Neuropeptides

What is the difference in release time between neurotransmitters and neuropeptides?

• Neurotransmitters are released rapidly within milliseconds of an action potential.

• Neuropeptides are released more slowly, taking seconds to minutes at low cytosolic Ca2+ concentrations.

Name examples of neuropeptides.

• Oxytocin

• CRH

• Neuropeptide Y

• Endorphins

What are the key characteristics of neurotransmitter action?

• Act quickly

• Have low molecular weights

• Stored in small clear vesicles

• Bind to ionotropic receptors

• Diffuse locally across an ultra-short distance to quickly interact with receptors on adjacent neurons.

How are neuropeptides stored in cells?

• Stored in large dense-core vesicles (LDCVs).

• Released less frequently compared to small clear vesicles that store neurotransmitters.

• Released at low cytosolic Ca2+ concentrations

What is the role of Neuropeptide Y (NPY)?

• Crucial for regulating food intake.

• Regulates energy metabolism.

• Helps the body adapt to chronic stress e.g. by dampening the HPA axis

What types of receptors do neuropeptides act on?

• Primarily act on G-protein coupled receptors (GPCRs).

• These receptors trigger multiple intracellular signaling cascades.

• Produce slower, longer-lasting effects

Describe the functions of the receptors acted on by NPY

• Y1 and Y5 receptors promote increased food intake, help regulate stress and anxiety, and contribute to blood vessel constriction.

• Y2 receptor reduces the release of NPY and other signals, helping to dampen activity and modulate stress responses.

• Y4 supports digestion and energy balance, while Y6 is inactive in humans.

What distinguishes neuropeptides from classical neurotransmitters?

• Neuropeptides: High potency, long-lasting effects. Not recycled back into the cell

• Classical neurotransmitters: Rapid, short-lived actions.

Describe the synthesis location of neuropeptides compared to neurotransmitters.

• Neuropeptides: Synthesized in the rough endoplasmic reticulum, modified in the Golgi apparatus. In low concentrations

• Neurotransmitters: Predominantly synthesized in the cytosol of presynaptic neuron terminals. In high concentrations

What is the primary function of somatostatin in the body?

• Plays a role in regulating:

  • Motor activity

  • Sleep

  • Sensory and Cognitive processes

  • Anxious behaviour

2 forms of the peptide, same function but act in different areas (brain and GI tract)

How do neuropeptides differ in their signaling mechanisms compared to neurotransmitters?

• Neuropeptides activate second messenger systems and modulate cell signalling pathways. Act on cells not in the immediate vicinity.

• Neurotransmitters usually act directly upon ion channels for immediate effects.

What is the role of substance P in the human body?

• Involved in the perception of pain.

• Acts as a vasodilator, promoting blood flow by dilating blood vessels.

• SP antagonists, e.g. Capsaicin can be used to reduce pain

What are the effects of high concentrations of Neuropeptide Y (NPY) in the autonomic nervous system?

• Acts as a strong vasoconstrictor.

• Influences blood pressure and promotes lipogenesis, impacting fat tissue development.

Compare the recycling of neuropeptides and neurotransmitters post-release.

• Neuropeptides undergo degradation after release and are not recycled back into the presynaptic cell.

• Many neurotransmitters, like glutamate, are actively recycled.

What impact do neuropeptides have on brain function?

• Play roles in modulating:

  • Pain perception

  • Learning and memory processes

  • Appetite regulation

  • Metabolic control

  • Reproductive behaviors

  • Social interactions.

What does the term 'Pre-Pro peptide' refer to in neuropeptide synthesis?

• A precursor form of a neuropeptide synthesized in the endoplasmic reticulum.

• Undergoes cleavage and modifications to yield the active neuropeptide.