Rat sleep and EEG analyses

Data analyses were based on the two aims of the study which were to (1) quantify the changes in EEG sleep in those exposed to ethanol during adolescence compared to controls as adults at baseline following ethanol exposure and (2) test the effects of two doses of gabapentin on sleep and slow wave parameters in the ethanol and control treatment groups. Slow wave sleep (SWS) was visually identified as synchronized slow wave activity (1–4 Hz) during the 5-h EEG recording sessions that included baseline, saline injection control, gapabentin 30 mg/kg, and gabapentin 120 mg/kg. Increases in EEG power of at least twice the amplitude of waking baseline EEG power lasting longer than 8 s were counted as episodes of SWS. Sleep patterns were analyzed by (1) determining the onset latency of the first episode of SWS, (2) calculating the mean duration of all episodes of SWS, and (3) counting the total number of instances of SWS. The onset of the first SWS episode was identified from the raw EEG as the first transition from low-amplitude high-frequency EEG to SWS (high-amplitude low-frequency EEG) and lasting at least 8 s. Alcohol vapor and control animals were compared on the three sleep measures at baseline following ethanol exposure using a one-way ANOVA and following gabapentin using a 2 (alcohol vs. control) X 3 (saline, gabapentin 30, gabapentin 120) ANOVA. Significance was set at p < 0.05.

The 5-h EEG was also analyzed for spectral characteristics. Raw EEG signals were amplified (50% gain), band-pass filtered (0.53–70 Hz), digitized at a rate of 256 Hz, and then transferred to an IBM-compatible PC. A Fourier transform of 4 s epochs was used to generate the power spectrum. Mean power density was quantified in micro V²/octave and peak frequency was calculated in hertz. Individual spectral epochs were averaged and compressed into two frequency bands: to assess power in delta (1–4 Hz) and theta (4–8 Hz) frequency ranges. EEG spectra were identified as containing artifact when average cortical power was > 2000 micro V²/octave. Artifact epochs were excluded only after visual analysis of the raw EEG and spectral distributions. Mean spectral power within each band was calculated from the first slow wave sleep epoch and an average calculated for all SWS epochs over the entire 5-h recording session. These analysis procedures have been described previously (Ehlers and Havstad 1982). Alcohol vapor and control animals were compared at baseline following ethanol exposure for the two frequency bands using a one-way ANOVA and following gabapentin using a 2 (alcohol vs. control) X 3 (saline, gabapentin 30 mg/kg, gabapentin 120 mg/kg) ANOVA. Significance was set at p < 0.05.