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Module 10: Figure magnocellular neurons

The magnocellular neurons of the hypothalamus.

The magnocellular neurons, which are located within the ON and PVN regions of the hypothalamus, are typical neurosecretory cells. Each MCN has 2–4 dendrites and this somatic/dendritic region contain 15000 vesicles of oxytocin (OT) or 60000 vesicles of vasopressin (VP). The long axons of these two neurons extend down into the posterior pituitary where they divide into a large number of terminals (2000/cell) each of which have approximately 250 vesicles that contain 85000 molecules of oxytocin or vasopressin that are released into the blood during activation. Pituicytes wrap around these endings reducing their access to the blood vessel, but this restriction is removed during secretion. Information for this figure was taken from Leng and Ludwig 2008.