Some aspects of the modern concept of neurosecretion
Rai, B.P.
Acta Anatomica 106(2): 212-215
1980
ISSN/ISBN: 0001-5180 PMID: 6155752 Document Number: 163817
Certain glandular nerve cells communicate with effector cells by hormonal mediators (neurohormones). The production of neurohormones is restricted to this specialized group of glandular neurons, which possess glandular attributes as well as attributes of conventional neurons. These glandular neurons, because of their dual nature, were called neurosecretory cells and their secretion is termed neurosecretory material. The identification of neurosecretion based upon the occurrence of apparent secretory inclusions in the neuron is not very reliable. The classical staining techniques of Gomori as well as newer Alcian blue and pseudocyanin methods are only suggestive rather than conclusive. Ultrastructurally, the classical neurosecretory neurons may be distinguished as having neurosecretory materials as prominent content of membrane-bound granules of varying size ranges and of varying, usually high, electron density. Intermingled with typical proteinaceous granules are small electron-lucent vesicles in dense aggregate. These are considered as packets of acetylcholine, helping in the release of neurohormones. The secretory material contains active principles regulating multiple and diverse target cells via a circular channel exemplified by polypeptides, e.g., vasopressin and oxytocin, bound to carrier proteins (neurophysins). Various physiologic traits, e.g., color change in crustaceans, tanning of the integument of insects, water balance in vertebrates, growth and regeneration in annelids, liberation of the tropic hormones from the adenohypophysis by the so-called releasing factors are regulated by the neurohormones from the CNS.