In Vivo Dopamine Measurements in the Nucleus Accumbens After Nonanesthetic and Anesthetic Doses of Propofol in Rats

There is growing evidence that propofol acts on affective and reward processes. We designed this study to assess the effect of propofol on the concentration of dopamine in the nucleus accumbens, a main component of the mesolimbic system. The concentration of dopamine in the nucleus accumbens was assessed by using in vivo brain microdialysis in freely moving rats. A microdialysis probe was placed within guide cannulae previously placed during stereotaxic surgery. Fluid was perfused through the probe, and samples were collected every 20 min for measuring concentrations by high-pressure liquid chromatography. All rats served as their own controls and were randomized to four different doses of propofol, injected intraperitoneally: 0, 9, 60, or 100 mg/ kg, according to a within design. Compared with the baseline value, dopamine concentration was decreased at the smallest dose of 9 mg/kg, whereas concentration was largely increased at the subanesthetic (60 mg/kg) and anesthetic (100 mg/kg) doses. This increase was of the same magnitude (+90%) for subanesthetic and anesthetic doses but was more prolonged at the anesthetic dose. Data show that only subanesthetic and anesthetic doses of propofol increase the concentration of dopamine in the nucleus accumbens, as previously described with drugs of potential abuse.