You probably just used too high a dose of caffeine. If you have time, the
thing to do is to try a variety of doses (all smaller than the one you tried
the first time). Try using concentrations which are 5- to 10-fold apart
(e.g. 1,10, 100, 1000) to determine a dose at which there is some response
to the caffeine but that doesn't kill the little guys.
Another possibility is that there is some contamination in the drug mixture
that kills the bugs. Be sure the controls have EVERYTHING (except the
caffeine) that the drug treated guys get.
Caffeine works by antagonizing (blocking) adenosine receptors which are
proteins found on cell membranes.
--
Lauren Murphree
Linden Lab
Department of Pharmacology
University of Virginia
