Studying responses of live cells to agonists, antagonists and other ph
ysical stimuli offers insight into their complex membrane and internal
biochemistry. An experimental technique has been developed in which r
esponses of living cells in an inverted radial flow chamber are contin
uously monitored while being repeatedly stimulated using controlled pu
lses of a biologically active ligand. Precisely defined flow condition
s result in reproducible peaks which can be numerically analysed by co
mparison with a tracer curve obtained by substituting a dye for the st
imulus. Exploratory studies have demonstrated that the flow injection
technique can provide a novel method for kinetics of receptor binding
and cellular responses. Flow injection microscopy (FIM) allows identif
ication of biologically active ligands and their ranking based on meas
urement of the cellular responses in a short time frame. The use of FI
M for rapid drug screening, through monitoring of the initial kinetics
of cellular responses, is demonstrated on a model system.