Differential EEG effects of the anxiolytic drugs, deramciclane (EGIS-3886), ritanserin and chlordiazepoxide in rats

The influence of serotonergic and benzodiazepine type anxiolytic drugs on t he cortical activation and sleep-wakefulness cycle were compared by evaluat ing the effects of ritanserin and deramciclane (EGIS-3886), two 5-HT2 recep tor antagonists, and chlordiazepoxide on the electroencephalogram (EEG) in freely moving rats. Following drug administration (1, 3, and 10 mg/kg, PO f or all drugs), EEG was continuously sampled for 6 h and power spectra were calculated for every 5 s to assess changes in slow wave activity and sleep phases. In a separate test, anticonvulsant effects of the drugs were examin ed in mice. Both deramciclane and ritanserin slightly increased total time spent in deep sleep (DS) and lengthened sleep episodes. In contrast, chlord iazepoxide had a strong inhibitory action on DS, sleep time being shifted t o more superficial light sleep (LS). The incidence and length of the high v oltage spindle (HVS) episodes characteristic for the motionless, awake rat were increased at the highest dose of both deramciclane and ritanserin, whi le it was decreased by chlordiazepoxide. In mice? chlordiazepoxide had a ma rked anticonvulsant effect, while deramciclane was moderately effective and ritanserin ineffective. In conclusion, the 5-HT2 receptor antagonist anxio lytic drugs seem to be superior compared to the benzodiazepine type anxioly tic drug, chlordiazepoxide, as ritanserin and deramciclane improved sleep q uality by increasing sleep episode length and time spent in DS, while chlor diazepoxide enhanced sleep fragmentation and decreased DS.