Autacoids or "autocoids" are biological factors which act like local hormones, have a brief duration, act near the site of synthesis, and are not blood borne. These regulating molecules are also metabolised locally. So the compounds are produced locally, they act locally and are metabolised locally. Autacoids can have many different biological actions. Some autacoids for instance are primarily characterized by the effect they have upon smooth muscle

Smooth muscle

Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...

. With respect to vascular smooth muscle

Vascular smooth muscle

Vascular smooth muscle refers to the particular type of smooth muscle found within, and composing the majority of the wall of blood vessels.Vascular smooth muscle contracts or relaxes to both change the volume of blood vessels and the local blood pressure, a mechanism that is responsible for the...

, there are both vasoconstrictor and vasodilator autacoids.

Vasodilator autacoids can be released during periods of exercise. Their main effect is seen in the skin, allowing for heat loss.

The word autacoids comes from the Greek "Autos" (self) and "Acos" (relief, i.e. drug). These are local hormones and therefore have a paracrine effect. Some notable autacoids are: eicosanoid

Eicosanoid

In biochemistry, eicosanoids are signaling molecules made by oxidation of twenty-carbon essential fatty acids, ....

s, angiotensin

Angiotensin

Angiotensin, a peptide hormone, causes blood vessels to constrict, and drives blood pressure up. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex...

, neurotensin

Neurotensin

Neurotensin is a 13 amino acid neuropeptide that is implicated in the regulation of luteinizing hormone and prolactin release and has significant interaction with the dopaminergic system...

, NO (nitric oxide

Nitric oxide

Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...

), kinin

Kinin

A kinin is any of various structurally related polypeptides, such as bradykinin and kallikrein. They are members of the autacoid family.They act locally to induce vasodilation and contraction of smooth muscle.It is a component of the kinin-kallikrein system....

s, histamine

Histamine

Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...

, serotonin

Serotonin

Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...

, endothelin

Endothelin

Endothelins are proteins that constrict blood vessels and raise blood pressure. They are normally kept in balance by other mechanisms, but when they are over-expressed, they contribute to high blood pressure and heart disease....

s, palmitoylethanolamide

Palmitoylethanolamide

Palmitoylethanolamide is an endogenous fatty acid amide, belonging to the class of endocannabinoids. PEA has been demonstrated to bind to a receptor in the cell-nucleus and exerts a great variety of biological functions related to chronic pain and inflammation. The main target is thought to be...

, etc.