Figure 3.

Daily spinal glutamate, aspartate, taurine and serine release in the four groups measured concurrently after the injection of intraperitoneal (i.p.) naloxone (0.6 mg kg⁻¹) or saline (S). Release is expressed as the percentage of the respective daily resting, prior to i.p. naloxone or saline in rats undergoing continuous intrathecal (IT) infusion of morphine (M) (20 nmol h⁻¹) or saline (S). The increases in glutamate, aspartate and taurine from the resting release were significant on day 3 in rats with IT morphine infusion and daily i.p. naloxone injections. There was no significant change in the release of spinal serine in any group. Each line represents the mean±s.e.mean of six rats. *P<0.01 versus release in other groups on that day, one way ANOVA Dunnett's t-test comparison.