Fig. 6. Effect of prazosin on the enhanced response to a combination of dexmedetomidine and nitrous oxide (mean ± SEM; n = 4). The administration of dexmedetomidine results in an enhanced analgesic response to nitrous oxide (black triangle; same data as in fig. 3B). Rats were pretreated with 5 mg/kg intraperitoneal prazosin (white arrow ), and the analgesic response to a combination of 70% N2O and 12.5 μg/kg intraperitoneal dexmedetomidine (white diamond ) was measured by the tail-flick latency assessed at regular intervals. Black arrow = the time of dexmedetomidine administration. MPE = maximal possible effect.