Supraopticohypophyseal tract

The supraopticohypophyseal tract is the component of the hypothalamohypophyseal neurosecretory pathway formed predominantly by axons of magnocellular neurosecretory neurons in the supraoptic nucleus (SON) of the hypothalamus. These unmyelinated axons descend from the supraoptic nucleus through the hypothalamus and infundibulum (pituitary stalk) to terminate in the pars nervosa of the posterior pituitary.

The supraopticohypophyseal tract carries predominantly vasopressin (antidiuretic hormone, ADH), which is synthesized in the neuronal cell bodies of the supraoptic nucleus and transported along the axons in association with neurophysins. Neurosecretory material may accumulate in axonal dilatations called Herring bodies before being released from nerve terminals adjacent to fenestrated capillaries of the posterior pituitary. Action potentials stimulate the release of ADH into the systemic circulation, where it plays a major role in water conservation and regulation of plasma osmolality.

Clinical correlate

Damage to the supraoptic vasopressin neurons or their descending axons can reduce ADH secretion and contribute to central diabetes insipidus.