Comparison of the after discharges induced by electrical stimulation of the prefrontal cortex in urethane- and ketamine-anesthetized mice.

OBJECTIVE The study aims to compare the effects of urethane and ketamine anesthesia on kindling-induced after discharges (AD). MATERIALS AND METHODS We divided forty 4-6 week old female C57BL/6J mice into two groups: one group was anesthetized with urethane (n = 20) and the other with ketamine (n = 20). Kindling was with an electrical stimulation (ES) consisting of a 1-s pulse train of 60 1-ms biphasic pulses at an initial intensity of 700 µA, delivered to the pre-frontal cortex every minute. Ten to fifteen minutes after the first AD was induced, identical electrical stimuli were delivered every 10 minutes for 200 minutes. EEG was continuously recorded from 15 minutes before the first ES until 10 minutes after the last ES. The EEG wave spectrum was analyzed by Fast Fourier Transform and the power spectrum densities (PSDs) of the δ, θ, α, β and γ bands were calculated. EEG wave amplitude was assessed using the root mean square value (RMS). RESULTS In the urethane group, an initial AD was induced in 70% of mice following 39 ES. In the ketamine group, an initial AD was induced in 60% of mice following 74 ES. The changes in EEG spectra were similar in both groups. Pre-AD, EEG waves predominantly consisted of δ and θ components. During AD, γ and β components increased significantly (p < 0.05). Post-AD, β and γ components decreased and the δ: θ ratio increased to pre-AD levels. CONCLUSIONS Our data suggest that AD can be induced by kindling stimulation of the pre-frontal cortex in mice under either urethane or ketamine anesthesia.