Figure 4. Time course of electroencephalographic effect of propofol administered (study 1) on three occasions in emulsion and lipid-free vehicle in a typical rat. The continuous line represents the spline fit to the data. Propofol administered in emulsion exhibits a rapid and evanescent effect-time profile characterized by sharp peaks and troughs. Propofol administered in lipid-free formulation results in a more sluggish effect-time profile characterized by blunted peaks and troughs. (A) 6.25 mg [center dot] min sup -1 [center dot] kg sup -1 propofol in emulsion formulation. (B) 6.25 mg [center dot] min sup -1 [center dot] kg sup -1 propofol in lipid-free formulation. (C) 10 mg [center dot] min sup -1 [center dot] kg sup -1 propofol in lipid-free formulation.