Anxiolytic effects of dotarizine, a possible antimigraine drug

In experiments on rats in elevated plus-maze and in Opto Varimex apparatus, used for studying exploratory behavior, we observed that dotarizine (DOT), a drug with Ca2+ and 5-HT1/5-HT2-receptor antagonistic action, exerted effects suggesting anxiolytic action. The 5-HT uptake inhibitor fluoxetine (FLU) produced mainly anxiogenic effects. The simultaneous administration of DOT and FLU weakened the anxiolytic effect of DOT. The effects of the 5-HT1B/5-HT1C receptor agonist with promigraine action, m-chlorophenylpiperazine (m-CPP), indicated anxiogenic action, which was increased to a certain extent when it was combined with FLU. Some of the other 5-HT-receptor agonists and antagonists tested showed anxiogenic action and others anxiolytic action. In most cases, these effects were changed when they were administered simultaneously with FLU. DOT increased general locomotor activity and when combined with FLU this effect tended to decrease. In contrast, m-CPP decreased general locomotor activity and this effect was potentiated by FLU. DOT at the two doses used did not significantly change the rate of development of habituation, while m-CPP, buspirone and ondansetron increased it. The behavioral effects of DOT observed in all cases opposite to the same effects of the promigraine drug m-CPP suggest an antimigraine action of DOT.