Abstract
Caffeine is an antagonist at A1 and A2A adenosine receptors and epidemiological evidence suggests that caffeine consumption reduces the risk of Alzheimer's and Parkinson's diseases. Neuroinflammation plays a role in the etiology of these diseases and caffeine may provide protection through the modulation of inflammation. Adenosine has a known role in the propagation of inflammation and caffeine may reduce microglia activation directly by blocking adenosine receptors on microglia. Chronic neuroinflammation is associated with an increase in extracellular levels of glutamate and drugs that limit the effects of glutamate at neuronal receptors have been shown to indirectly reduce the neuroinflammatory response of microglia cells. A1 and A2A receptors have been shown to regulate the pre-synaptic release of glutamate, therefore, caffeine may also reduce neuroinflammation via its ability to regulate glutamate release. Caffeine was administered at various doses to young rats with experimentally induced neuroinflammation by chronic infusion of lipopolysaccharide (LPS) over two or four weeks into the 4th ventricle and to aged rats with naturally elevated levels of microglia activation. Caffeine attenuated the number of activated microglia within the hippocampus of animals with LPS-induced and age-related inflammation.