Inositol trisphosphate (IP3) receptors and epileptic seizure.

The effects of anticonvulsants and Ca2+ channel antagonists on the inositol trisphosphate (IP3) binding and IP3-induced Ca2+ release were examined in brain membrane fractions. Anticonvulsant (PHT and valproate) and Ca2+ channel antagonists (verapamil, diltiazem, flunarizine, nicardipine and cinnarizine), examined did not significantly inhibit the IP3-receptor binding. The Kd and Bmax values of the IP3 binding did not change significantly in the various brain regions of the amygdala-kindled rats, killed 10 days after the last seizure, compared to those of controls. On the other hand, PHT, PB and carbamazepine inhibited the Ca2+ releasing activity of IP3 in the cerebellar membrane fractions by approximately 20% at therapeutic concentrations.