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28 Cards in this Set
- Front
- Back
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Define Neuropeptide:
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A peptide that functions as a signalling molecule and is released from neurons
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How many amino acids are in neuropeptides typically?
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2 - 40
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How long is Neurotensin?
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13 AA
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Where is Neurotensin found?
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-Prefrontal cortex
-Hypothalamus -Midbrain |
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What is important to remember about neurotensin's location?
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It is always located with dopamine - COLOCALIZED
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Is dopamine always found with neurotensin?
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No; just the other way around.
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Is co-localization unique to neurotensin?
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No it is a characteristic of most peptide transmitters.
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What is achieved by colocalization?
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More refined, specific, and complexity of signals.
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What is neurotensin synthesized from?
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A 170 aa protein precursor that contains NT + Neuromedin N
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Where is Neurotensin's precursor sent?
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To the golgi via its hydrophobic signal sequence
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What happens to the precursor in the golgi?
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Packaging into secretory vesicles along with peptidases.
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How is Neurotensin made from its precursor?
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By processing via peptidases - they produce 1 Neurotensin + 1 Neuromedin N
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Important point to remember about the packaging of Neurotensin:
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This is not into Synaptic Vesicles, rather Secretory granules
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How are secretory granules containing Neurotensin released?
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Via the constitutory pathway
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What is the morphologic nature of the neurotensin-containing granules?
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They are electron dense - DENSE CORE
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How does neurotensin get to the nerve terminal?
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By axonal transport
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How much neurotensin is usually stored at the axon terminal?
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Low amounts - it varies.
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How is Neurotensin release from the axon terminal mediated?
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Calcium dependent
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What is required for Neurotensin release?
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Rapid firing of neurons at HIGH INTENSITY
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3 Ways that Neurotensin release is different from that of normal neurotransmitters:
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-Requires more calcium and higher intensity AP firing
-No vesicles, and the granules are not recycled or refilled -Exhibits extrasynaptic release beyond Active zone |
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What is extrasynaptic release?
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The ability of a NT to act on more than one postsynaptic neuron
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So how do Secretory vesicles filled with Neurotensin differ from normal vesicles? (3 ways)
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1. Dense cores on EM
2. 2x Larger 3. Transported to axons via secretory pathways at low and variable concentrations. |
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3 Ways that Neurotensin inactivation is regulated:
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1. Peptide cleavage via extracellular peptidases
2. Diffusion away from synapse 3. Internalization of peptide bound to its receptor |
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Do neurotensin-releasing nerves exhibit reuptake?
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No
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How does neurotensin inactivation compare to that of Glutamate and Norepinephrine?
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-Less directed
-Lasts longer -Lower fidelity |
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What is the nature of Neurotensin's receptor binding?
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High affinity b/c the molecule is so big.
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Receptor type for neurotensin
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G-protein linked
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How is neurotensin activity related to dopamine?
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Activation of Dopamine auto-receptors (to inhibit dopamine's presynaptic release) enhance NT release.
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