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Summary of Autacoids :-

Autacoids or "autocoids" are biological factors (molecules) which act like local hormones, have a brief duration, and act near their site of synthesis.The word autacoid comes from the Greek words "autos" (self) and "acos" (relief; i.e., drug). The effects of autacoids are primarily local, though large quantities can be produced and moved into circulation.[citation needed] Autacoids may thus have systemic effects by being transported via the circulation. These regulating molecules are also metabolized locally. In sum, these compounds typically are produced locally,[citation needed] act locally and are metabolized locally. Autacoids can have a variety of different biological actions, including modulating the activities of smooth muscles, glands, nerves, platelets and other tissues.

Some autacoids are chiefly characterized by the effect they have on specific tissues, such as smooth muscle. With respect to vascular smooth muscle, there exist both vasoconstrictor and vasodilator autacoids. Vasodilator autacoids are released during periods of exercise. Their main effect is seen in the skin, where they facilitate heat loss.

These are local hormones; they therefore have a paracrine effect. Some notable autacoids are: eicosanoids, angiotensin, neurotensin, NO (nitric oxide), kinins, histamine, serotonin, endothelins and palmitoylethanolamide.

Autacoids from the Greek autos (“self”) and akos (“cure”) are endogenous organic molecules with potent pharmacologic effects, that are not part of traditional immune or autonomic groups. Histamine and serotonin (5-hydroxytryptamine) are two important amine autacoids. Other autacoids, which produce paracrine type effects, include polypeptides (angiotensin, bradykinin, and kallidin), lipid-derived substances (prostaglandins, leukotrienes, and platelet-activating factor), and nitric oxide.

Histamine :-
  1. Chemical mediator derived from decarboxylation of a.a histidine, majority is stored in mast cells & basophils with minor amounts in CNS where act as neurotransmitter & enterochromaffin cells in stomach.
  2. Now days, histamine have no clinical role only in the past used in diagnosis of hyperacidity (achlorhydria), pheochromocytoma, pernicious anemia, & pulmonary function test.