Figure 2. The analgesic effect of clonidine after chronic treatment of dexmedetomidine or clonidine. Rats were implanted with osmotic pumps set to deliver dexmedetomidine, 5 micro gram *symbol* kg sup -1 *symbol* h sup -1, or clonidine, 15 micro gram *symbol* kg sup -1 *symbol* h sup -1. A third cohort of rats were sham-operated and represented an untreated control group. After 7 days the analgesic effect of clonidine, 150 micro gram *symbol* kg sup -1, was determined. Data were analyzed by analysis of variance and post hoc Scheffe test where appropriate. n = 9 or 10 per group. *P < 0.05 compared with control value.