Final Flashcards
What is the difference between neuropeptides and peptide hormones?
THey are released from different cell types. Neuropeptides from neurons and peptide hormones from other cells.
Name the major categories of mammalian neuropeptides (6)
Hypothalamic releasing hormones, neurohypophyseal peptides, adenohypophyseal peptides, opioid peptides, gastrointestinal peptides, growth factors
Compare and contrast neuropeptide vs. neurotransmitter synthesis
NT: amino acid precursor and synthesizing enzymes are packaged into synaptic vesicles in the cell body, then transported to the terminal where NT is synthesized.
NP: large pre-prohormones are synthesized, containing the active peptides. Proteolytic enzymes cut at specific sites to release the prohormones which are then packaged into secretory vesicles and converted to hormones. This is followed by axonal transport.
How are opioid peptides made and what are their precursors?
They are made by cleaving large pre-prohormones containing the biologically active peptides. Precursors are proopiomelanocortin, proenkephalin and prodynorphin.
Compare small and large vesicles with respect to NT and NP colocalization.
Small synaptic vesicles only contain NT while large secretory vesicles can either contain just NP or NP+NT.
Describe the localization of Substance P
Found throughout the brain including in the lateral dorsal tegmental nucleus with ACh, and in the brainstem with epinephrine.
Describe the localization of Somatostatin
Found throughout the brain including with GABA in the neocortex, dentate gyrus and hippocampus.
Describe the localization of oxytocin
Cell bodies in supraoptic nucleus and paraventricular nucleus, extend throughout brain including to the posterior pituitary
Where is POMC made?
The arcuate nucleus and the posterior pituitary
What are the criteria for defining a chemical as a neuromodulator (6)?
- it must not act transsynaptically
- it must be present in physiological fluids
- it must have access to site of modulation
- it must affect neuronal activity
- its direct application should mimic effects of increasing endogenous levels
- it must have inactivating mechanisms
In what ways can NPs act on pre and postsynaptic neurons?
NP can (1) bind to the same post receptors as NT or (2) to their own post receptors, or (3) to pre receptors to modulate their own activity. NP can (1) bind to synaptic receptors to modulate their sensitivity, (2) regulate Ca2+ or K+ channels to affect cell electrophysiology, (3) bind to non-synaptic receptors to affect second messenger/mRNA/protein synthesis or (4) bind Ca2+/K+ channels at terminals to affect NT release
What is released when a cell is stimulated infrequently?
NT from synaptic vesicles
What is released when a cell is stimulated frequently?
Larger secretory vesicles containing NP+NT as well as synaptic vesicles containing NT
Compare the effect of NP and NT on post response
NT -> brief response
NP -> prolonged response
Explain how the interaction of a NT and NP can increase the effect on the post cell (2).
Together they increase second-messenger activity. Both bind to their receptors, activating more second-messenger than either would on their own. They can also increase protein synthesis.
