Effect of anesthesia on the propagation of cortical spreading depression in rats

The effect of ip anesthesia with urethane+chloralose (U+C, 1.0 g/kg + 40.0 mg/kg) or thionembutal (TH, 40.0 mg/kg) on the velocity of propagation of cortical spreading depression was studied in adult Wistar rats. We also describe a technique for measuring the spreading depression propagation rate based on implanting insulated silver wires into the right parietal region, whose silver chloride tips are in contact with the cortical surface. The propagation rate was measured in the same animals during (mean +/- SEM, mm/min: 2.69 +/- 0.17 for U+C, N = 9, and 2.60 +/- 0.09 for TH, N = 7) and after (3.23 +/- 0.13 for U+C and 3.84 +/- 0.18 for TH) anesthesia. The rate was significantly higher for rats in the awake condition. The second administration of anesthesia to the same rats decreased the velocity of spreading depression again (2.01 +/- 0.38 for U+C, N = 7, and 2.96 +/- 0.18 for TH, N = 7). The effects of TH and U+C on the rate of propagation were reversed 24 and 48 hours after anesthesia, respectively. We conclude that the technique proposed is adequate for measuring the velocity of spreading depression in unanesthetized rats and that U+C and TH reduce the propagation velocity.