You can run, but you can't hide from NEUROHORMONES.

  My previous post introduced us to the mysterious focus known as Biochemistry. Today's post dives deeper into this focus, with special attention to a group of chemicals known as neurohormones.  

What is a neurohormone?
  The first portion, neuro, comes from the word "neuron". A neuron is a cell that processes and transfers information using electrical and chemical signals (5). They are what allow us to feel, like when you burn your hand on the stove. Neurons are found throughout the body in the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). Now let’s take a look at the other portion of the term (hormone).   

  Hormones are chemicals produced by specific parts of the body (known as endocrine glands) that travel to another designated body part (target tissue). Let's use birth control as an example. Everyone, both males and females, are familiar with birth control. Birth control has a wide range of compositions, but the most common is an orally prescribed hormone called progestin (4). Progestin is a hormone found in high concentration during female pregnancy. The hormone essentially tricks the body into thinking it is already pregnant, thereby preventing pregnancy after intercourse. So, this gives us an idea of what a hormone is, with progestin serving as an example. 

  Putting the two together, we are again faced with the term "neurohormone". A neurohormone is a hormone produced by a neuron in the nervous system, traveling and acting on a specific body part (target tissue). In schematic form:

A basic figure on how a neurohormone is created and released. Photo credit: Biology 8th Edition (Raven)

A basic figure on how a neurohormone is created and released.
Photo credit: Biology 8th Edition (Raven)

An example of neurohormone (oxytocin) regulation and release from the brain, traveling to target tissues to stimulate downstream hormones. Photo credit: Biology 8th Edition (Raven)

An example of neurohormone (oxytocin) regulation and release from the brain, traveling to target tissues to stimulate downstream hormones.
Photo credit: Biology 8th Edition (Raven)

What are neurohormones for? 
  Neurohormones play important roles in the regulation of other hormones. Such hormones include progestin (involved in reproduction), cortisol (involved in stress), and many more affiliated with daily body functions. Basically, neurohormones are everywhere!

  Why is this? Why are neurohormones necessary for control of other hormones? The answer is still uncertain, but many scientists believe it is due to complexity of higher organisms (6, 7). As we evolve along the phylogenetic tree, we have developed more and more complex systems. Neurohormones assist in this complexity by regulating downstream hormones.

Interesting applications:
  The study and understanding of neurohormones can give us valuable information about medicine, invasive species control, and many more applications (8, 9). For example, understanding how the neurohormone corticotropin-releasing hormone (CRH) works has helped us understand how to control appetite and cure anorexia (8). Another example is our understanding of sea lamprey gonadotropin-releasing hormone (GnRH) for development of species-specific pesticides. Most applications are biomedical, but that doesn't mean research on neurohormones should be limited to only biomedical studies. It all starts with you!

Next time:
Biochemistry? Check.
Neurohormones? Check.
Bringing it all full circle with "vampire fish".

References
1. Palkovits, M. "Distribution of chemically identified neurotransmitters, neuromodulators, and neurohormones in the central nervous system: review and considerations." Endocrinology, Neuroendocrinology, Neuropeptides(1981): 203. 
2. Perić-Mataruga, Vesna, Vera Nenadović, and Jelisaveta Ivanović. "Neurohormones in insect stress: a review." Archives of Biological Sciences58.1 (2006): 1-12. 
3. Welsh, JOHN H. "Neurohormones." The hormones 3 (1955): 97-151.
4. McCann, Margaret F., and Linda S. Potter. "Progestin-only oral contraception: a comprehensive review." Contraception 50.6 Suppl 1 (1994): S1.
5. Zuliani, Luigi, et al. "Central nervous system neuronal surface antibody associated syndromes: review and guidelines for recognition." Journal of Neurology, Neurosurgery & Psychiatry 83.6 (2012): 638-645.
6. Singh, M., and P. D. Webster. "Neurohormonal control of pancreatic secretion. A review." Gastroenterology 74.2 Pt 1 (1978): 294.
7. Haemer, Matthew A., Terry T. Huang, and Stephen R. Daniels. "Peer Reviewed: The Effect of Neurohormonal Factors, Epigenetic Factors, and Gut Microbiota on Risk of Obesity." Preventing chronic disease 6.3 (2009).
8. Yada T, Kohno D, Maejima Y, et al: Neurohormones, rikkunshito and hypothalamic neurons interactively control appetite and anorexia. Curr Pharm Des. May 23–2012.(Epub ahead of print).
9. Sower, Stacia A., Mihael Freamat, and Scott I. Kavanaugh. "The origins of the vertebrate hypothalamic–pituitary–gonadal (HPG) and hypothalamic–pituitary–thyroid (HPT) endocrine systems: new insights from lampreys." General and comparative endocrinology 161.1 (2009): 20-29.

 

Questions?  Comments?  Confusions?