A neurohormone is any hormone produced and released by neuroendocrine cells (also called neurosecretory cells) into the blood. By definition of being hormones, they are secreted into the circulation for systemic effect, but they can also have a role of neurotransmitter or other roles such as autocrine (self) or paracrine (local) messenger.
The hypothalamus produces releasing hormones and neurohypophysial hormones in specialized hypothalamic neurons which extend to the median eminence and posterior pituitary. The adrenal medulla produces adrenomedullary hormones in chromaffin cells, cells which are very similar in structure to post-synaptic sympathetic neurons, even though they are not neurons they are derivatives of the neural crest.
Enterochromaffin and enterochromaffin-like cells, both being enteroendocrine cells, are also considered neuroendocrine cells due to their structural and functional similarity to chromaffin cells, although they are not derivatives of the neural crest. Other neuroendocrine cells are scattered throughout the body.
Releasing hormones also known as hypophysiotropic or hypothalamic hormones are synthesized by different kinds of specialized neurons in the hypothalamus. They are then transported along neuronal axons to their axon terminals forming the bulk of the median eminence, where they are stored and released into the hypophyseal portal system. They then rapidly reach the anterior pituitary where they exert their hormonal action. The residual hormones pass into the systemic circulation where they are diluted, degraded and have comparatively little effects. The synthesis, control, and release of those hormones is co-regulated by hormonal, local and synaptic signals (neurotransmitters). The neurons secreting various hormones have been found to discharge impulses in burst, causing a pulsatile release which is more efficient than a continuous release. Hypophysiotropic hormones include:
- Thyrotropin-releasing hormone
- Corticotropin-releasing hormone
- Growth hormone-releasing hormone
- Gonadotropin-releasing hormone
Neurohypophysial hormones are synthesized in the magnocellular secretory neurons of the hypothalamus. They are then transported along neuronal axons within the infundibular stalk to their axon terminals forming the pars nervosa of the posterior pituitary, where they are stored and released into the systemic circulation. The synthesis, control, and release of those hormones is co-regulated by hormonal, local and synaptic signals. Neurohypophysial hormones include:
This is through this pathway that the vast majority of oxytocin and vasopressin hormones reach the systemic circulation.
Adrenomedullary hormones are catecholamines secreted from the adrenal medulla by chromaffin cells, neurosecretory cells connected to the central nervous system. The synthesis, storage (in chromaffin cells) and release of catecholamines is co-regulated by synaptic input from their respective pre-synaptic sympathetic neurons, as well as hormonal and local inputs. The adrenomedullary hormones are:
Enterochromaffin cells in the epithelia lining the lumen of the digestive tract secrete serotonin, while enterochromaffin-like cells at the stomach glands secrete histamine. Their synthesis, storage, and release of hormones is co-regulated by hormonal, local and nervous inputs.
- Purves, William K.; David Sadava; Gordon H. Orians; H. Craig Heller (2001). Life: The Science of Biology (6th ed.). Massachusetts: Sinauer Associates. p. 718. ISBN 0-7167-3873-2.
- Nelson. 2005 An Introduction To Behavioral Endocrinology, Third Edition
- Purves et. al. p. 714.
- Unsicker, K; Huber, K; Schütz, G; Kalcheim, C (Jun–Jul 2005). "The chromaffin cell and its development.". Neurochemical research 30 (6–7): 921–5. doi:10.1007/s11064-005-6966-5. PMID 16187226.
- Andrew, A (June 1974). "Further evidence that enterochromaffin cells are not derived from the neural crest". Journal of embryology and experimental morphology 31 (3): 589–98. PMID 4448939.
- J Meites; W E Sonntag (April 1981). "Hypothalamic Hypophysiotropic Hormones and Neurotransmitter Regulation: Current Views". Annual Review of Pharmacology and Toxicology. 21: 295-322: 295. doi:10.1146/annurev.pa.21.040181.001455.
- Nillni, EA (April 2010). "Regulation of the hypothalamic thyrotropin releasing hormone (TRH) neuron by neuronal and peripheral inputs". Frontiers in neuroendocrinology 31 (2): 134–56. doi:10.1016/j.yfrne.2010.01.001. PMC 2849853. PMID 20074584.
- Brown, A. G. (2001). Nerve cells and nervous systems : an introduction to neuroscience. London: Springer. p. 200. ISBN 3540760903.
- Burbach, JP; Luckman, SM; Murphy, D; Gainer, H (July 2001). "Gene regulation in the magnocellular hypothalamo-neurohypophysial system". Physiological reviews 81 (3): 1197–267. PMID 11427695.
- Chung, KF; Sicard, F; Vukicevic, V; Hermann, A; Storch, A; Huttner, WB; Bornstein, SR; Ehrhart-Bornstein, M (October 2009). "Isolation of neural crest derived chromaffin progenitors from adult adrenal medulla". Stem cells (Dayton, Ohio) 27 (10): 2602–13. doi:10.1002/stem.180. PMID 19609938.
- Gasman, S; Chasserot-Golaz, S; Bader, MF; Vitale, N (October 2003). "Regulation of exocytosis in adrenal chromaffin cells: focus on ARF and Rho GTPases". Cellular signalling 15 (10): 893–9. doi:10.1016/S0898-6568(03)00052-4. PMID 12873702.
- Bornstein, SR; Ehrhart-Bornstein, M (December 1992). "Ultrastructural evidence for a paracrine regulation of the rat adrenal cortex mediated by the local release of catecholamines from chromaffin cells". Endocrinology 131 (6): 3126–8. doi:10.1210/en.131.6.3126. PMID 1446648.
- Prinz, C; Zanner, R; Gerhard, M; Mahr, S; Neumayer, N; Höhne-Zell, B; Gratzl, M (November 1999). "The mechanism of histamine secretion from gastric enterochromaffin-like cells". The American journal of physiology 277 (5 Pt 1): C845–55. PMID 10564076.
- Rhee, SH; Pothoulakis, C; Mayer, EA (May 2009). "Principles and clinical implications of the brain-gut-enteric microbiota axis". Nature Reviews Gastroenterology & Hepatology 6 (5): 306–14. doi:10.1038/nrgastro.2009.35. PMID 19404271.
- Haas, HL; Sergeeva, OA; Selbach, O (July 2008). "Histamine in the nervous system". Physiological reviews 88 (3): 1183–241. doi:10.1152/physrev.00043.2007. PMID 18626069.
- Rodriguez-Diaz, R; Dando, R; Jacques-Silva, MC; Fachado, A; Molina, J; Abdulreda, MH; Ricordi, C; Roper, SD; Berggren, PO; Caicedo, A (Jun 19, 2011). "Alpha cells secrete acetylcholine as a non-neuronal paracrine signal priming beta cell function in humans". Nature Medicine 17 (7): 888–92. doi:10.1038/nm.2371. PMC 3132226. PMID 21685896.
- Sandor, A; Kidd, M; Lawton, GP; Miu, K; Tang, LH; Modlin, IM (April 1996). "Neurohormonal modulation of rat enterochromaffin-like cell histamine secretion". Gastroenterology 110 (4): 1084–92. doi:10.1053/gast.1996.v110.pm8612997. PMID 8612997.