Radioelectroencephalography (Tele-Stereo-EEG) in the rat as a pharmacological model to differentiate the central action of flupirtine from that of opiates, diazepam and phenobarbital.

Chronic implantation of 4 bipolar concentric electrodes into frontal cortex, thalamus, striatum and reticular formation allowed repeated recordings of field potentials from freely moving rats. After radiotransmission the signals were quantitatively evaluated by spectral power analysis. The power in particular frequency bands changed in the presence of drugs in a characteristic manner and allowed us to describe the central action of analgesics in comparison with diazepam and phenobarbital. Analysis of the data showed that the action of diazepam was mainly confined to alpha 1 and beta 2 frequencies whereas tramadol acted predominantly on the theta and alpha range. Buprenorphine and morphine most consistently influenced the alpha 2 frequencies. Whereas buprenorphine and tramadol (2 opiate drugs) showed a striking similarity to the action of morphine in corresponding brain areas the minor tranquilizer diazepam and the anticonvulsive phenobarbital could clearly be separated from them. Flupirtine, a new analgesic not suspected of an opiate-like action profile, did not resemble any of them and thus could be confirmed to have a different mode of action.