The document discusses several autacoids including histamine, bradykinin, 5-hydroxytryptamine (5HT), eicosanoids, and platelet activating factor (PAF). It describes their synthesis, mechanisms of action, functions, and pharmacological properties. Histamine is involved in allergic responses and acts on H1 and H2 receptors. Bradykinin causes pain and vasodilation. 5HT is involved in platelet aggregation and gastrointestinal motility. Eicosanoids like prostaglandins are lipid-derived autacoids formed from arachidonic acid. PAF causes potent vasodilation and increases vascular permeability.