Equivalent dipoles of FFT data visualize drug interaction at benzodiazepine receptors.

The aim of the present investigation was to study if the benzodiazepine receptor antagonist flumazenil could reverse the effects on the brain electrical activity induced by the benzodiazepine receptor agonist midazolam. The method of FFT approximation was used for this purpose. It allows the calculation of center of gravity equivalent dipoles of spectral EEG data. The results are reference independent and allow therefore a more unambiguous interpretation compared to conventional FFT data reports. Twelve subjects were investigated before and after 0.1 mg/kg and 0.2 mg/kg midazolam respectively, directly and 4 h after administration of 1 mg flumazenil. Our results imply that the application of flumazenil after midazolam sedation leads to an almost complete restoration of the brain electrical activity. However, especially in the beta frequencies above 20 Hz differences in depth of equivalent dipoles were found directly after flumazenil application as well as 4 h later. This could suggest that neuronal generators in different brain structures were responsible for the electrical activity after flumazenil administration compared to before.