Figure 6.

Propofol induced changes in the frequency of sIPSCs suggest presynaptic actions. Propofol at 10 µM evoked increases in the frequency of sIPSCs (Panel A). Picrotoxin (PTX) at both 10 µM and 20 µM blocked the propofol evoked increases. Blockade of voltage-dependent Ca⁺⁺ or Na⁺ channels by Cd²⁺ (200 µM) or TTX (300 nM), respectively, prevented propofol induced increases (brackets show no difference in propofol, p>0.05, Panel B). Thus, the presynaptic actions of propofol appear to depend on depolarization. TTX or Cd²⁺ alone reduced IPSC frequency to 61.4±16.8% and 43.4±14.0% of the control, respectively, and suggest that voltage dependent processes contributed to basal sIPSC activity. All data have been normalized to the control frequency of sIPSC before propofol. Broken line indicates control levels of activity.