Figure 2.

Daily release of spinal amino acids expressed as a percentage of day 1 resting basal levels (prior to i.p. naloxone or saline) in four groups of rats (as described in Figure 1). Samples were collected by microdialysis prior to the daily intraperitoneal injection of saline or naloxone. Daily basal spinal glutamate release increased modestly in rats with continuous morphine infusion and daily saline injections. The release was significantly elevated in rats treated with morphine infusion and daily naloxone injections on days 2 and 3. The baseline spinal release of taurine in IT-M+IP-N group was also increased significantly on day 3. Each line represents the mean±s.e.mean of six rats. *P<0.05 versus release in other groups on that day, one way ANOVA, Dunnett's t-test post hoc comparison).