Effects of the serotonin-1A agonists buspirone and ipsapirone on field potentials in the hippocampus slice: comparison with carbamazepine and verapamil

Abstract

The serotonin-1A agonists buspirone (BU) and ipsapirone (IPSA) have been demonstrated to exert antidepressant and anxiolytic effects. Since some antidepressant drugs and the antiepileptic substance carbamazepine have calcium antagonistic properties, the interaction of BU and IPSA with carbamazepine and the organic calcium channel blocker verapamil was analyzed in the low Mg 2+ induced model epilepsy which has been shown to be suppressed specifically by organic calcium antagonists. BU and IPSA reduced the frequency of occurrence of low magnesium induced field potentials in CA1 and CA3 areas of the hippocampus slice preparation (guinea pigs) in a dose dependent manner. The subthreshold concentrations which yielded no effect were 5 μmol/1 for BU and IPSA, 10 μmol/1 for carbamazepine and 2 μmol/1 for verapamil. Combinations of these subthreshold concentrations elicited a reduction in the repetition rate of field potentials. The results indicate that BU and IPSA behave additively with verapamil and carbamazepine, which may be due to a common action on the same subtype of calcium channels. It may be assumed that besides their action on 5-HT 1A receptors BU and IPSA may also have calcium antagonistic properties.