Effect of alprazolam on morphine-induced analgesia in rats.

The effects of alprazolam on the analgesic action induced by morphine are investigated. Tail-flick latency was measured in the male Wistar rats. Alprazolam within low doses(0.5 mg/kg) attenuated morphine analgesia dose-dependently. On the other hand, inhibition of morphine-induced antinociception by alprazolam decreased and diminished at high doses(1,2 mg/kg). Flumazenil (20mg/kg) and picrotoxin(2.0mg/kg) significantly antagonised the alprazolam induced-inhibition of morphine analgesia. Muscimol(2.0 mg/kg) showed a significant decrease in morphine analgesia. All drugs themselves at each dose didn't modify Tail-flick latencies except morphine(3 mg/kg). The interaction between low dose of MOR(1.5 mg/kg) and APZ(0.75-3 mg/kg) was not significantly different. The effects of alprazolam may be linked to separate subtypes of benzodiazepine receptors, but could also involve other mechanisms.