Comparative electroencephalographic evaluation of anxiolytics afobazol and diazepam in MR and MNRA inbred rats with different anxiety levels

The effects of two anxiolytic drugs, diazepam (10 mg/kg, i.p.) and afobazole (20 mg/kg, i.p.) on the EEG features was studied in MR and MNRA rats with different emotionality and anxiety levels in order to reveal an EEG marker of the anxiolytic action. For this purpose, 840 EEG parameters from 24 neocortex sites were determined and analyzed. In MR (but not in MNRA) rats, both diazepam and afobazole decreased the number of EEG parameters reliably changed upon the emotional-pain stress related to the intraperitoneal injections of 0.9% NaCl. Afobazole increased the theta-rhythm power in the spectral band of 4.75-7.25 Hz in MR rats, and in the band of 4.75-5.75 Hz in MNRA rats. Diazepam did not change the theta activity in MR rats, while decreasing it in the band of 6.00-7.25 Hz for MNRA rats. In addition, diazepam increased the spectral power in a broad frequency range of alpha and beta rhythms (8.75-17.25 Hz) in the rats of both lines, while afobazole did not produce such action. Common effects include a decrease in the spectral power within a narrow frequency band (7.5-8.5 Hz) at the boundary between theta and alpha regions. It is suggested that the latter effect can be used as the EEG marker of the anxiolytic action. The biopotential coherency in this frequency band was reduced in MR and MNRA rats only under the action of afobazole. The possibility of EEG changes related to the side action of anxiolytics and expediency of using the EEG markers in rats with different emotionality levels are discussed.