Autacoids - Definition, Function, Classification and General Overview

Autacoids

What is an autacoid? What is the definition? Auto means self and Akos means remedy. So autacoids basically can be defined as the chemical substances produced within the body to help in the remedy of local injuries.

Autacoids can be released by various stimuli and when released they bring about many physiological changes such as reddening of the skin, pain, itching, bronchospasm, etc. These effects can sometimes be undesirable and cause death. To prevent these autacoids antagonists are used.

Autacoids usually have very brief lifetime and act near the site of synthesis (local action).

Classification

1) Decarboxylated amino acids

a) Histamine

b) Serotonin

2) Polypeptide

a) Angiotensin

b) Plasmakinin

c) Vasopressin

d) Vasoactive Intestinal Polypeptide

e) Substance P

f) Slow reacting substance of anaphylaxis

3) Eicosanoid

a) Leukotrienes

b) Thromboxanes

c) Prostaglandins

Now it has been discovered that some autacoids are also found in nervous tissues. These are:

1. Histamine

2. Serotonin ( H hydroxytryptamine)

3. Prostaglandin

In the nervous tissues these autacoids function as neurotransmitters.

What’s the difference between autacoids and hormones?

1. Autacoids are produced by virtually all cells but hormones are produced by specific cells. Eg, insulin can only be produced by B cells of islets of Langerhans of pancreas.

2. Autacoids mainly act locally, ie, act near their site of synthesis but hormones are transported through the blood and act at distant target tissues.

Having said that, there are some hormones which can act as autacoids. For example, prostaglandins! Prostaglandin is a local hormone which also acts as an autacoid! This makes me want to say, “What’s there in a name?”!

So generally speaking, what’s the function of autacoids?

They take part in:

1. Inflammation

2. Allergic reactions

3. Anaphylactic reactions( not so much)

4. Neurotransmission

5. Gastric acid secretion

6. Neuroendocrine regulation

In the central nervous system, they are responsible for

1. Wakefulness

2. Decreased Appetite

3. Regulation of drinking

4. Regulation of temperature

5. Secretion of ADH

6. Control of blood pressure

7. Perception of pain.

We’ll discuss more about autacoids in the coming future. So stay tuned!