Autacoids antagonists

The main mechanism of action of caffeine occurs via the blockade of adenosine receptors in the CNS. Adenosine is an autacoid, which is involved in the modulation of behavior, oxygenation of cells, and dilatation of cerebral and coronary blood vessels and indirectly inhibits the release of dopamine. The blockade of adenosine receptors by caffeine increases the activity of dopamine, which is implicated in the effects of caffeine (91). The question that arises from this observation is to know whether or not adenosine antagonists hold potential for the treatment of Parkinsonism, and further study on the adenosine receptor antagonists from medicinal plants should be encouraged. A possible source for such agents could be the medicinal flora of Asia and the Pacific, among which is the family Sapindaceae. 

Theophylline is a competitive antagonist at adenosine receptors. Adenosine can act as an autacoid and transmitter with myriad biological actions. Of particular relevance to asthma are the observations that adenosine can cause bron-choconstriction in asthmatics and potentiate immunologi-cally induced mediator release from human-lung mast cells. Inhibition of the actions of adenosine therefore also must be considered when attempting to explain the mechanism of action of theophylline. 

During hypersensitivity reactions, histamine is one of the many potent autacoids released see above), and its relative contribution to the ensuing symptoms varies widely with species and tissue. The protection afforded by histamine antagonists thus also varies accordingly. 

Ginkgolide B is a selective antagonist of platelet aggregation induced by platelet-activating factor (PAF). PAF, an inflammatory autacoid, is involved in various inflammatory, cardiovascular, and respiratory disorders. " Ginkgo extract has also displayed anti-inflam-matroy activity in a number of conditions and disease models such as colitis, arthritis, skin inflammation, and rat paw edema. " Antiinflammatory mediators have been suppressed by the extract. ... 

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