ANAT 322 Lecture Notes - Lecture 4: Apelin, Corticotropin-Releasing Hormone, Periventricular Nucleus

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ANAT 322 Lecture 4 (Jan 20)
Dr. Stroh
Part I: Plasticity in the Magnocellular System
Morphological plasticity in magnocellular nuclei during dehydration or lactation
Oxytocin neurons
When unstimulated, not too many dendrites make contact with the cell body
When stimulated, cell bodies touch each other, along with more synaptic contacts
oMembrane apposition, dendritic bundling
Glial plasticity is the basis of morphological reorganization in the magnocellular system
Under basal conditions of hormone release, astroglial processes separate magnocellular somata
oThey fill the voids between neurons
During lactation or dehydration, the astrocytic processes withdraw, thus allowing for direct apposition
of somatic and dendritic membranes of neighbouring magnocellular neurons
oSystem is so plastic that it can regulate its own activity using glial cells
Dendritic release of secretory granules in the PVN and SON
You get release of OT from the cell body and dendrites
Autoregulation: the neurons also express receptors for the hormone
oCould lead to auto-excitation or auto-inhibition, depending on the signaling cascade
*Need to remember that these neurons express other transmitters
Part II: Other Bioactive Peptides and Colocalization in the Neuroendocrine Hypothalamus
Colocalization in the arcuate nucleus
Illustrating the diversity of the colocalization of transmitters
TH – synthetic enzyme for dopamine
ChAT – acetocholine
GRF (GHRH) – growth hormone releasing factor
Colocalization of Vasopressin (AVP) with apelin in the supraoptic nucleus
AVP stored in immense density in granules
Apelin happens to be expressed in mainly AVP neurons
oInteresting because it is an antagonist to the action of AVP
Colocalization of neuropeptides within magnocellular neurons (incomplete list)
Pituitary Adenylate Cyclase-Activating Peptide
oIn OT cells in PVN, SON, periventricular nucleus
Angiotensin II
Corticotropin releasing hormone (CRH)
Cholescystokinin (CCK in OT neurons)
Enkephalin (in OT neurons)
Dynorphin (AVP cells, packaged in the same large dense core vesicles)
Apelin (mainly in AVP cells, very widespread distribution)
oThere are a very few number of neurons that express apelin but not AVP
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