Synergistic interaction between mazindol, an anorectic drug, and swim-stress on analgesic responses in the formalin test in mice.

The present study examined the interaction between mazindol (MZ), an anorectic drug extensively used in Brazil and opioid/non-opioid endogenous analgesic systems activated by swim-stress. Further, the role of opioid, dopamine and N-methyl-D-aspartate (NMDA) receptors in mediating the analgesic effect was evaluated. The stress-induced analgesia of a 3-min swimming at 32 degrees C (opioid/non-opioid) and 20 degrees C (non-opioid) were assessed using the formalin test. Male Swiss mice were intraperitoneally injected with naloxone (1.0 mg/kg), sulpiride (3.0 mg/kg), MK-801 (0.075 mg/kg) or saline/vehicle 15 min prior, and with MZ (0.5 mg/kg) or saline/vehicle 5 min prior to swimming. The dose of MZ (0.5 mg/kg) did not cause analgesic effect, however, the association of MZ and swim-stress at both temperatures displayed synergistic interaction on analgesia that was blocked by sulpiride and MK-801 but not by naloxone. The present results suggest that MZ and swim-stress acted synergistically on analgesic responses, involving mainly the non-opioid component and possibly mediated by dopamine D2 receptors and NMDA receptors.