Evidence for specific interactions between kavain and human cortical neurons monitored by fluorescence correlation spectroscopy

Specific interactions between a tetramethylrhodamine-labeled kavain derivat ive and human cortical neurons were found for the first time using fluoresc ence correlation spectroscopy (FCS). Human cortical neurons, cultivated in Nunc(R) chambers, were incubated with 1 nM of the dye-labeled kavain deriva tive. A total binding of 0.55 nM was found after an incubation period of 60 min. 50% of the total binding was specifically displaced in the presence o f 1 mu M non-labeled (+)-kavain. Evidence for these specific interactions w as verified by a saturation experiment. Both the non-linear Scatchard plot and the n value of 1.58 +/- 0.07 in the sigmoid Hill plot indicate binding sites with different binding affinities.