Organic Compound- Histamine

Organic Compound- Histamine  

Introduction

Many of us are frequently made aware of the physiological functions that histamine has in our immune systems. From experiences with fever, hives, sneezing, and other insufferable seasonal allergy symptoms to life-threatening allergic reactions to household pets and plants, some of us have come to associate this organic compound with late night runs to the local pharmacy and expensive visits to both the hospital emergency room and doctor’s office. Although histamine does play a crucial role in the immune system, it has other applications in the nervous and digestion systems that make it a particularly interesting organic compound to blog about.

  

History and Chemical Properties

Formally identified in the human body by both Sir Henry Dale and Sir Patrick Playfair Laidlaw at the turn of the 20th century, histamine is a member of the chemical class known as the biogenic amines. According to the Journal Food Science, key characteristics of this chemical class include functioning as 

a chemical base, low molecular weight, and the presence of aliphatic, aromatic, 

and heterocyclic structures. 

Function in the Nervous System

Histamine synthesis inside an axon

In addition to their chemical properties, the biogenic amines (also referred to as monoamines) function as neurotransmitters in the nervous system. According to the University of Texas Health Science Center at Houston, the biogenic amines can be further separated into three classes of neurotransmitters. While many are familiar with members of both the catecholamines and indolamines classes from previous courses, I was interested to learn that histamine is considered to be in its own class of neurotransmitters based upon the location and type of receptors it has inside the central nervous system.

Role of histamine in brain diseases

        The graphic to the left illustrates some of the research currently being done on
        the potential role that both histamine and location of histamine receptors in the 
        brain may play in the development of such diseases as Alzheimer's, 
        Parkinson's, and even Schizophrenia.

      
     

Function in the Digestive System

Histology slide of stomach gastric pits

Arguably one of the most important roles histamine has in the body is the role it plays in the digestive system. Once ingested food arrives in the stomach, a complex network of cells in the lining of the stomach (specifically the gastric pits)  work to secrete concentrated hydrochloric acid that will both break down 

proteins in the ingested food, change the stomach pH, and signal other organs  

further down the alimentary canal (like the duodenum) that digestion is about 

to take place.

 

 

 

 

 

 

 

Histology slide of enteroendocrine cells

 Secreted by enteroendocrine cells inside the stomach gastric pits, histamine along with other biogenic amines act as paracrines and signal parietal cells located in the gastric pits to secrete the hydrochloric acid necessary to carry out the rest of digestive process.

 

Gastric acid secretion and histamine

The diagram to the left illustrates the complex role histamine plays in both  gastric acid secretion and the beginning of the digestive process taking place inside the stomach and continuing into the duodenum.











Conclusion

Despite being associated primarily with insufferable seasonal allergies, histamine has many other applications within the human body. From helping jumpstart the digestive process in the stomach to transmitting nerve signals in the brain, this organic compound is an integral part of our of bodies. 

-Hart Linker