NIEHS Environmental Factor – January 2012: Intramural papers of the month:
A recent study published by NIEHS scientists suggests how and where caffeine might act in the brain to increase cognitive function. Previous research shows that caffeine acts by blocking the inhibitory effects of adenosine on cyclic adenosine monophosphate AMP production in the brain. This study represents the first demonstration of long-lasting synaptic plasticity induced by in vivo exposure to caffeine, as reported in the journal Nature Neuroscience.As a widely consumed stimulant, caffeine’s effects on synaptic transmission in the CA2 area of the hippocampus, where adenosine A1 receptors are highly enriched, were not known. Rats were divided into three groups and given doses equivalent to two large cups of coffee, a highly caffeinated energy drink, or a dose that exceeded most people’s daily consumption. All doses of caffeine strengthened the connections between neurons of CA2, but not in other areas of the hippocampus, a brain structure important for learning and memory.These results provide a pleasingly simple explanation for the common daily human experience. Adenosine levels increase in the brain during the day, inhibiting the production of cyclic AMP. Although these effects recover during sleep, caffeine accelerates recovery by blocking any residual adenosine action and strengthens the activity of CA2 synapses of the hippocampus. This discovery also raises exciting new questions about the role of CA2 neurons in brain function.Citation: Simons SB, Caruana DA, Zhao M, Dudek SM. 2011. Caffeine-induced synaptic potentiation in hippocampal CA2 neurons. Nat Neurosci; doi:10.1038/nn.2962 [Online 20 November 2011].