A protein that intensifies and prolongs caffeine`s kick is identified in this week`s issue of the science journal Nature.
Although caffeine is probably the world's most widely used psychostimulant, surprisingly little is known about its molecular mechanism, the journal reports. At concentrations equivalent to a few cups of coffee a day, it binds and blocks nerve cells that normally inhibit voluntary movements in the brain`s movement centre, the striatum.
Gilberto Fisone of the Karolinska Institute, Stockholm, Sweden, and colleagues found that a protein called DARPP-32 is the key to the action of coffee: mice genetically engineered to lack DARPP-32 are immune to some of its stimulatory effects.
Low doses of caffeine appear to trigger a positive feedback loop in striatal nerves: they subdue a protein called protein kinase A, which in turn keeps DARPP-32 phosphorylated. In this form, it dampens protein kinase A further. Together with other molecules in the feedback loop, they control the activity of further proteins that inhibit nerve activity, and thus keep us hyperactive.
"DARPP-32 keeps us going until the next coffee break by extending the effects of the last cup," wrote Jean-Marie Vaugeois of the University of Rouen, France, in this week's issue of Nature.
Further information about the study can be obtained from Gilberto Fisone: gilberto.fisone@neuro.ki.se.