TABLE 1

Tolerance induced by morphine or naloxone in mice injected with dsAAV2-MORS196ACSTA-EGFP intrathecally

The ED₅₀ values of morphine or naloxone to inhibit the tail-flick responses were determined by the up-down method. After 2 weeks of gene transferred, animals were tested for the ED₅₀ values of morphine or naloxone and then chronically treated with morphine (10 mg/kg s.c., b.i.d. for 6 days) or naloxone (10 mg/kg s.c., b.i.d. for 6 days). The ED₅₀ values were then redetermined. The values represent the mean ± S.E.M. (n = ∼6–8).