TABLE 1

Tolerance to the analgesic effect of morphine does not develop in GluR5 KO mice On day 1, ED₅₀ values (milligrams per kilogram) for morphine with the 95% CI were determined in WT and GluR5 KO mice (n = 8) via a cumulative dose-response assessment after measurement of TTW latencies at 55°C. Next, morphine was injected subcutaneously 20 mg/kg b.i.d. on day 1, 40 mg/kg t.i.d. on day 2, and 80 mg/kg t.i.d. on day 3. On day 4, the ED₅₀ determination for morphine was repeated.