 4 receptors are Gq-coupled.
NPY1 and 5 receptors are orexigenic, while 2 and 4 are anorexigenic.
NPY decreases EPSP amplitude.
NPY receptor agonists modulate glutamate-induced Ca2+ responses.

Question 4

Substance P

Answer 4

Belongs to TCA family.
11-amino acid peptide acting on NK1 receptors.
SP is involved in nociceptive signalling. Capsaicin is an antagonist clinically used as an analgesic and anti-inflammatory agent to reduce pain associated with arthritis and neuralgia.
SP promotes wound healing.
SP acts as a NO-dependent vasodilator, inhibiting Ca channels.

Question 5

Brain-derived neurotrophic factor (BDNF)

Answer 5

Mediates neurogenesis, synaptogenesis and neuronal survival.

Question 6

Somatostatin

Answer 6

Targets potassium channels and sodium-hydrogen exchangers, and affects PLC calcium signalling.
Exist in two active forms, as 14-aa or 28-aa.
The shorter 14 isoform works primarily in the brain, controlling motor function, sleep, and sensory and cognitive processes.
The longer 28 isoform operates in the GIT, where it inhibits gastric acid secretion.
SST is onvolved in Alzheimer’s, Parkinson’s, depression and schizophrenia.