Figure 1. Effect of chronic dexmedetomidine administration on norepinephrine turnover plus/minus acute dexmedetomidine in the (A) locus coeruleus and (B) hippocampus. Rats were implanted with osmotic pumps set to deliver 3 or 10 micro gram *symbol* kg sup -1 *symbol* h sup -1 (tolerant groups) or sham-operated (naive group). On the 7th day, rats were administered 30 micro gram *symbol* kg sup -1 dexmedetomidine intraperitoneally and the turnover of norepinephrine was determined. Data are expressed as a percentage of control animals normalized to 100%. ANOVA: P < 0.0001 (hippocampus) and P < 0.005 (locus coeruleus) *P < 0.05 compared with basal state (Fisher test) (section)P < 0.0001 compared with naive group. n = 7-8 per group.