Biological factors which act like local hormones, have a brief duration, act near the site of synthesis, and are not blood borne. Autacoids are primarily characterized by the effect they have upon smooth muscle. With respect to vascular smooth muscle, 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: eicosanoids, angiotensin, neurotensin, NO (nitric oxide), kinins, histamine, serotonin, endothelins, etc.
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