Time-course of brain ethanol levels and the acoustic startle response in the rat following the acute administration of ethanol

It is known that ethanol administration inhibits the acoustic startle response, but whether this sensitivity varies within-session has not been investigated. The purpose of the present study was to compare the time-course of ethanol levels in brain with alterations in the acoustic startle response. Three experiments were conducted in adult male Sprague-Dawley rats. 1) Ethanol concentrations in brain were determined by microdialysis following the acute administration of 0.3, 1.0 and 3.0 g/kg ig of ethanol. 2) The effect of ethanol on the acoustic startle response was determined after the same doses. 3) The acoustic startle response was determined during two time periods, at 2-18 and 30-46 minutes, after ethanol administration to evaluate periods of ascending and descending ethanol levels. In expt. 1, brain levels of ethanol rose rapidly, peaking within 4-8 minutes following all doses. In expt. 2, ethanol administration reduced the acoustic startle response in a dose-related manner; all doses significantly reduced the response. In expt. 3, prepulse inhibition was diminished by ethanol during a very short period immediately after ethanol administration, whereas the acoustic startle response was inhibited only during later times. These data indicate that the acoustic startle response was exquisitely sensitive to ethanol, even at doses as low as 0.3 g/kg. In addition, prepulse inhibition was selectively disrupted immediately after ethanol administration, which suggests that this phenomenon may accompany the short-lived ascending limb of the brain ethanol curve. Supported by AA 12356 (DL) and AA11997.